Ashworth, J, Havranek, JJ, Duarte, CM, Sussman, D, Monnat, RJ, Stoddard, BL & Baker, D 2006, 'Computational redesign of endonuclease DNA binding and cleavage specificity', NATURE, vol. 441, no. 7093, pp. 656-659.
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Belli, SI, Smith, NC & Ferguson, DJ 2006, 'The coccidian oocyst a tough nut to crack!', Trends In Parasitology, vol. 22, no. 9, pp. 416-423.
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Coccidian parasites are transmitted between hosts by the ingestion of food or water contaminated with oocysts, followed by the release of infectious sporozoites and invasion of the gastro-intestinal tract. In the external environment, sporozoites are pro
Ben-Dov, E, Shapiro, OH, Siboni, N & Kushmaro, A 2006, 'Advantage of using inosine at the 3 ' termini of 16S rRNA gene universal primers for the study of microbial diversity', APPLIED AND ENVIRONMENTAL MICROBIOLOGY, vol. 72, no. 11, pp. 6902-6906.
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Charles, AL, Markich, SJ & Ralph, PJ 2006, 'Toxicity of uranium and copper individually, and in combination, to a tropical freshwater macrophyte (Lemna aequinoctialis)', Chemosphere, vol. 62, no. 8, pp. 1224-1233.
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Copper (Cu) and uranium (U) are of potential ecotoxicological concern to tropical freshwater biota in northern Australia, as a result of mining activities. Few data are available on the toxicity of U, and no data are available on the toxic interaction of
Dela-Cruz, J, Pritchard, T, Gordon, G & Ajani, PA 2006, 'The use of periphyton as a means of assessing impacts of point source inorganic nutrient pollution in south-eastern Australia.', Freshwater Biology, vol. 51, no. 5, pp. 951-972.
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Summary
1. Periphytic diatoms are used as indicators of water quality because their ecological tolerances or preferences to environmental variables are thought to be predictable. However, much of the present autecological information for periphytic diatoms has been derived from studies conducted in the northern hemisphere. In this present study we used periphytic diatoms to determine the impacts of inorganic nutrient pollution in a tidal river system in the temperate latitudes of south-east Australia. In so doing, we assess the suitability of the use of the ‘northern hemisphere’ ecological tolerance/preference data for periphytic diatoms.
2. Artificial substrates were used to collect periphytic diatoms at 35 sites, which were positioned along the riverbanks and the middle of the river at various distances upstream and downstream of the sewage outfall. The sampling design took into account tidal excursions and the observed sewage plume dynamics. Periphytic diatoms were collected during the austral winter month of August and the austral spring months of September and October. We deployed the artificial substrates for 4 weeks to allow the periphytic diatoms to recruit and colonise, before identifying and enumerating the assemblages.
3. Data analysis included two approaches: multivariate visualisations of combinations of environmental and biological data to investigate shifts in species structure of the periphytic diatom assemblage and multimetric indices based on ecological tolerance/preference data.
4. We found that the spatial patterns inferred from multivariate and multimetric analyses were consistent. Temporal variation in the composition of the periphytic diatom assemblage was greater than the spatial variation along horizontal sections of the river (in any one deployment) due mainly to shifts between winter and spring species.
5. Outfall effects were most apparent in winter, possibly because subsequent deployments were swamped by growth of spring periphyt...
Doblin, MA & Dobbs, FC 2006, 'Setting a size-exclusion limit to remove toxic dinoflagellate cysts from ships ballast water', Marine Pollution Bulletin, vol. 52, no. 3, pp. 259-263.
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Dinoflagellate cysts are well-recognized biological constituents of ships ballast tanks. They are present in ballast water, sediments and residual water in drained tanks, and in biofilms formed on interior tank Surfaces. Therefore, cysts have the potenti
Doblin, MA, Baines, SB, Cutter, LS & Cutter, GA 2006, 'Sources and biogeochemical cycling of particulate selenium in the San Francisco Bay estuary', Estuarine Coastal And Shelf Science, vol. 67, no. 4, pp. 681-694.
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As part of a study of estuarine selenium cycling, we measured the concentration, chemical form (speciation), and distribution of particulate selenium under various river flow conditions in the North San Francisco Bay (from the Golden Gate to the Sacramen
Doblin, MA, Thompson, P, Revill, A, Butler, E, Blackburn, S & Hallegraeff, GM 2006, 'Vertical migration of the toxic dinoflagellate Gymnodinium catenatum under different concentrations of nutrients and humic substances in culture', Harmful algae, vol. 5, no. 6, pp. 665-677.
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Vertical migration behaviour by the chainforming dinoflagellate Gymnodinium catenatum Graham was investigated using vertically-stratified laboratory columns. Under surface nutrient-deplete conditions, with nutrients added only at depth, 100% of cells underwent vertical migration (VM), starting downwards migration 3 h before the end of the light period and beginning upwards migration 3 h before the start of the light period. Cells in nutrient-replete columns showed no VM, but they were more dispersed in the upper layer during the dark compared to the light period. When surface layers (S) were nitrate-deplete (-N) and enriched with humic substances (H) contained in Huon River water and bottom waters (B) were nutrient replete (R) (SH-NBR), the pattern of VM was altered-50% of cells underwent migration and 50% remained at the pycnocline. In columns with nitrate-replete and humic-enriched surface layers (SHRBR), Most cells underwent VM, while 30% remained at the surface. Cells in SH-NBR columns showed increased N quotas and intra-cellular nitrate concentrations after 4 days, indicating nitrate uptake by G. catenatum in bottom layers. The concomitant increase in particulate organic nitrogen (PON) with the decrease in external nitrate concentrations in bottom layers provide convincing evidence that VM by G. catenatum facilitates nutrient retrieval at depth. However, addition of humic substances (a potential source of organic nitrogen) to surface layers did not ameliorate G. catenatum N depletion sufficiently to preclude the need for NO3- uptake at depth. Furthermore, there was no detectable pattern of increasing carbon (C) quota during the day (photosynthate accumulation) or increasing N quota during the night (nitrate assimilation).
Doubell, MJ, Seuront, L, Seymour, JR, Patten, NL & Mitchell, JG 2006, 'High-Resolution Fluorometer for Mapping Microscale Phytoplankton Distributions', Applied and Environmental Microbiology, vol. 72, no. 6, pp. 4475-4478.
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A new high-resolution, in situ profiling fluorometer maps fluorescence distributions with a spatial resolution of 0.5 to 1.5 mm to a depth of 70 m in the open ocean. We report centimeter-scale patterns for phytoplankton distributions associated with gradients exhibiting 10- to 30-fold changes in fluorescence in contrasting marine ecosystems.
Handy, SM, Coyne, KJ, Portune, KJ, Demir, E, Doblin, MA, Hare, CE, Cary, SC & Hutchins, DA 2006, 'Erratum: Evaluating vertical migration behavior of harmful raphidophytes in the Delaware Inland Bays utilizing quantitative real-time PCR (Aquatic Microbial Ecology (2005) 40, (121-132))', Aquatic Microbial Ecology, vol. 42, no. 3, p. 311.
Hill, R & Ralph, PJ 2006, 'Photosystem II Heterogeneity of in hospite Zooxanthellae in Scleractinian Corals Exposed to Bleaching Conditions', Photochemistry and Photobiology, vol. 82, no. 6, pp. 1577-1585.
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Increased ocean temperatures are thought to be triggering mass coral bleaching events around the world. The intracellular symbiotic zooxanthellae (genus Symbiodinium) are expelled from the coral host, which is believed to be a response to photosynthetic damage within these symbionts. Several sites of impact have been proposed, and here we probe the functional heterogeneity of Photosystem II (PSII) in three coral species exposed to bleaching conditions. As length of exposure to bleaching conditions (32 degrees C and 350 mu mol photons m(-2) s(-1)) increased, the Q(A)(-) reoxidation kinetics showed a rise in the proportion of inactive PSII centers (PSIIX), where Q(B) was unable to accept electrons. PSIIX contributed up to 20% of the total PSII centers in Pocillopora damicornis, 35% in Acropora nobilis and 14% in Cyphastrea serailia. Changes in F-V/F-M and amplitude of the J step along fast induction curves were found to be highly dependent upon the proportion of PSIIx centers within the total pool of PSII reaction centers. Determination of PSII antenna size revealed that under control conditions in the three coral species up to 60% of PSII centers were lacking peripheral light-harvesting complexes (PSII beta). In P. damicornis, the proportion of PSII beta increased under bleaching conditions and this could be a photoprotective mechanism in response to excess light. The rapid increases in PSIIX and PSII beta observed in these corals under bleaching conditions indicates these physiological processes are involved in the initial photochemical damage to zooxanthellae.
Jones, H, Ostrowski, M & Scanlan, DJ 2006, 'A suppression subtractive hybridization approach reveals niche-specific genes that may be involved in predator avoidance in marine Synechococcus isolates', APPLIED AND ENVIRONMENTAL MICROBIOLOGY, vol. 72, no. 4, pp. 2730-2737.
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Kohler-Rink, S & Kuhl, M 2006, 'The chemical microenvironment of the symbiotic planktonic foraminifer Orbulina universa', Marine Biology Research, vol. 1, no. 1, pp. 68-78.
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Microsensor measurements of CO2, O2, pH and Ca2 in the vicinity of the symbiont-bearing planktonic foraminifer Orbulina universa showed major light-modulated changes in the chemical microenvironment due to symbiont photosynthesis, respiration of the holobiont, and precipitation of the calcite shell. Under saturating light conditions, microprofiles measured towards the shell surface showed an O2 increase of up to 220% air saturation, a decrease in CO2 concentration to 4.9 mM, and a pH increase to 8.8 due to symbiont photosynthesis. The Ca2 concentration decreased to /9.6 mM in two specimens, while it increased to 10.2/10.8 mM in three other specimens kept in light. In darkness, the respiration of the community decreased the O2 concentration to 82% of air saturation, CO2 increased up to 15 mM, the pH decreased to 8.0, and the Ca2 concentration increased up to 10.4 mM. These data, and derived calculations of the distribution of HCO3 and CO3 2 near the shell, showed that the carbonate system in the vicinity of O. universa was significantly different from conditions in the surrounding seawater, both in light and darkness, due to the metabolism of the foraminifer and its associated algae. Experimental light/dark cycles indicated a sufficient CO2 supply sustaining high carbon fixation rates of the symbiotic algae via conversion of HCO3 or via CO2 release from calcification and host respiration. Our findings on irradiance-dependent CO2 and pH changes in the vicinity of symbiont-bearing planktonic foraminifera give direct experimental evidence for the predictions of isotope fractionation models used in palaeoclimatology stating that metabolic processes affect the isotopic carbon signal (d13C) in foraminifera.
Kramarsky-Winter, E, Harel, M, Siboni, N, Ben Dov, E, Brickner, I, Loya, Y & Kushmaro, A 2006, 'Identification of a protist-coral association and its possible ecological role', MARINE ECOLOGY PROGRESS SERIES, vol. 317, pp. 67-73.
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Moore, CM, Suggett, DJ, Hickman, AE, Kim, Y, Tweddle, JF, Sharples, J, Geider, RJ & Holligan, PM 2006, 'Phytoplankton photoacclimation and photoadaptation in response to environmental gradients in a shelf sea', Limnology And Oceanography, vol. 51, no. 2, pp. 936-949.
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Variability in the photosynthetic performance of natural phytoplankton communities, due to both taxonomic composition and the physiological acclimation of these taxa to environmental conditions, was assessed at contrasting sites within a temperate shelf
Murray, SA, Hoppenrath, M, Larsen, J & Patterson, DJ 2006, 'Bysmatrum teres sp. nov., a new sand-dwelling dinoflagellate from north-western Australia', Phycologia, vol. 45, no. 2, pp. 161-167.
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Murray, SA, Hoppenrath, M, Preisfeld, A, Larsen, J, Yoshimatsu, S, Toriumi, S & Patterson, DJ 2006, 'Phylogenetics of Rhinodinium broomeense gen. et sp. nov., a peridinoid, sand-dwelling dinoflagellate (Dinophyceae)', Journal of Phycology, vol. 42, pp. 934-942.
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O'Meara, T, Green, BJ, Sercombe, J & Tovey, E 2006, 'Measurement of personal exposure to outdoor aeromycota in northern New South Wales, Australia', vol. 13, no. 2, pp. 225-234.
Oren A, Pri-El N, Shapiro O & Siboni, N 2006, 'Buoyancy studies in natural communities of square gas-vacuolate archaea in saltern crystallizer ponds', Saline Systems, vol. 2.
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Patten, NL, Seymour, JR & Mitchell, JG 2006, 'Flow cytometric analysis of virus-like particles and heterotrophic bacteria within coral-associated reef water', Journal of the Marine Biological Association of the United Kingdom, vol. 86, no. 3, pp. 563-566.
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Using flow cytometry, two distinct populations of virus-like particles (VLP) and heterotrophic bacteria were defined within the 12 cm water layer immediately overlying healthy, diseased and dead acroporid corals. Bacterial abundances were similar in overlying water for all coral types, however, VLP were 30% higher above diseased corals than healthy or dead corals. Mean virus to bacteria ratios (VBR) were up to 30% higher above diseased corals than above healthy or dead coral or in distant water. Concomitant with increasing VLP concentrations within 5 cm of coral surfaces, VBR distributions were generally highest above healthy and diseased coral and depressed above dead coral. These results suggest fundamental shifts in the VLP and bacterial community in water associated with diseased corals.
Pernice, M, Deutsch, JS, Andouche, A, Boucher-Rodoni, R & Bonnaud, L 2006, 'Unexpected variation of Hox genes' homeodomains in cephalopods', MOLECULAR PHYLOGENETICS AND EVOLUTION, vol. 40, no. 3, pp. 872-879.
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Ryan, KG, Hegseth, E, Martin, A, Davy, S, O'Toole, R, Ralph, PJ, McMinn, A & Thorn, C 2006, 'Comparison of the microalgal community within fast ice two sites along the Ross Sea coast, Antarctia', Antarctic Science, vol. 18, no. 4, pp. 583-594.
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Seery, CR, Gunthorpe, L & Ralph, PJ 2006, 'Herbicide impact on Hormosira banksii gametes measured by fluorescence and germination bioassays', Environmental Pollution, vol. 140, no. 1, pp. 43-51.
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The innovative bioassay described here involves chlorophyll a fluorescence measurements of gametes from the macroalgae, Hormosira banksii, where gametes (eggs) were exposed to Diuron, Irgarol and Bromacil. Response was assessed as percent inhibition from
Seymour, JR, Seuront, L, Doubell, MJ, Waters, RL & Mitchell, JG 2006, 'Microscale patchiness of virioplankton', Journal of the Marine Biological Association of the United Kingdom, vol. 86, no. 3, pp. 551-561.
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The microscale spatial distributions of viruses were investigated in three contrasting environments including oligotrophic open ocean, eutrophic coastal and estuarine habitats. The abundances of two discrete populations of both viruses and heterotrophic bacteria were measured at spatial resolutions of between 1 and 5 cm using purpose-designed microscale sampling equipment and flow cytometric sample analysis. Within open water samples, virus distributions were characterized by non-normal distributions and by `hotspots' in abundance where concentrations varied by up to 17-fold. In contrast to patterns generally observed at larger spatiotemporal scales, there was no correlation between bacterial and viral abundance or correspondence between bacteria and virus hotspots within these samples. Consequently, strong hotspots and gradients in the virus:bacteria ratio (VBR) were also apparent within samples. Within vertical pro¢les taken from above the sediment water interface within a temperate mangrove estuary, distributions of planktonic viruses were characterized by gradients in abundance, with highest concentrations observed within the 1-2 cm immediately above the sediment surface, and virus distributions were correlated to bacterial abundance (P50.01). The patterns observed in these contrasting habitats indicate that microscale patchiness of virus abundance may be a common feature of the marine environment. This form of heterogeneity may have important implications for virus^host dynamics and subsequently in£uence microbial trophodynamics and nutrient cycling in the ocean.
Steunou, A, Bhaya, D, Bateson, MM, Melendrez, MC, Ward, DM, Brecht, E, Peters, JW, Kuhl, M & Grossman, AR 2006, 'In situ analysis of nitrogen fixation and metabolic switching in unicellular thermophilic cyanobacteria inhabiting hot spring microbial mats', Proceedings of the National Academy of Sciences, vol. 103, no. 7, pp. 2398-2403.
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Genome sequences of two Synechococcus ecotypes inhabiting the Octopus Spring microbial mat in Yellowstone National Park revealed the presence of all genes required for nitrogenase biosynthesis. We demonstrate that nif genes of the Synechococcus ecotypes are expressed in situ in a region of the mat that varies in temperature from 53.5°C to 63.4°C (average 60°C); transcripts are only detected at the end of the day when the mat becomes anoxic. Nitrogenase activity in mat samples was also detected in the evening. Hitherto, N2 fixation in hot spring mats was attributed either to filamentous cyanobacteria (not present at >50°C in these mats) or to heterotrophic bacteria. To explore how energy-generating processes of the Synechococcus ecotypes track natural light and O2 conditions, we evaluated accumulation of transcripts encoding proteins involved in photosynthesis, respiration, and fermentation. Transcripts from photosynthesis (cpcF, cpcE, psaB, and psbB) and respiration (coxA and cydA) genes declined in the evening. In contrast, transcripts encoding enzymes that may participate in fermentation fell into two categories; some (ldh, pdhB, ald, and ackA) decreased in the evening, whereas others (pflB, pflA, adhE, and acs) increased at the end of the day and remained high into the night. Energy required for N2 fixation during the night may be derived from fermentation pathways that become prominent as the mat becomes anoxic. In a broader context, our data suggest that there are critical regulatory switches in situ that are linked to the diel cycle and that these switches alter many metabolic processes within the microbial mat.
Suggett, DJ, Maberly, SC & Geider, RJ 2006, 'Gross photosynthesis and lake community metabolism during the spring phytoplankton bloom', Limnology And Oceanography, vol. 51, no. 5, pp. 2064-2076.
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Daily productivity determinations of linear photosynthetic electron transfer and of net and gross inorganic CO2 uptake were determined in situ throughout a 6-week sampling period of the spring phytoplankton bloom in Esthwaite Water in the English Lake Di
Suggett, DJ, Moore, CM, Maranon, E, Omachi, C, Varela, RA, Aiken, J & Holligan, PM 2006, 'Photosynthetic electron turnover in the tropical and subtropical Atlantic Ocean', Deep Sea Research Part II: Topical Studies in Oceanography, vol. 53, no. 14-16, pp. 1573-1592.
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Photosynthetic electron transport directly generates the energy required for carbon fixation and thus underlies the aerobic metabolism of aquatic systems. We determined photosynthetic electron turnover rates, ETRs, from ca. 100 FRR fluorescence water-column profiles throughout the subtropical and tropical Atlantic during six Atlantic Meridional Transect cruises (AMT 6, MayJune 1998, to AMT 11, SeptemberOctober 2000). Each FRR fluorescence profile yielded a water-column ETR-light response from which the maximum electron turnover rate (ETRRCIImax), effective absorption (s PSII) and light saturation parameter (E k) specific to the concentration of photosystem II reaction centres (RCIIs) were calculated. ETRRCIImax and E k increased whilst s PSII decreased with mixed-layer depth and the daily integrated photosynthetically active photon flux when all provinces were considered together. These trends suggested that variability in maximum ETR can be partly attributed to changes in effective absorption. Independent bio-optical measurements taken during AMT 11 demonstrated that s PSII variability reflects taxonomic and physiological differences in the phytoplankton communities. ETRRCIImax and Ek, but not sPSII, remained correlated with mixed-layer depth and daily integrated photosynthetically active photon flux when data from each oceanic province were considered separately, indicating a decoupling of electron turnover and carbon fixation rates within each province. Comparison of maximum ETRs with 14C-based measurements of Pmax further suggests that light absorption and C fixation are coupled to differing extents for the various oligotrophic Atlantic provinces. We explore the importance of quantifying RCII concentration for determination of ETRs and interpretation of ETR-C fixation coupling.
Ulstrup, K, Berkelmans, R, Ralph, PJ & van Oppen, MJ 2006, 'Variation in bleaching sensitivity of two coral species across a latitudinal gradient on the Great Barrier Reef: the role of zooxanthellae', Marine Ecology Progress Series, vol. 314, pp. 135-148.
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The ability of corals to cope with environmental change, such as increased temperature, relies on the physiological mechanisms of acclimatisation and long-term genetic adaptation. We experimentally examined the bleaching sensitivity exhibited by 2 species of coral, Pocillopora damicornis and Turbinaria reniformis, at 3 locations across a latitudinal gradient of almost 6 degrees on the Great Barrier Reef (GBR), Target bleaching temperature was reached by using a ramping rate of 0.2 degrees C/h. We found that the bleaching sensitivity and recovery of both species differed between corals with clade D symbionts and those with clade C. However, in F damicornis bleaching susceptibility corresponded more strongly with latitude than with zooxanthella type and hence, temperature history, suggesting that local adaptation has occurred. The observed bleaching sensitivity was shown by a decrease in photochemical efficiency (F-v/F-m) in both species of coral. The rate of recovery in T reniformis was highest in explants containing clade D symbionts. The occurrence of clade D in the northern section of the GBR may reflect a long-term response to high sea water temperatures, while the presence of clade D in low abundance in T reniformis at Heralds Prong Reef and Percy Island may be a result of recent bleaching events.
Ulstrup, K, Ralph, PJ, Larkum, A & Kuhl, M 2006, 'Intra-colonial variability in light acclimation of zooxanthellae in coral tissues of Pocillopora damicornis Received:', Marine Biology, vol. 149, pp. 1325-1335.
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Ward, DM, Bateson, MM, Ferris, MJ, Kuhl, M, Wieland, A, Koeppel, A & Cohan, FM 2006, 'Cyanobacterial ecotypes in the microbial mat community of Mushroom Spring (Yellowstone National Park, Wyoming) as species-like units linking microbial community composition, structure and function', Philosophical Transactions of the Royal Society B, vol. 361, no. 1475, pp. 1997-2008.
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We have investigated microbial mats of alkaline siliceous hot springs in Yellowstone National Park as natural model communities to learn how microbial populations group into species-like fundamental units. Here, we bring together empirical patterns of the distribution of molecular variation in predominant mat cyanobacterial populations, theory-based modelling of how to demarcate phylogenetic clusters that correspond to ecological species and the dynamic patterns of the physical and chemical microenvironments these populations inhabit and towards which they have evolved adaptations. We show that putative ecotypes predicted by the theory-based model correspond well with distribution patterns, suggesting populations with distinct ecologies, as expected of ecological species. Further, we show that increased molecular resolution enhances our ability to detect ecotypes in this way, though yet higher molecular resolution is probably needed to detect all ecotypes in this microbial community.
Wieland, A & Kuhl, M 2006, 'Regulation of photosynthesisand oxygen consumption ina hypersaline cyanobacterialmat (Camargue, France)byirradiance, temperatureandsalinity', F E M S Microbiology Ecology, vol. 55, no. 2, pp. 195-210.
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Short-term effects of irradiance (01560 ?mol photons m-2 s-1), temperature (1025°C), and salinity (40160) on oxygenic photosynthesis and oxygen consumption in a hypersaline mat (Salin-de-Giraud, France) were investigated with microsensors under controlled laboratory conditions. Dark O2 consumption rates were mainly regulated by the mass transfer limitations imposed by the diffusive boundary layer. Areal rates of net photosynthesis increased with irradiance and saturated at irradiances >400 ?mol photons m-2 s-1. At low irradiances, oxygen consumption increased more strongly with temperature than photosynthesis, whereas the opposite was observed at saturating irradiances. Net photosynthesis vs. irradiance curves were almost unaffected by decreasing salinity (100 to 40), whereas increasing salinities (100 to 160) led to a decrease of net photosynthesis at each irradiance. Dark O2 consumption rates, maximal gross and net photosynthesis at light saturation were relatively constant over a broad salinity range (60100) and decreased at salinities above the in situ salinity of 100. Within the range of natural variation, temperature was more important than salinity in regulating photosynthesis and oxygen consumption. At higher salinities the inhibitory impact of salinity on these processes and therefore the importance of salinity as a regulating environmental parameter increased, indicating that in more hypersaline systems, salinity has a stronger limiting effect on microbial activity.
Willhelm, S, Carberry, M, Eldridge, M, Poorvin, L, Saxton, M & Doblin, MA 2006, 'Marine and Freshwater Cyanophages in a Laurentian Great Lake: Evidence from Infectivity Assays and Molecular Anayses of g20 genes', Applied and Environmental Microbiology, vol. 72, no. 7, pp. 4957-4963.
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While it is well established that viruses play an important role in the sturcture of marine microbisal food webs, few studies have directly addresed their role in large lake systems. As part of an ongoing study of the microbial acology of Lake Erie, we have examined the distribution and diversity of viruses in this system. One surprising result has bee the pervasive distribution of cyanophages that infect the marine cyanobacterial isolate Synechococcus sp. strain WH7803. Viruses that typically infect this cyanobacterium wre identified throughout the western basin of Lake Erie, as well as in locations within the central and eastern basins. Analyses of the gene encoding the g20 viral capsid assembly protein (a conservative phylogenetic marker for the cyanophage) indicate that these viruses as well as amplicons from natural populations and the ballast of commercial ships are related to marine cyanophages but in some cases form a unique clade, leaving questions concerning the native hosts of these viruses. The results suggest that cyanophages may be as important in freshwater systems as they are known to be in marine systems.