Abbriano, RM, Carranza, MM, Hogle, SL, Levin, RA, Netburn, AN, Seto, KL, Snyder, SM & Franks, PJS 2011, 'DEEPWATER HORIZON OIL SPILL A Review of the Planktonic Response', OCEANOGRAPHY, vol. 24, no. 3, pp. 294-301.
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Ajani, PA, Ingleton, T, Pritchard, T & Armand, L 2011, 'Microalgal Blooms in the Coastal Waters of New South Wales, Australia.', Linnean Society of New South Wales. Proceedings (Online), vol. 133, pp. 15-32.
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Baird, ME, Suthers, I, Griffin, DA, Hollings, B, Pattiaratchi, CB, Everett, J, Roughan, M, Oubelkheir, K & Doblin, MA 2011, 'The effect of surface flooding on the physical-biogeochemical dynamics of a warm-core eddy off southeast Australia', Deep Sea Research Part II: Topical Studies in Oceanography, vol. 58, no. 5, pp. 592-605.
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Warm core eddies (WCEs) formed from the East Australian Current (EAC) play an important role in the heat, mass and biogeochemical budgets of the western Tasman Sea. The development and separation of an EAC WCE during July-December 2008 was observed using remotely-sensed temperature, ocean colour and sea-level elevation, three Argo floats, a shipboard CTD, a shelf mooring array and a 15-day deployment of a Slocum glider.
Becraft, ED, Cohan, FM, Kuhl, M, Jensen, SO & Ward, DM 2011, 'Fine-Scale Distribution Patterns of Synechococcus Ecological Diversity in Microbial Mats of Mushroom Spring, Yellowstone National Park', Applied and Environmental Microbiology, vol. 77, no. 21, pp. 7689-7697.
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Past analyses of sequence diversity in high-resolution protein-encoding genes have identified putative ecological species of unicellular cyanobacteria in the genus Synechococcus, which are specialized to 60 degrees C but not 65 degrees C in Mushroom Spri
Behrendt, L, Larkum, A, Norman, A, Qvortrup, K, Chen, M, Ralph, PJ, Sorensen, SJ, Trampe, E & Kuhl, M 2011, 'Endolithic chlorophyll d-containing phototrophs', ISME Journal, vol. 5, no. 6, pp. 1072-1076.
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Cyanobacteria in the genus Acaryochloris are the only known oxyphototrophs that have exchanged chlorophyll a (Chl a) with Chl d as their primary photopigment, facilitating oxygenic photosynthesis with near infrared (NIR) light. Yet their ecology and natural habitats are largely unknown. We used hyperspectral and variable chlorophyll fluorescence imaging, scanning electron microscopy, photopigment analysis and DNA sequencing to show that Acaryochloris-like cyanobacteria thrive underneath crustose coralline algae in a widespread endolithic habitat on coral reefs. This finding suggests an important role of Chl d-containing cyanobacteria in a range of hitherto unexplored endolithic habitats, where NIR light-driven oxygenic photosynthesis may be significant.
Ben-Dov, E, Siboni, N, Shapiro, OH, Arotsker, L & Kushmaro, A 2011, 'Substitution by Inosine at the 3 '-Ultimate and Penultimate Positions of 16S rRNA Gene Universal Primers', MICROBIAL ECOLOGY, vol. 61, no. 1, pp. 1-6.
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Brading, P, Warner, ME, Davey, P, Smith, DJ, Achterberg, EP & Suggett, DJ 2011, 'Differential effects of ocean acidification on growth and photosynthesis among phylotypes of Symbiodinium (Dinophyceae)', Limnology And Oceanography, vol. 56, no. 3, pp. 927-938.
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We investigated the effect of elevated partial pressure of CO2 (pCO(2)) on the photosynthesis and growth of four phylotypes (ITS2 types A1, A13, A2, and B1) from the genus Symbiodinium, a diverse dinoflagellate group that is important, both free-living a
Chan, Y-W, Mohr, R, Millard, AD, Holmes, AB, Larkum, AW, Whitworth, AL, Mann, NH, Scanlan, DJ, Hess, WR & Clokie, MRJ 2011, 'Discovery of Cyanophage Genomes Which Contain Mitochondrial DNA Polymerase', MOLECULAR BIOLOGY AND EVOLUTION, vol. 28, no. 8, pp. 2269-2274.
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Cooper, TF, Ulstrup, K, Dandan, SS, Heyward, AJ, Kuhl, M, Muirhead, A, O'Leary, RA, Ziersen, BE & van Oppen, MJ 2011, 'Niche specialization of reef-building corals in the mesophotic zone: metabolic trade-offs between divergent Symbiodinium types', Proceedings Of The Royal Society Of London Series B-biological Sciences, vol. 278, no. 1713, pp. 1840-1850.
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The photobiology of two reef corals and the distribution of associated symbiont types were investigated over a depth gradient of 0-60 m at Scott Reef, Western Australia. Pachyseris speciosa hosted mainly the same Symbiodinium C type similar to C3 irrespective of sampling depth. By contrast, Seriatopora hystrix hosted predominantly Symbiodinium type D1a or D1a-like at shallow depths while those in deeper water were dominated by a Symbiodinium C type closely related to C1. The photosynthesis/respiration (P/R) ratio increased consistently with depth at the two sampling times (November 2008 and April 2009) for P. speciosa and in November 2008 only for S. hystrix, suggesting a reduction in metabolic energy expended for every unit of energy obtained from photosynthesis. However, in April 2009, shallow colonies of S. hystrix exhibited decreased P/R ratios down to depths of approximately 23 m, below which the ratio increased towards the maximum depth sampled. This pattern was mirrored by changes in tissue biomass determined as total protein content. The depth of change in the direction of the P/R ratio correlated with a shift from Symbiodinium D to C-dominated colonies. We conclude that while photobiological flexibility is vital for persistence in contrasting light regimes, a shift in Symbiodinium type may also confer a functional advantage albeit at a metabolic cost with increased depth.
Doblin, MA, Petrou, K, Shelly, K, Westwood, K, van den Enden, R, Wright, S, Griffiths, B & Ralph, PJ 2011, 'Diel variation of chlorophyll-a fluorescence, phytoplankton pigments and productivity in the Sub-Antarctic and Polar Front Zones south of Tasmania, Australia', Deep Sea Research Part II: Topical Studies in Oceanography, vol. 58, no. 21-22, pp. 2189-2199.
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Marine primary production is a fundamental measure of the oceanâs capacity to convert carbon dioxide to particulate organic carbon for the marine foodweb, and as such is an essential variable used in ecosystem and biogeochemical models to assess trophic dynamics and carbon cycling. The Sub-Antarctic Zone (SAZ) is a major sink for atmospheric carbon and exhibits large gradients in ocean conditions on both temporal and spatial scales. In this dynamic system, an understanding of small-scale temporal changes is critical for modelling primary production at larger scales. Thus, we investigated diel effects on maximum quantum yield of PSII (FV/FM), photosynthetic pigment pools and primary productivity in the western (Diel 1) and eastern SAZ region (Diel 3) south of Tasmania, Australia, and compared this to a station at the polar front (Diel 2). Phytoplankton in the eastern SAZ had the greatest diel response, with cells showing decreased FV/FM and increased biosynthesis and transformation of xanthophyll and other photoprotective pigments during the day, but only in the surface waters (0 and 10m). Diel responses diminished by 30 m. Cells in the western SAZ had similar responses across the depths sampled, increasing their FV/FM during the night and increasing their xanthophyll pigment content during the day. Phytoplankton at the polar front (Diel 2) showed intermediate diel-related variations in photophysiology, with xanthophyll conversion and increases in photoprotective pigments during the day but constant FV/FM.
Dongen-Vogels, V, Seymour, JR, Middleton, JF, Mitchell, JG & Seuront, L 2011, 'Influence of local physical events on picophytoplankton spatial and temporal dynamics in South Australian continental shelf waters', Journal of Plankton Research, vol. 33, no. 12, pp. 1825-1841.
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We investigated the space-time dynamics of picophytoplankton in South Australian continental shelf waters from February 2008 to January 2009, focusing on localized physical events. We discriminated six picophytoplankton populations by flow cytometry, including Synechococcus (SYN1, SYN2), Prochlorococcus (PROC1, PROC2) and small and large picoeukaryotes (EUKS, EUKL). Local physical events observed included downwelling and dense waters outflowing from a nearby gulf in winter-early spring 2008, upwelling in summer and early spring 2008 and eddy formation in January 2009. Each population responded differently to these events, which resulted in up to four orders of magnitude changes in their abundances. Population-specific hotspots reflected a succession of distinct dominant communities associated with the strength of upwelling events, changes in fluorescence maximum depths and local downwelling and mixing processes. The unexpected high abundances and local dominance of Prochlorococcus in summer reflected the possible influence of eastward and westward current transports and the presence of a High-Light (PROC1)-and Low-Light (PROC2)-adapted ecotypes. This study highlights the role of localized physical events in the dominance of all three picophytoplankton groups that may be critical for the high productivity of the study region, and suggests the importance of hydroclimatic forcing for inter-annual changes in picophytoplankton communities.
Earp, AA, Hanson, CE, Ralph, PJ, Brando, VE, Allen, S, Baird, ME, Clementson, L, Daniel, P, Dekker, AG, Fearns, PR, Parslow, JS, Strutton, PG, Thompson, P, Underwood, M, Weeks, S & Doblin, MA 2011, 'Review of fluorescent standards for calibration of in situ fluorometers: Recommendations applied in coastal and ocean observing programs', Optics Express, vol. 19, no. 27, pp. 26768-26782.
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Fluorometers are widely used in ecosystem observing to monitor fluorescence signals from organic compounds, as well as to infer geophysical parameters such as chlorophyll or CDOM concentration, but measurements are susceptible to variation caused by biofouling, instrument design, sensor drift, operating environment, and calibration rigor. To collect high quality data, such sensors need frequent checking and regular calibration. In this study, a wide variety of both liquid and solid fluorescent materials were trialed to assess their suitability as reference standards for performance assessment of in situ fluorometers. Criteria used to evaluate the standards included the spectral excitation/emission responses of the materials relative to fluorescence sensors and to targeted ocean properties, the linearity of the fluorometerâs optical response with increasing concentration, stability and consistency, availability and ease of use, as well as cost. Findings are summarized as a series of recommended reference standards for sensors deployed on stationary and mobile platforms, to suit a variety of in situ coastal to ocean sensor configurations. Repeated determinations of chlorophyll scale factor using the recommended liquid standard, Fluorescein, achieved an accuracy of 2.5%. Repeated measurements with the recommended solid standard, Plexiglas Satinice® plum 4H01 DC (polymethylmethacrylate), over an 18 day period varied from the mean value by 1.0% for chlorophyll sensors and 3.3% for CDOM sensors.
Elberling, B, Askaer, L, Jørgensen, CJ, Joensen, HP, Kuhl, M, Glud, RN & Lauritsen, FR 2011, 'Linking soil O2, CO2, and CH4 concentrations in a wetland soil: Implications for CO2 and CH4 fluxes', Environmental Science & Technology, vol. 45, no. 8, pp. 3393-3399.
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Oxygen (O2) availability and diffusivity in wetlands are controlling factors for the production and consumption of both carbon dioxide (CO2) and methane (CH4) in the subsoil and thereby potential emission of these greenhouse gases to the atmosphere. To examine the linkage between highresolution spatiotemporal trends in O2 availability and CH4/CO2 dynamics in situ, we compare high-resolution subsurface O2 concentrations, weekly measurements of subsurface CH4/CO2 concentrations and near continuous flux measurements of CO2 and CH4. Detailed 2-D distributions of O2 concentrations and depth-profiles of CO2 and CH4 were measured in the laboratory during flooding of soil columns using a combination of planar O2 optodes and membrane inlet mass spectrometry. Microsensors were used to assess apparent diffusivity under both field and laboratory conditions. Gas concentration profiles were analyzed with a diffusion-reaction model for quantifying production/ consumption profiles of O2, CO2, and CH4. In drained conditions, O2 consumption exceeded CO2 production, indicating CO2 dissolution in the remaining water-filled pockets. CH4 emissions were negligible when the oxic zone was >40 cm and CH4 was presumably consumed below the depth of detectable O2. In flooded conditions, O2 was transported by other mechanisms than simple diffusion in the aqueous phase. This work demonstrates the importance of changes in near-surface apparent diffusivity, microscale O2 dynamics, as well as gas transport via aerenchymous plants tissue on soil gas dynamics and greenhouse gas emissions following marked changes in water level.
Fleishman, SJ, Leaver-Fay, A, Corn, JE, Strauch, E-M, Khare, SD, Koga, N, Ashworth, J, Murphy, P, Richter, F, Lemmon, G, Meiler, J & Baker, D 2011, 'RosettaScripts: A Scripting Language Interface to the Rosetta Macromolecular Modeling Suite', PLOS ONE, vol. 6, no. 6.
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Gupta, V, Baghel, RS, Kumar, M, Kumari, P, Mantri, VA, Reddy, CRK & Jha, B 2011, 'Growth and agarose characteristics of isomorphic gametophyte (male and female) and sporophyte of Gracilaria dura and their marker assisted selection', AQUACULTURE, vol. 318, no. 3-4, pp. 389-396.
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Gupta, V, Kumar, M, Brahmbhatt, H, Reddy, CRK, Seth, A & Jha, B 2011, 'Simultaneous determination of different endogenetic plant growth regulators in common green seaweeds using dispersive liquid-liquid microextraction method', PLANT PHYSIOLOGY AND BIOCHEMISTRY, vol. 49, no. 11, pp. 1259-1263.
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Gupta, V, Kumar, M, Kumari, P, Reddy, CRK & Jha, B 2011, 'Optimization of protoplast yields from the red algae Gracilaria dura (C. Agardh) J. Agardh and G. verrucosa (Huds.) Papenfuss', JOURNAL OF APPLIED PHYCOLOGY, vol. 23, no. 2, pp. 209-218.
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Hansen, MO, Buchardt, B, Kuhl, M & Elberling, B 2011, 'The fate of the submarine Ikaite Tufa columns in Southwest Greenland under changing climate conditions', Journal Of Sedimentary Research, vol. 81, no. 7-8, pp. 553-561.
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Ikaite is considered a metastable mineral forming and stable only at low temperatures and therefore an indicator of low-temperature carbonate precipitation often associated with cold marine seeps. It is found world-wide but most spectacularly in Ikka Fjord in southwest Greenland as submarine carbonate tufa columns. Here, ikaite is formed as a result of submarine spring water mixing with cold seawater. As ikaite disintegrates at temperatures above 6-7C, it has been speculated that global warming could endanger this unique habitat as well as other sites. In Ikka Fjord in situ water chemistry in and around an ikaite column measured continuously over two years showed that the column water is alkaline (pH >9-10) throughout the year with temperatures of -1.3-6.0C and conductivities of 5.7-7.9 mS cm(-1), favoring year-round growth of columns at 4-5 cm per month. Short-term in situ measurements with needle micro sensors from both older dehydrated and calcified parts and more recently formed solid parts of an ikaite tufa column showed similar pH and temperature values, including a temperature variation over the tidal cycle. In the uppermost, recently deposited ikaite matrix, spring water escaping at the top causes passive drag of seawater into the porous ikaite matrix, leading to a mixing layer several centimeters thick that has pH values intermediate to the spring water in the column and the surrounding seawater. We conclude that the main part of the columns, consisting of fossilized ikaite (inverted to calcite) partly sealed by calcifying coralline algae and with year-round flow of alkaline freshwater through distinct channels, are resistant to warming. In the more diffuse top part of the columns, the formation of ikaite, and thus column growth, will be limited in the future due to increased fjord water temperature during the <3 summer months a year.
Hassler, CS, Djajadikarta, J, Doblin, MA, Everett, J & Thompson, P 2011, 'Characterisation Of Water Masses And Phytoplankton Nutrient Limitation In The East Australian Current Separation Zone During Spring 2008', Deep Sea Research Part II: Topical Studies in Oceanography, vol. 58, no. 5, pp. 664-677.
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This study focuses on the comparison of oceanic and coastal cold-core eddies with inner-shelf and East Australian Current (EAC) waters at the time of the spring bloom (October 2008).
Hill, R, Brown, CM, DeZeeuw, K, Campbell, DA & Ralph, PJ 2011, 'Increased rate of D1 repair in coral symbionts during bleaching is insufficient to counter accelerated photo-inactivation', Limnology and Oceanography, vol. 56, no. 1, pp. 139-146.
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We dissect the primary photo-inactivation and the counteracting metabolic repair rates in fragments of the scleractinian coral, Pocillopora damicornis, subjected to a combined stress of a shift to elevated temperature (from 26 degrees C to 32 degrees C) and increased light (from 200 mu mol photons m(-2) s(-1) to 400 mmol photons m(-2) s(-1)) to induce bleaching. During the bleaching treatment the dinoflagellate symbionts showed a 5.5-fold acceleration in their photosystem II (PSII) repair rate constant, demonstrating that they maintain strong metabolic capacity to clear and replace photo-damaged D1 protein at the elevated temperature and light conditions. Nevertheless, the symbionts concurrently suffered a seven-fold increase in the rate constant for PSII photo-inactivation. This rapid photo-inactivation exceeded the PSII repair capacity, therefore tipping the symbionts, and by implication the symbiosis, into net photo-inhibition. Increased photo-inactivation in hospite, rather than an inhibition of PSII repair, is the principle trigger for net photo-inhibition under bleaching conditions.
Hoeksema, BW & Matthews, JL 2011, 'Contrasting bleaching patterns in mushroom coral assemblages at Koh Tao, Gulf of Thailand', CORAL REEFS, vol. 30, no. 1, pp. 95-95.
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Jeffries, TC, Seymour, JR, Gilbert, JA, Dinsdale, EA, Newton, K, Leterme, SS, Roudnew, B, Smith, RJ, Seuront, L & Mitchell, JG 2011, 'Substrate type determines metagenomic profiles from diverse chemical habitats', PLoS One, vol. 6, no. 9, pp. 1-9.
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Environmental parameters drive phenotypic and genotypic frequency variations in microbial communities and thus control the extent and structure of microbial diversity. We tested the extent to which microbial community composition changes are controlled by shifting physiochemical properties within a hypersaline lagoon. We sequenced four sediment metagenomes from the Coorong, South Australia from samples which varied in salinity by 99 Practical Salinity Units (PSU), an order of magnitude in ammonia concentration and two orders of magnitude in microbial abundance. Despite the marked divergence in environmental parameters observed between samples, hierarchical clustering of taxonomic and metabolic profiles of these metagenomes showed striking similarity between the samples (>89%). Comparison of these profiles to those derived from a wide variety of publically available datasets demonstrated that the Coorong sediment metagenomes were similar to other sediment, soil, biofilm and microbial mat samples regardless of salinity (>85% similarity). Overall, clustering of solid substrate and water metagenomes into discrete similarity groups based on functional potential indicated that the dichotomy between water and solid matrices is a fundamental determinant of community microbial metabolism that is not masked by salinity, nutrient concentration or microbial abundance.
Jensen, SI, Steunou, A, Bhaya, D, Kuhl, M & Grossman, AR 2011, 'In situ dynamics of O2, pH and cyanobacterial transcripts associated with CCM, photosynthesis and detoxification of ROS', ISME Journal, vol. 5, no. 2, pp. 317-328.
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The relative abundance of transcripts encoding proteins involved in inorganic carbon concentrating mechanisms (CCM), detoxification of reactive oxygen species (ROS) and photosynthesis in the thermophilic cyanobacterium Synechococcus OS-B0 was measured in hot spring microbial mats over two diel cycles, and was coupled with in situ determinations of incoming irradiance and microenvironmental dynamics of O2 and pH. Fluctuations in pH and O2 in the mats were largely driven by the diel cycle of solar irradiance, with a pH variation from B7.0 to B9.5, and O2 levels ranging from anoxia to supersaturation during night and day, respectively. Levels of various transcripts from mat cyanobacteria revealed several patterns that correlated with incident irradiance, O2 and pH within the mat matrix. Transcript abundances for most genes increased during the morning darkâlight transition. Some transcripts remained at a near constant level throughout the light period, whereas others showed an additional increase in abundance as the mat underwent transition from low-to-high light (potentially reflecting changes in O2 concentration and pH), followed by either a decreased abundance in the early afternoon, or a gradual decline during the early afternoon and into the evening. One specific transcipt, psbA1, was the lowest during mid-day under high irradiance and increased when the light levels declined. We discuss these complex in situ transcriptional patterns with respect to environmental and endogenous cues that might impact and regulate transcription over the diel cycle.
Jimenez Denness, IM, Kuhl, M, Larkum, A & Ralph, PJ 2011, 'Effects of flow and colony morphology on the thermal boundary layer of corals', Journal of the Royal Society Interface, vol. 8, no. 65, pp. 1785-1795.
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The thermal microenvironment of corals and the thermal effects of changing flow and radiation are critical to understanding heat-induced coral bleaching, a stress response resulting from the destruction of the symbiosis between corals and their photosynt
Kaniewska, P, Magnusson, SH, Anthony, KR, Reef, R, Kuhl, M & Hoegh-Guldberg, O 2011, 'Importance Of Macro- Versus Microstructure In Modulating Light Levels Inside Coral Colonies', Journal of Phycology, vol. 47, no. 4, pp. 846-860.
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Adjusting the light exposure and capture of their symbiotic photosynthetic dinoflagellates (genus Symbiodinium Freud.) is central to the success of reef-building corals (order Scleractinia) across high spatio-temporal variation in the light environment of coral reefs. We tested the hypothesis that optical properties of tissues in some coral species can provide light management at the tissue scale comparable to light modulation by colony architecture in other species. We compared within-tissue scalar irradiance in two coral species from the same light habitat but with contrasting colony growth forms: branching Stylophora pistillata and massive Lobophyllia corymbosa. Scalar irradiance at the level of the symbionts (2 mm into the coral tissues) were <10% of ambient irradiance and nearly identical for the two species, despite substantially different light environments at the tissue surface. In S. pistillata, light attenuation (90% relative to ambient) was observed predominantly at the colony level as a result of branch-to-branch self-shading, while in L. corymbosa, near-complete light attenuation (97% relative to ambient) was occurring due to tissue optical properties. The latter could be explained partly by differences in photosynthetic pigment content in the symbiont cells and pigmentation in the coral host tissue. Our results demonstrate that different strategies of light modulation at colony, polyp, and cellular levels by contrasting morphologies are equally effective in achieving favorable irradiances at the level of coral photosymbionts.
Kerrison, P, Hall-Spencer, JM, Suggett, DJ, Hepburn, LJ & Steinke, M 2011, 'Assessment of pH variability at a coastal CO2 vent for ocean acidification studies', Estuarine Coastal And Shelf Science, vol. 94, no. 2, pp. 129-137.
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Marine environments with naturally high CO2 concentrations have become important research sites for studying the impacts of future ocean acidification on biological processes. We conducted high temporal resolution pH and temperature measurements in and around a shallow (2.5-3 m) CO2 vent site off Ischia, Italy in May and June 2008. Loggers were deployed at five stations to monitor water at both the surface and benthos. Our reference station, 500 m from the CO2 vent, had no noticeable vent influence. It had a naturally high and stable benthic pH (mean 8.16, inter-quartile range (IQ): 8.14-8.18) fluctuating with diel periodicity, presumably driven by community photosynthesis and respiration. A principal component analysis (PCA) revealed that the pH of this station was well constrained by meteorological parameters. In contrast, a station positioned within the vent zone, had a low and very variable benthic mean pH of 7.11 (IQ: 6.91-7.62) with large pH fluctuations not well constrained by a PCA. Any stations positioned within 20 m of the main vent zone had lowered pH, but suffered from abnormally large pH fluctuations making them unsuitable representatives to predict future changes to a shallow coastal environment. Between these extremes, we identified a benthic area with a lower pH of 7.84 (IQ: 7.83-7.88) that retained many of the characteristics of the reference station such as a natural diel pH periodicity and low variability. Our results indicate that a range of pH environments maybe commonplace near CO2 vents due to their characteristic acidification of benthic water over a wide area. Such environments could become invaluable natural laboratories for ocean acidification research, closely mimicking future CO2 conditions in a natural setting
Khan, N-UH, Pandya, N, Maity, NC, Kumar, M, Patel, RM, Kureshy, RI, Abdi, SHR, Mishra, S, Das, S & Bajaj, HC 2011, 'Influence of chirality of V(V) Schiff base complexes on DNA, BSA binding and cleavage activity', EUROPEAN JOURNAL OF MEDICINAL CHEMISTRY, vol. 46, no. 10, pp. 5074-5085.
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Kirchhoff, H, Hall, C, Wood, M, Herbstová, M, Tsabari, O, Nevo, R, Charuvi, D, Shimoni, E & Reich, Z 2011, 'Dynamic control of protein diffusion within the granal thylakoid lumen', Proceedings of the National Academy of Sciences of the United States of America, vol. 108, no. 50, pp. 20248-20253.
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The machinery that conducts the light-driven reactions of oxygenic photosynthesis is hosted within specialized paired membranes called thylakoids. In higher plants, the thylakoids are segregated into two morphological and functional domains called grana and stroma lamellae. A large fraction of the luminal volume of the granal thylakoids is occupied by the oxygen-evolving complex of photosystem II. Electron microscopy data we obtained on dark- and light-adapted Arabidopsis thylakoids indicate that the granal thylakoid lumen significantly expands in the light. Models generated for the organization of the oxygen-evolving complex within the granal lumen predict that the light-induced expansion greatly alleviates restrictions imposed on protein diffusion in this compartment in the dark. Experiments monitoring the redox kinetics of the luminal electron carrier plastocyanin support this prediction. The impact of the increase in protein mobility within the granal luminal compartment in the light on photosynthetic electron transport rates and processes associated with the repair of photodamaged photosystem II complexes is discussed.
Klatt, CG, Wood, JM, Rusch, DB, Bateson, MM, Hamamura, N, Heidelberg, JF, Grossman, AR, Bhaya, D, Cohan, FM, Kuhl, M, Bryant, DA & Ward, DM 2011, 'Community ecology of hot spring cyanobacterial mats: predominant populations and their functional potential', ISME Journal, vol. 5, no. 8, pp. 1262-1278.
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Phototrophic microbial mat communities from 60 1C and 65 1C regions in the effluent channels of Mushroom and Octopus Springs (Yellowstone National Park, WY, USA) were investigated by shotgun metagenomic sequencing. Analyses of assembled metagenomic sequences resolved six dominant chlorophototrophic populations and permitted the discovery and characterization of undescribed but predominant community members and their physiological potential. Linkage of phylogenetic marker genes and functional genes showed novel chlorophototrophic bacteria belonging to uncharacterized lineages within the order Chlorobiales and within the Kingdom Chloroflexi. The latter is the first chlorophototrophic member of Kingdom Chloroflexi that lies outside the monophyletic group of chlorophototrophs of the Order Chloroflexales. Direct comparison of unassembled metagenomic sequences to genomes of representative isolates showed extensive genetic diversity, genomic rearrangements and novel physiological potential in native populations as compared with genomic references. Synechococcus spp. metagenomic sequences showed a high degree of synteny with the reference genomes of Synechococcus spp. strains A and B0, but synteny declined with decreasing sequence relatedness to these references. There was evidence of horizontal gene transfer among native populations, but the frequency of these events was inversely proportional to phylogenetic relatedness.
Kolpen, M, Kuhl, M, Bjarnsholt, T, Moser, C, Hansen, CR, Moller, LL, Pressler, T, Hoiby, N & Jensen, P 2011, 'N2O PRODUCTION IN SPUTUM FROM CHRONICALLY INFECTED CYSTIC FIBROSIS PATIENTS', PEDIATRIC PULMONOLOGY, pp. 316-316.
Kuhl, M 2011, 'New insights into Mediterranean cold seep ecosystems: editorial comment on the feature article by Ritt et al', Marine Biology, vol. 158, no. 6, pp. 1185-1185.
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Tectonically active areas of the ocean Xoor harbor diverse benthic ecosystems that are essentially independent of photosynthesis and are largely driven by chemosynthetic bacterial processes. This includes symbiotic relationships between invertebrates and chemosynthetic bacteria oxidizing, e.g., methane (CH4) or sulWde (H2S). In contrast to the relatively ephemeral hydrothermal vent systems that Xourish along very active rift zones and other hot spots of volcanic activity, cold seeps are more long-term stable systems found in less active areas around Wssure zones in the sea Xoor, where reduced gases (H2S, CH4) and hydrocarbonrich Xuids emerge over larger areas (Levin 2005).
Kumar, M, Gupta, V, Trivedi, N, Kumari, P, Bijo, AJ, Reddy, CRK & Jha, B 2011, 'Desiccation induced oxidative stress and its biochemical responses in intertidal red alga Gracilaria corticata (Gracilariales, Rhodophyta)', ENVIRONMENTAL AND EXPERIMENTAL BOTANY, vol. 72, no. 2, pp. 194-201.
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Kumar, M, Kumari, P, Trivedi, N, Shukla, MK, Gupta, V, Reddy, CRK & Jha, B 2011, 'Minerals, PUFAs and antioxidant properties of some tropical seaweed from Saurashtra coast of India', Journal of Applied Phycology, vol. 23, no. 5, pp. 797-810.
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Abstract
Twenty-two tropical seaweeds from the Rhodophyta, Phaeophyta and Chlorophyta were examined for their possible use as nutritional supplements. All seaweeds contained balanced Na/K and C/N ratio and high amounts of macroelements (Na, K, Ca, and Mg) as compared to the terrestrial vegetables. Among the microelements, Fe was the highest followed by Zn, Mn, Cu and other trace elements. Fatty acid distribution showed high level of n-6 and n-3 polyunsaturated fatty acids (PUFAs), and their ratios were within the WHO prescribed limits. The higher ratios of PUFA/SFA (>0.4) are in agreement with the recommendations of nutritional guidelines. Most of the species, especially the Chlorophyta and Phaeophyta, had permissible intake values of unsaturation, atherogenic and thrombogenic indexes comparable to milk-based products. Principal component analysis demonstrated a correlation between total phenolic content, total antioxidant activity, DPPH, and O 2 •− radical scavenging activity, suggesting polyphenols as the chief contributor to the antioxidant activity in seaweeds. These results indicate that these seaweeds could be a potential source of natural antioxidants, minerals and high-quality PUFAs and may be efficiently used as ingredients in functional foods.
Kumar, M, Trivedi, N, Reddy, CRK & Jha, B 2011, 'Toxic Effects of Imidazolium Ionic Liquids on the Green Seaweed Ulva lactuca: Oxidative Stress and DNA Damage', CHEMICAL RESEARCH IN TOXICOLOGY, vol. 24, no. 11, pp. 1882-1890.
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Larkum, A, Salih, A & Kuhl, M 2011, 'Rapid Mass Movement of Chloroplasts during Segment Formation of the Calcifying Siphonalean Green Alga, Halimeda macroloba', PLoS One, vol. 6, no. 7, pp. 1-9.
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Background: The calcifying siphonalean green alga, Halimeda macroloba is abundant on coral reefs and is important in the production of calcium carbonate sediments. The process by which new green segments are formed over-night is revealed here for the first time. Methodology/Principal Findings: Growth of new segments was visualised by epifluorescence and confocal microscopy and by pulse amplitude modulation (PAM) fluorimetry. Apical colourless proto-segments were initiated on day 1, and formed a loose network of non-calcified, non-septate filaments, containing no chloroplasts. Rapid greening was initiated at dusk by i) the mass movement of chloroplasts into these filaments from the parent segment and ii) the growth of new filaments containing chloroplasts. Greening was usually complete in 3-5 h and certainly before dawn on day 2 when the first signs of calcification were apparent. Mass chloroplast movement took place at a rate of 0.65 mm/s. Photosynthetic yield and rate remained low for a period of 1 to several hours, indicating that the chloroplasts were made de novo. Use of the inhibitors colchicine and cytochalasin d indicated that the movement process is dependent on both microtubules and microfilaments. Significance: This unusual process involves the mass movement of chloroplasts at a high rate into new segments during the night and rapid calcification on the following day and may be an adaptation to minimise the impact of herbivorous activity.
Liengaard, L, Nielsen, LP, Revsbech, NP, Elberling, B, Prieme, A, Prast, A & Kuhl, M 2011, 'Effects Of Flooding Cycles In The Pantanal On The Turnover Of Soil Nitrogen Pools And Emission Of N2O', Biogeosciences Discussion, vol. 8, no. 3, pp. 5991-6030.
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The global nitrous oxide (N2O) budget remains unbalanced. Currently, ~25 % of the global N2O emission is ascribed to uncultivated tropical soils, but the exact locations and controlling mechanisms are not clear. In this study, we present the first detailed study of the dynamics of soil nitrogen pools and flux of N2O from the world's largest wetland Pantanal, South America. At three long-term measurement sites we measured porewater pH, NO3, NH4+ , N2O and O2 as well as N2O dynamics in soil slurry, and in situ fluxes of N2O and CO2. The pool of inorganic nitrogen changed (7.192 µg NH4+-N g dw-1, and 0.1201 µg NO3-N g dw1) with the seasonal flooding and drying cycles, indicating dynamic shifts between ammonification, nitrification and denitrification. In the field, O2 penetrated to a depth of 60 cm in dry soil, but O2 was rapidly depleted in response to precipitation. Soil pH fluctuated from pH 77.5 in flooded soil to pH 3.54.5 in the same drained soil. Microsensor measurements showed rapid N2O accumulation reaching >5001000 Pa in soil slurries due to incomplete denitrification. In situ fluxes of N2O were comparable to heavily fertilized forest or agricultural soils. The dominating parameter affecting N2O emission rate was precipitation inducing peak emissions of >3 mmol N2O m-2 d-1, while the mean daily flux was 0.43 mmol N2O m-2 d-1. Single measurement based screening of in situ activity at 10 Pantanal sites during dry conditions averaged 0.39 mmol N2O m-2 d-1
Mai, K, Smith, NC, Feng, Z, Katrib, M, Slapeta, J, Slapetova, I, Wallach, M, Luxford, C, Davies, MJ, Zhang, X, Norton, RS & Belli, SI 2011, 'Peroxidase catalysed cross-linking of an intrinsically unstructured protein via dityrosine bonds in the oocyst wall of the apicomplexan parasite, Eimeria maxima', International Journal For Parasitology, vol. 41, no. 11, pp. 1157-1164.
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Apicomplexan parasites such as Eimeria maxima possess a resilient oocyst wall that protects them upon excretion in host faeces and in the outside world, allowing them to survive between hosts. The wall is formed from the contents of specialised organelles - wall-forming bodies - found in macrogametes of the parasites. The presence of dityrosine in the oocyst wall suggests that peroxidase-catalysed dityrosine cross-linking of tyrosine-rich proteins from wall-forming bodies forms a matrix that is a crucial component of oocyst walls. Bioinformatic analyses showed that one of these tyrosine-rich proteins, EmGAM56, is an intrinsically unstructured protein, dominated by random coil (52-70%), with some alpha-helix (28-43%) but a relatively low percentage of beta-sheet (1-11%); this was confirmed by nuclear magnetic resonance and circular dichroism. Furthermore, the structural integrity of EmGAM56 under extreme temperatures and pH indicated its disordered nature. The intrinsic lack of structure in EmGAM56 could facilitate its incorporation into the oocyst wall in two ways: first, intrinsically unstructured proteins are highly susceptible to proteolysis, explaining the several differently-sized oocyst wall proteins derived from EmGAM56; and, second, its flexibility could facilitate cross-linking between these tyrosine-rich derivatives. An in vitro cross-linking assay was developed using a recombinant 42 kDa truncation of EmGAM56. Peroxides, in combination with plant or fungal peroxidases, catalysed the rapid formation of dityrosine cross-linked polymers of the truncated EmGAM56, as determined by western blotting and HPLC, confirming this protein's propensity to form dityrosine bonds.
Marcos, M, Seymour, JR, Luhar, M, Mitchell, JG, Durham, WM, Macke, A & Stocker, R 2011, 'Microbial Alignment In Flow Changes Ocean Light Climate', Proceedings Of The National Academy Of Sciences Of The United States Of America, vol. 108, no. 10, pp. 3860-3864.
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The growth of microbial cultures in the laboratory often is assessed informally with a quick flick of the wrist: dense suspensions of microorganisms produce translucent
Mella-Flores, D, Mazard, S, Humily, F, Partensky, F, Mahe, F, Bariat, L, Courties, C, Marie, D, Ras, J, Mauriac, R, Jeanthon, C, Bendif, EM, Ostrowski, M, Scanlan, DJ & Garczarek, L 2011, 'Is the distribution of Prochlorococcus and Synechococcus ecotypes in the Mediterranean Sea affected by global warming?', BIOGEOSCIENCES, vol. 8, no. 9, pp. 2785-2804.
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Munro, TP, Mahler, SM, Huang, EP, Chin, DY & Gray, PP 2011, 'Bridging the gap', mAbs, vol. 3, no. 5, pp. 440-452.
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Murray, SA, Mihali, TK & Neilan, BA 2011, 'Extraordinary conservation, gene loss, and positive selection in the evolution of an ancient neurotoxin', Molecular Biology And Evolution, vol. 28, no. 3, pp. 1173-1182.
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The recent determination of the genetic basis for the biosynthesis of the neurotoxin, saxitoxin, produced by cyanobacteria, has revealed a highly complex sequence of reactions, involving over 30 biosynthetic steps encoded by up to 26 genes clustered at o
Murray, SA, Wiese, M, Stuken, A, Brett, S, Kellmann, R, Hallegraeff, G & Neilan, BA 2011, 'A quantitative molecular assay based on the gene sxtA to identify saxitoxin-producing harmful algal blooms in marine waters', Applied and Environmental Microbiology, vol. 77, no. 19, pp. 7050-7057.
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The recent identification of genes involved in the production of the potent neurotoxin and keystone metabolite saxitoxin (STX) in marine eukaryotic phytoplankton has allowed us for the first time to develop molecular genetic methods to investigate the ch
Nagahama, Y, Murray, SA, Tomaru, A & Fukuyo, Y 2011, 'Species boundaries in the toxic dinoflagellate Prorocentrum lima (Dinophyceae, Prorocentrales), based on morphological and phylogenetic characters', Journal of Phycology, vol. 47, no. 1, pp. 178-189.
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Wild and cultured specimens of Prorocentrum lima (Ehrenb.) F. Stein from 26 widely different areas in 13 countries were examined in order to determine consistent characters for delimiting species boundaries in this taxon. The morphological characters val
Nagy, G, Posselt, D, Kovacs, L, Holm, JK, Szabo, M, Ughy, B, Rosta, L, Peters, J, Timmins, P & Garab, G 2011, 'Reversible membrane reorganizations during photosynthesis in vivo: revealed by small-angle neutron scattering', Biochemical Journal, vol. 436, pp. 225-230.
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In the present study, we determined characteristic repeat distances of the photosynthetic membranes in living cyanobacterial and eukaryotic algal cells, and in intact thylakoid membranes isolated from higher plants with time-resolved small-angle neutron scattering. This non-invasive technique reveals light-induced reversible reorganizations in the seconds-to-minutes time scale, which appear to be associated with functional changes in vivo.
Pernice, M, Dunn, SR, Miard, T, Dufour, S, Dove, S & Hoegh-Guldberg, O 2011, 'Regulation of Apoptotic Mediators Reveals Dynamic Responses to Thermal Stress in the Reef Building Coral Acropora millepora', PLOS ONE, vol. 6, no. 1.
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Petrou, K & Ralph, PJ 2011, 'Photosynthesis and net primary productivity in three Antarctic diatoms: possible significance for their distribution in the Antarctic marine ecosystem', Marine Ecology Progress Series, vol. 437, pp. 27-40.
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Photosynthesis and net primary productivity were measured in 3 Antarctic diatoms, Fragilariopsis cylindrus, Pseudo-nitzschia subcurvata and Chaetoceros sp., exposed to rapid changes in temperature and salinity representing a range of conditions found during a seasonal cycle. Measured differences in fluorescence-derived photosynthetic activity and oxygen evolution suggested that some alternative electron cycling activity was present under high irradiances. F. cylindrus displayed the highest rates of relative electron transport and net primary productivity under all salinity and temperature combinations and showed adaptive traits towards the sea-ice-like environment. P. subcurvata displayed a preference for low saline conditions where production rates were greatest. However, there was evidence of photosynthetic sensitivity to the lowest temperatures and highest salinities, suggesting a lack of adaptation for dealing with sea-ice-like conditions. Chaetoceros sp. showed high plasticity, acclimating well to all conditions but performing best under pelagic conditions. The study shows species-specific sensitivities to environmental change, highlighting photosynthetic capacity as a potentially important mechanism in ecological niche adaptation. When these data were modelled over different seasons, integrated daily net primary production was greatest under summer pelagic conditions. The findings from this study support the general observations of light control and seasonal development of net primary productivity and species succession in the Antarctic marine ecosystem.
Petrou, K, Doblin, MA & Ralph, PJ 2011, 'Heterogeneity in the photoprotective capacity of three Antarctic diatoms during short-term changes in salinity and temperature', Marine Biology, vol. 158, no. 5, pp. 1029-1041.
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The Antarctic marine ecosystem changes seasonally, forming a temporal continuum of specialised niche habitats including open ocean, sea ice and meltwater environments. The ability for phytoplankton to acclimate rapidly to the changed conditions of these environments depends on the speciesâ physiology and photosynthetic plasticity and may ultimately determine their long-term ecological niche adaptation. This study investigated the photophysiological plasticity and rapid acclimation response of three Antarctic diatomsâFragilariopsis cylindrus, Pseudo-nitzschia subcurvata and Chaetoceros sp.âto a selected range of temperatures and salinities representative of the sea ice, meltwater and pelagic habitats in the Antarctic. Fragilariopsis cylindrus displayed physiological traits typical of adaptation to the sea ice environment. Equally, this species showed photosynthetic plasticity, acclimating to the range of environmental conditions, explaining the prevalence of this species in all Antarctic habitats. Pseudo-nitzschia subcurvata displayed a preference for the meltwater environment, but unlike F. cylindrus, photoprotective capacity was low and regulated via changes in PSII antenna size. Chaetoceros sp. had high plasticity in non-photochemical quenching, suggesting adaptation to variable light conditions experienced in the wind-mixed pelagic environment. While only capturing short-term responses, this study highlights the diversity in photoprotective capacity that exists amongst three dominant Antarctic diatom species and provides insight into links between ecological niche adaptation and speciesâ distribution
Petrou, K, Hassler, CS, Doblin, MA, Shelly, K, Schoemann, V, van den Enden, R, Wright, S & Ralph, PJ 2011, 'Iron-limitation and high light stress on phytoplankton populations from the Australian Sub-Antarctic Zone (SAZ)', Deep Sea Research Part II: Topical Studies in Oceanography, vol. 58, no. 21-22, pp. 2200-2211.
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The high nutrient low chlorophyll (HNLC) surface waters of the Southern Ocean are characterised by high concentrations of nitrate and phosphate, low concentrations of dissolved iron and deep vertical mixing. Future climate scenarios predict increased sur
Petrou, K, Hill, R, Doblin, MA, McMinn, A, Johnson, R, Wright, SW & Ralph, PJ 2011, 'Photoprotection of sea-ice microalgal communities from the east Antarctic pack ice', Journal of Phycology, vol. 47, no. 1, pp. 77-86.
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All photosynthetic organisms endeavor to balance energy supply with demand. For sea-ice diatoms, as with all marine photoautotrophs, light is the most important factor for determining growth and carbonfixation rates. Light varies from extremely low to often relatively high irradiances within the sea-ice environment, meaning that sea-ice algae require moderate physiological plasticity that is necessary for rapid light acclimation and photoprotection. This study investigated photoprotective mechanisms employed by bottom Antarctic sea-ice algae in response to relatively high irradiances to understand how they acclimate to the environmental conditions presented during early spring, as the light climate begins to intensify and snow and sea-ice thinning commences.
Ponton, F, Chapuis, M-P, Pernice, M, Sword, GA & Simpson, SJ 2011, 'Evaluation of potential reference genes for reverse transcription-qPCR studies of physiological responses in Drosophila melanogaster', JOURNAL OF INSECT PHYSIOLOGY, vol. 57, no. 6, pp. 840-850.
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Raghu, AV, Unnikrishnan, K, Geetha, SP, Martin, G & Balachandran, I 2011, 'Plant regeneration and production of embelin from organogenic and embryogenic callus cultures of Embelia ribes Burm. f.-a vulnerable medicinal plant', IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY-PLANT, vol. 47, no. 4, pp. 506-515.
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Rosic, NN, Pernice, M, Dove, S, Dunn, S & Hoegh-Guldberg, O 2011, 'Gene expression profiles of cytosolic heat shock proteins Hsp70 and Hsp90 from symbiotic dinoflagellates in response to thermal stress: possible implications for coral bleaching', CELL STRESS & CHAPERONES, vol. 16, no. 1, pp. 69-80.
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Rosic, NN, Pernice, M, Rodriguez-Lanetty, M & Hoegh-Guldberg, O 2011, 'Validation of Housekeeping Genes for Gene Expression Studies in Symbiodinium Exposed to Thermal and Light Stress', MARINE BIOTECHNOLOGY, vol. 13, no. 3, pp. 355-365.
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Safranek, D, Cerveny, J, Klement, M, Pospisilova, J, Brim, L, Lazar, D & Nedbal, L 2011, 'E-photosynthesis: Web-based platform for modeling of complex photosynthetic processes', BIOSYSTEMS, vol. 103, no. 2, pp. 115-124.
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Shukla, MK, Kumar, M, Prasad, K, Reddy, CRK & Jha, B 2011, 'Partial characterization of sulfohydrolase from Gracilaria dura and evaluation of its potential application in improvement of the agar quality', CARBOHYDRATE POLYMERS, vol. 85, no. 1, pp. 157-163.
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Singh, RP, Gupta, V, Kumari, P, Kumar, M, Reddy, CRK, Prasad, K & Jha, B 2011, 'Purification and partial characterization of an extracellular alginate lyase from Aspergillus oryzae isolated from brown seaweed', JOURNAL OF APPLIED PHYCOLOGY, vol. 23, no. 4, pp. 755-762.
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Sinutok, S, Hill, R, Doblin, MA, Wuhrer, R & Ralph, PJ 2011, 'Warmer more acidic conditions cause decreased productivity and calcification in subtropical coral reef sediment-dwelling calcifiers', Limnology and Oceanography, vol. 56, no. 4, pp. 1200-1212.
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The effects of elevated CO(2) and temperature on photosynthesis and calcification in the calcifying algae Halimeda macroloba and Halimeda cylindracea and the symbiont-bearing benthic foraminifera Marginopora vertebralis were investigated through exposure to a combination of four temperatures (28 degrees C, 30 degrees C, 32 degrees C, and 34 degrees C) and four CO(2) levels (39, 61, 101, and 203 Pa; pH 8.1, 7.9, 7.7, and 7.4, respectively). Elevated CO(2) caused a profound decline in photosynthetic efficiency (F(V) : F(M)), calcification, and growth in all species. After five weeks at 34 degrees C under all CO(2) levels, all species died. Chlorophyll (Chl) a and b concentration in Halimeda spp. significantly decreased in 203 Pa, 32 degrees C and 34 degrees C treatments, but Chl a and Chl c(2) concentration in M. vertebralis was not affected by temperature alone, with significant declines in the 61, 101, and 203 Pa treatments at 28 degrees C. Significant decreases in F(V) : F(M) in all species were found after 5 weeks of exposure to elevated CO(2) (203 Pa in all temperature treatments) and temperature (32 degrees C and 34 degrees C in all pH treatments). The rate of oxygen production declined at 61, 101, and 203 Pa in all temperature treatments for all species. The elevated CO(2) and temperature treatments greatly reduced calcification (growth and crystal size) in M. vertebralis and, to a lesser extent, in Halimeda spp. These findings indicate that 32 degrees C and 101 Pa CO(2), are the upper limits for survival of these species on Heron Island reef, and we conclude that these species will be highly vulnerable to the predicted future climate change scenarios of elevated temperature and ocean acidification.
Staal, M, Borisov, SM, Rickelt, LF, Klimant, I & Kuhl, M 2011, 'Ultrabright planar optodes for luminescence life-time based microscopic imaging of O2 dynamics in biofilms', Journal of Microbiological Methods, vol. 85, no. 1, pp. 67-74.
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New transparent optodes for life-time based microscopic imaging of O-2 were developed by spin-coating a mu m-thin layer of a highly luminescent cyclometalated iridium(III) coumarin complex in polystyrene onto glass cover slips. Compared to similar thin-film O-2 optodes based on a ruthenium(II) polypyridyl complex or a platinum(II) porphyrin, the new planar sensors have i) higher brightness allowing for much shorter exposure times and thus higher time resolution, ii) more homogeneous and smaller pixel to pixel variation over the sensor area resulting in less noisy O-2 images, and iii) a lower temperature dependency simplifying calibration procedures. We used the new optodes for microscopic imaging of the spatio-temporal O-2 dynamics at the base of heterotrophic biofilms in combination with confocal imaging of bacterial biomass and biofilm structure. This allowed us to directly link biomass distribution to O-2 distribution under both steady state and non-steady state conditions. We demonstrate that the O-2 dynamics in biofilms i; governed by a complex interaction between biomass distribution, mass transfer and flow that cannot be directly inferred from structural information on biomass distribution alone.
Staal, M, Prest, E, Vrouwenvelder, J, Rickelt, LF & Kuhl, M 2011, 'A simple optode based method for imaging O2 distribution and dynamics in tap water biofilms', Water Research, vol. 45, pp. 5027-5037.
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A ratiometric luminescence intensity imaging approach is presented, which enables spatial O2 measurements in biofilm reactors with transparent planar O2 optodes. Optodes consist of an O2 sensitive luminescent dye immobilized in a 1e10 mm thick polymeric layer on a transparent carrier, e.g. a glass window. The method is based on sequential imaging of the O2 dependent luminescence intensity, which are subsequently normalized with luminescent intensity images recorded under anoxic conditions. We present 2-dimensional O2 distribution images at the base of a tap water biofilm measured with the new ratiometric method and compare the results with O2 distribution images obtained in the same biofilm reactor with luminescence lifetime imaging. Using conventional digital cameras, such simple normalized luminescence intensity imaging can yield images of 2-dimensional O2 distributions with a high signal-to-noise ratio and spatial resolution comparable or even surpassing those obtained with expensive and complex luminescence lifetime imaging systems. The method can be applied to biofilm growth incubators allowing intermittent experimental shifts to anoxic conditions or in systems, in which the O2 concentration is depleted during incubation.
Steinke, M, Brading, P, Kerrison, P, Warner, ME & Suggett, DJ 2011, 'Concentrations of dimethylsulfoniopropionate and dimethyl sulfide are strain-specific in symbiotic dinoflagellates (Symbiodinium sp., Dinophyceae)', Journal Of Phycology, vol. 47, no. 4, pp. 775-783.
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Dimethyl sulfide (DMS) and dimethylsulfoniopropionate (DMSP) are sulfur compounds that may function as antioxidants in algae. Symbiotic dinoflagellates of the genus Symbiodinium show strain-specific differences in their susceptibility to temperature-induced oxidative stress and have been shown to contain high concentrations of DMSP. We investigated continuous cultures of four strains from distinct phylotypes (A1, A13, A2, and B1) that can be characterized by differential thermal tolerances. We hypothesized that strains with high thermal tolerance have higher concentrations of DMSP and DMS in comparison to strains with low thermal tolerance. DMSP concentrations were strain-specific with highest concentrations occurring in A1 (225 +/- 3.5 mmol . L(-1) cell volume [CV]) and lowest in A2 (158 +/- 3.8 mmol L) 1 CV). Both strains have high thermal tolerance. Strains with low thermal tolerance (A13 and B1) showed DMSP concentrations in between these extremes (194 +/- 19.0 and 160 +/- 6.1 mmol L(-1) CV, respectively). DMS data further confirmed this general pattern with high DMS concentrations in A1 and A13 (4.1 +/- 1.22 and 2.1 +/- 0.37 mmol . L(-1) CV, respectively) and low DMS concentrations in A2 and B1 (0.3 +/- 0.06 and 0.5 +/- 0.22 mmol . L(-1) CV, respectively). Hence, the strain-specific differences in DMSP and DMS concentrations did not match the different abilities of the four phylotypes to withstand thermal stress. Future work should quantify the possible dynamics in DMSP and DMS concentrations during periods of high oxidative stress in Symbiodinium sp. and address the role of these antioxidants in zooxanthellate cnidarians.
Stuken, A, Orr, RJ, Kellmann, R, Murray, SA, Neilan, BA & Jakobsen, KS 2011, 'Discovery of nuclear-encoded genes for the neurotoxin saxitoxin in dinoflagellates', Plos One, vol. 6, no. 5, pp. e20096-0.
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Saxitoxin is a potent neurotoxin that occurs in aquatic environments worldwide. Ingestion of vector species can lead to paralytic shellfish poisoning, a severe human illness that may lead to paralysis and death. In freshwaters, the toxin is produced by p
Suggett, DJ & Smith, DJ 2011, 'Interpreting the sign of coral bleaching as friend vs. foe', Global Change Biology, vol. 17, no. 1, pp. 45-55.
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Coral bleaching is a major concern to researchers, conservationists and the general public worldwide. To date, much of the high profile attention for bleaching has coincided with major environmental impacts and for many the term coral bleaching is synonymously associated with coral mortality (so-called `lethal bleaching episodes). While this synonymous association has undoubtedly been key in raising public support, it carries unfair representation: nonlethal bleaching is, and always has been, a phenomenon that effectively occurs regularly in nature as corals acclimatize to regular periodic changes in growth environment (days, seasons etc). In addition, corals can exhibit sublethal bleaching during extreme environmental conditions whereby mortality does not occur and corals can potentially subsequently recover once ambient environmental conditions return. Perhaps not surprisingly it is the frequency and extent of these non and sublethal processes that yield key evidence as to how coral species and reef systems will likely withstand environmental and thus climatic change. Observations of non and sublethal bleaching (and subsequent recovery) are arguably not as readily reported as those of lethal bleaching since (1) the convenient tools used to quantify bleaching yield major ambiguity (and hence high potential for misidentification) as to the severity of bleaching; and (2) lethal bleaching events inevitably receive higher profile (media) attention and so are more readily reported. Under-representation of non and sublethal bleaching signs may over-classify the severity of bleaching, under-estimate the potential resilience of reefs against environmental change, and thus ultimately limit (if not depreciate) the validity and effectiveness of reef management policies and practices. While bleaching induced coral mortality must remain our key concern it must be better placed within the context of bleaching signs that do not result in a long-term loss of reefviability.
Tao, L, Chen, G, Zhao, L, Xu, J, Huang, E, Liu, A, Marquis, CP & Davis, TP 2011, 'Protein Release from Biodegradable PolyHPMA-Lysozyme Conjugates Resulting in Bioactivity Enhancement', Chemistry - An Asian Journal, vol. 6, no. 6, pp. 1398-1404.
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Thompson, P, Bonham, P, Waite, A, Clementson, L, Cherukuru, N, Hassler, CS & Doblin, MA 2011, 'Contrasting Oceanographic Conditions And Phytoplankton Communities On The East And West Coasts Of Australia', Deep-Sea Research Part Ii-Topical Studies In Oceanography, vol. 58, no. 5, pp. 645-663.
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The composition and dynamics of the phytoplankton communities and hydrographic factors that control them are described for eastern and western Australia with a focus on the Eastern Australian Current (EAC) and Leeuwin Current (LC) between 27.5 degrees and 34.51S latitude.
Trampe, E, Kolbowski, J, Schreiber, U & Kuhl, M 2011, 'Rapid assessment of different oxygenic phototrophs and single-cell photosynthesis with multicolour variable chlorophyll fluorescence imaging', Marine Biology, vol. 158, no. 7, pp. 1667-1675.
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We present a new system for microscopic multicolour variable chlorophyll fluorescence imaging of aquatic phototrophs. The system is compact and portable and enables microscopic imaging of photosynthetic performance of individual cells and chloroplasts using different combinations of blue, green, red or white light. Automated sequential exposure of microscopic samples to the three excitation colours enables subsequent deconvolution of the resulting fluorescence signals and colour marking of cells with different photopigmentation, i.e., cyanobacteria, green algae, red algae and diatoms. The photosynthetic activity in complex mixtures of phototrophs and natural samples can thus be assigned to different types of phototrophs, which can be quantified simultaneously. Here, we describe the composition and performance of the new imaging system and present applications with both natural phytoplankton and microalgal culture samples.
Trivedi, N, Gupta, V, Kumar, M, Kumari, P, Reddy, CRK & Jha, B 2011, 'An alkali-halotolerant cellulose from Bacillus flexus isolated from green seaweed Ulva lactuca.', Carbohydrate Polymers, vol. 83, no. 2, pp. 891-897.
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Abstract
An extracellular alkali-halotolerant cellulase from the strain Bacillus flexus NT isolated from Ulva lactuca was purified to homogeneity with a recovery of 25.03% and purity fold of 22.31. The molecular weight of the enzyme was about 97 kDa and the Vmax and Km was 370.17 U/ml/min and 6.18 mg/ml respectively. The optimum pH and temperature for enzyme activity was 10 and 45 °C respectively. The enzymatic hydrolysis of the CMC was confirmed with GPC and GC-MS analysis. The stabilized activity of the enzyme even at high pH of 9.0–12.0 and residual activity of about 70% at salt concentration (NaCl 15%) revealed for its alkali-halotolerance nature. The metal ions Cd2+ and Li1+ were found as inducers while Cr2+, Co2+, Zn2+ and metal chelator EDTA have significantly inhibited the enzyme activity. Enzyme activity was insensitive to ethanol and isopropanol while partially inhibited by acetone, cyclohexane and benzene.
Trivedi, N, Gupta, V, Kumar, M, Kumari, P, Reddy, CRK & Jha, B 2011, 'Solvent tolerant marine bacterium Bacillus aquimaris secreting organic solvent stable alkaline cellulase', CHEMOSPHERE, vol. 83, no. 5, pp. 706-712.
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Ulstrup, K, Kuhl, M, van Oppen, MJ, Cooper, TF & Ralph, PJ 2011, 'Variation in photosynthesis and respiration in geographically distinct populations of two reef-building coral species', Aquatic Biology, vol. 12, pp. 241-248.
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Studies of the regulation and importance of physiological processes such as coral photosynthesis and respiration on coral reefs require knowledge of spatio-temporal patterns of variability at different scales. Oxygen microelectrodes were used to measure photosynthesis and dark respiration of 2 corals, Pocillopora damicornis and Turbinaria reniformis, in the northern (Lizard Island) and central (Davies and Broadhurst Reefs) regions of the Great Barrier Reef (GBR) in winter and summer. Genetic characterisation of Symbiodinium revealed that P. damicornis hosted a single symbiont type (Symbiodinium C1) in both regions, whereas T. reniformis harboured 2 types, dependent on location. Colonies at Lizard Island harboured Symbiodinium D, whereas colonies at Davies Reef harboured Symbiodinium C2. Rates of gross photosynthesis were greater in the central than in the northern GBR in summer. A similar pattern was detected for dark respiration rates in T. reniformis. No seasonal change in either photosynthesis or dark respiration was evident in the northern GBR, possibly due to less annual variability in light conditions, and for T. reniformis, additionally the presence of Symbiodinium D. These results highlight that environmental conditions coupled with regional-scale distribution of Symbiodinium are likely to exert important influences on respiration and photosynthetic performance of reef-building corals.
Velikova, V, Varkonyi, Z, Szabo, M, Maslenkova, L, Nogues, I, Kovacs, L, Peeva, V, Busheva, M, Garab, G, Sharkey, TD & Loreto, F 2011, 'Increased thermostability of thylakoid membranes in isoprene-emitting leaves probed with three biophysical techniques', Plant Physiology, vol. 157, pp. 905-916.
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Three biophysical approaches were used to get insight into increased thermostability of thylakoid membranes in isoprene- emittingplants.Arabidopsis (Arabidopsis thaliana) plants genetically modified to make isoprene and Platanus orientalis leaves, in which isoprene emission was chemically inhibited, were used. First, in the circular dichroism spectrum the transition temperature of the main band at 694 nm was higher in the presence of isoprene, indicating that the heat stability of chiral macrodomains of chloroplast membranes, and specifically the stability of ordered arrays of light-harvesting complex IIphotosystem II in the stacked region of the thylakoid grana, was improved in the presence of isoprene. Second, the decay of electrochromic absorbance changes resulting from the electric field component of the proton motive force (DA515) was evaluated following single-turnover saturating flashes. The decay of DA515 was faster in the absence of isoprene when leaves of Arabidopsis and Platanus were exposed to high temperature, indicating that isoprene protects the thylakoid membranes against leakiness at elevated temperature. Finally, thermoluminescence measurements revealed that S2QB 2 charge recombination was shifted to higher temperature in Arabidopsis and Platanus plants in the presence of isoprene, indicating higher activation energy for S2QB 2 redox pair, which enables isoprene-emitting plants to perform efficient primary photochemistry of photosystem II even at higher temperatures. The data provide biophysical evidence that isoprene improves the integrity and functionality of the thylakoid membranes at high temperature. These results contribute to our understanding of isoprene mechanism of action in plant protection against environmental stresses.
Weatherby, K, Murray, SA, Carter, D & Slapeta, J 2011, 'Surface and flagella morphology of the motile form of Chromera velia revealed by field-emission scanning electron microscopy', Protist, vol. 162, no. 1, pp. 142-153.
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Chromera velia (Chromerida; Alveolata) is an autotrophic protist isolated from stony corals. Ch. velia possesses a chloroplast thought to be most closely related to the apicoplasts of non-photosynthetic apicomplexa. Phylogenetic analyses place Ch. velia as a close relative of parasitic apicomplexa and predatory colpodellids. We have used field-emission scanning electron microscopy of cells sputter-coated with gold or chromium and non-coated cells to characterise the surface ultrastructure of the motile form of Ch. velia. In overall morphology the biflagellated Ch. velia cells resemble the colpodellid Colpodella edax, but with some notable differences. The ventral side of the flagellated Ch. velia cell has two grooves extending from the anterior flagella insertion point with a ridge rising towards the anterior apex of the cell. The anterior flagellum is shorter than the posterior flagellum and possesses a distinct, small curved appendage. The insertion point of the anterior flagellum is partly enclosed by a flap extending from the cell. The posterior flagellum is approximately four times the length of the cell and possesses mastigonemes. The combination of coating techniques proved superior to the commonly used gold coating to determine fine surface ultrastructure. This new ultrastructural information for Ch. velia allowed us to emend its diagnosis.