Belli, SI 2000, 'Chromatin Remodelling During the Life Cycle of Trypanosomatids', International Journal for Parasitology, vol. 30, no. 0, pp. 679-687.
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The mechanisms which control the expression of developmentally regulated genes in trypanosomatids remain unclear. The genes are grouped together into transcription units that are co-transcribed to yield polycistronic RNAs. Trans-splicing and polyadenylation give rise to mature, monocistronic mRNAs. It is difficult to imagine that expression of these genes is controlled at the level of transcription initiation because this would suggest that the genes are transcribed at the same rate. This is not the case, because at any given developmental stage in trypanosomes or Leishmania, genes transcribed from the same transcription unit are expressed at different levels within the cell. Consequently, these parasites must rely on post-transcriptional or post-translational mechanisms to generate the appropriate levels of gene product within the cell. There are no well-established examples of RNA polymerase II promoters in trypanosomes or Leishmania. However, the promoters for genes encoding the variant surface glycoprotein (VSG) and the procyclic acidic repetitive protein (PARP) have been identified and resemble ribosomal RNA polymerase I promoters. In higher eukaryotes where the mechanisms regulating transcription are clearer, there is increasing evidence that epigenetic factors, such as histones and modified bases, influence gene expression. Chemical modification of these factors can restructure chromatin and lead to gene activation or silencing. In trypanosomatids, an epigenetic mechanism for the control of developmentally expressed genes is a possibility. In this review, chromatin remodelling during the life and cell cycle of trypanosomes and Leishmania is explored, and the influence of epigenetic factors such as histones and modified bases on this process is discussed.
de Beer, D, Kuhl, M, Stambler, N & Vaki, L 2000, 'A microsensor study of light enhanced Ca2+ uptake and photosynthesis in the reef-building hermatypic coral Favia sp.', Marine Ecology Progress Series, vol. 194, pp. 75-85.
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De Lucca, SD, O’Meara, TJ & Tovey, ER 2000, 'Exposure to mite and cat allergens on a range of clothing items at home and the transfer of cat allergen in the workplace', Journal of Allergy and Clinical Immunology, vol. 106, no. 5, pp. 874-879.
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Doblin, MA, Blackburn, S & Hallegraeff, GM 2000, 'Intraspecific variation in the selenium requirement of different geographic strains of the toxic dinoflagellate Gymnodinium catenatum', Journal Of Plankton Research, vol. 22, no. 3, pp. 421-432.
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The requirement for selenium (IV) was assessed in five strains of the toxic dinoflagellate Gymnodinium catenatum Graham, representing three populations from Tasmania (Australia), as well as one each from Japan and Spain. Strains were grown in nutrient-en
Epping, E & Kuhl, M 2000, 'The responses of photosynthesis and oxygen consumption to short-term changes in temperature and irradiance in a cyanobacterial mat (Ebro Delta, Spain)', Environmental Microbiology, vol. 2, no. 4, pp. 465-474.
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We have evaluated the effects of short-term changes in incident irradiance and temperature on oxygenic photosynthesis and oxygen consumption in a hypersaline cyanobacterial mat from the Ebro Delta, Spain, in which Microcoleus chthonoplastes was the dominant phototrophic organism. The mat was incubated in the laboratory at 15, 20, 25 and 30°C at incident irradiances ranging from 0 to 1000 µmol photons m-2 s-1. Oxygen microsensors were used to measure steady-state oxygen profiles and the rates of gross photosynthesis, which allowed the calculation of areal gross photosynthesis, areal net oxygen production, and oxygen consumption in the aphotic layer of the mat. The lowest surface irradiance that resulted in detectable rates of gross photosynthesis increased with increasing temperature from 50 µmol photons m-2 s-1 at 15°C to 500 µmol photons m-2 s-1 at 30°C. These threshold irradiances were also apparent from the areal rates of net oxygen production and point to the shift of M. chthonoplastes from anoxygenic to oxygenic photosynthesis and stimulation of sulphide production and oxidation rates at elevated temperatures. The rate of net oxygen production per unit area of mat at maximum irradiance, J0, did not change with temperature, whereas, JZphot, the flux of oxygen across the lower boundary of the euphotic zone increased linearly with temperature. The rate of oxygen consumption per volume of aphotic mat increased with temperature. This increase occurred in darkness, but was strongly enhanced at high irradiances, probably as a consequence of increased rates of photosynthate exudation, stimulating respiratory processes in the mat. The compensation irradiance (Ec) marking the change of the mat from a heterotrophic to an autotrophic community, increased exponentially in this range of temperatures.
Fenchel, T & Kuhl, M 2000, 'Artificial cyanobacterial mats: growth, structure, and vertical zonation patterns', Microbial Ecology, vol. 40, pp. 85-93.
Field, CD 2000, 'Mangroves', Seas at the millennium - an environmental evaluation - Volume 3, pp. 17-32.
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Mangroves form coastal forests largely confined between 30°north and south of the equator. This range is determined mainly by low and extreme temperatures and, to a lesser extent, by rainfall. They are thus abundant in many lesser developed countries with fast rising populations which exert strong development pressure on this ecosystem. In recent years, pressures of increasing population, food production and development have led to a significant proportion of the world's mangrove resource being destroyed at a rate faster than they are being regenerated. Much of their elimination has been to create land for aquaculture, particularly shrimp ponds, but in many instances shrimp ponds are quickly abandoned as a result of falling production, leaving highly degraded land on which mangroves do not naturally re-establish themselves. It is estimated that shrimp ponds in Asia rarely last for more than five to ten years, leaving irreversibly degraded environments. The scale of mangrove clearance may be huge: in the Philippines, for example 70% were lost in a period of 60 years, and similar or even greater clearance rates have been seen in 'New World' areas too. A popular view of mangrove forests is that they are very productive, and under some conditions they compare well with terrestrial forests. The qualitative importance of mangroves as habitat, nursery and source of food for both commercial fisheries species and other non-commercial fauna is generally accepted, as is the fact that a large number of juvenile fish use mangroves as nursery habitats. However, there is a lack of well established quantified relationships between fish yields and area of mangrove, though several studies support the hypothesis that coastal fish resources are closely linked to estuaries and mangroves, even if controversy remains about their degree of dependence. Apart from being a productive shoreline ecosystem, mangroves can help stabilise dynamic coastlines. There is now an upsurge in the number...
Gibb, SW, Barlow, RG, Cummings, DG, Rees, NW, Trees, CC, Holligan, P & Suggett, D 2000, 'Surface phytoplankton pigment distributions in the Atlantic Ocean: An assessment of basin scale variability between 50°N and 50°S', Progress in Oceanography, vol. 45, no. 3-4, pp. 339-368.
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We present an overview of the spatial distributions of phytoplankton pigments along transects between the UK and the Falkland Islands. These studies, undertaken as a component of the UK Atlantic Meridional Transect (AMT) programme, provided the first post-launch validation data for the NASA SeaWiFS satellite. Pigment data are used to characterise basin-scale variations in phytoplankton biomass and community composition over 100°of latitude, and to compliment the definition of hydrographic oceanic provinces. A summary of the key pigment characteristics of each province is presented. Concentrations of total chlorophyll a (totCHLa = chlorophyll a, CHLa + divinyl CHLa, dvCHLa) were greatest in high latitude temperate waters (>37°N and >35°S), and in the Canary Current Upwelling system. In these regions, the total carotenoid (totCAR) budget was dominated by photosynthetic carotenoids (PSCs). High accessory pigment diversity was observed of which fucoxanthin (FUC), 19'-hexanoyloxyfucoxanthin (HEX), and diadinoxanthin (DIAD) were most abundant, indicating proliferation of large eukaryotes and nanoflagellates. In contrast, tropical and sub-tropical waters exhibited concentrations of totCHLa below 500 ng l-1, with the North Atlantic Sub-tropical East gyre (NASE, 26.7-35°N), South Equatorial Current (SeqC, 7-14.6°S) and South Atlantic tropical Gyre (SATG, 14.6-26°S) characterised by totCHLa of <100 ng-1. These waters exhibited relatively limited pigment diversity, and the totCAR budget was dominated by photoprotecting pigments (PPCs) of which zeaxanthin (ZEA), a marker of prokaryotes (cyanobacteria and prochlorophytes), was most abundant. DvCHLa, a marker of prochlorophytes was detected in waters at temperatures >15°C, and between the extremes of 48°N and 42°S. DvCHLa accounted for up to two-thirds of totCHLa in oligotrophic provinces demonstrating the importance of prochlorophytes to oceanic biomass. Overall, HEX was the dominant PSC, contributing up to 75% of totCAR. HEX...
Haynes, D, Ralph, PJ, Prange, J & Dennison, B 2000, 'The Impact of the Herbicide Diuron on Photosynthesis in Three Species of Tropical Seagrass', Marine Pollution Bulletin, vol. 41, no. 0, pp. 288-293.
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The impact and recovery from exposure to the herbicide diuron [DCMU; 3-(30,40-dichlorophenyl)-1,1-dimethyl- urea] was assessed for three tropical seagrasses, maintained in outdoor aquaria over a 10-day period. Photosynthetic stress was detected using chlorophyll a Puorescence, measured with a Diving-PAM (pulse am- plitude modulated Puorometer). Exposure to 10 and 100 lg ly1 diuron resulted in a decline in eective quantum yield (F=Fm0 ) within 2 h of herbicide exposure in Cy- modocea serrulata, Halophila ovalis and Zostera capri- corni. Eective quantum yield also declined over the Rrst 24 h of exposure in H. ovalis at even lower diuron con- centrations (0.1 and 1.0 lg ly1). Eective quantum yield in H. ovalis and Z. capricorni was signiRcantly depressed at all diuron concentrations (0.1}100 lg ly1) after 5 days exposure, whereas eective quantum yield in C. serrulata was only signiRcantly lower in plants exposed to highest diuron concentrations (10 and 100 lg ly1). Eective quantum yield depression was present 5 days after plants exposed to 10 and 100 lg ly1 diuron were returned to fresh seawater. These results indicate that exposure to herbicide concentrations present in nearshore Queensland sediments present a potential risk to seagrass functioning.
Kohler-Rink, S & Kuhl, M 2000, 'Microsensor studies of photosynthesis and respiration in larger symbiotic foraminifera. I The physico-chemical microenvironment of Marginopora vertebralis, Amphistegina lobifera and Amphisorus hemprichii', Marine Biology, vol. 137, pp. 473-486.
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Kuhl, M & Fenchel, T 2000, 'Bio-optical characteristics and the vertical distribution of photosynthetic pigments and photosynthesis in an artificial cyanobacterial mat', Microbial Ecology, vol. 40, pp. 94-103.
O'Meara, T, Tovey, ER, Taylor, DJM, Graham, AH, Lovborg, U, Jones, AS & Sporik, R 2000, 'A New Immunodiagnostic System', Aerobiologia, vol. 16, pp. 113-118.
Ralph, PJ 2000, 'Herbicide Toxicity of Halophila ovalis Assessed by Chlorophyll a Fluorescence', Aquatic Botany, vol. 66, pp. 141-152.
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Razmovski, V, O’Meara, TJ, Taylor, DJM & Tovey, ER 2000, 'A new method for simultaneous immunodetection and morphologic identification of individual sources of pollen allergens', Journal of Allergy and Clinical Immunology, vol. 105, no. 4, pp. 725-731.
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Salih, A, Larkum, A, Cox, G, Kuhl, M & Hoegh-Guldberg, O 2000, 'Fluorescent pigments in corals are photoprotective', Nature, vol. 408, pp. 850-853.
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All reef-forming corals depend on the photosynthesis performed by their algal symbiont, and such corals are therefore restricted to the photic zone. The intensity of light in this zone declines over several orders of magnitudefrom high and damaging levels at the surface to extreme shade conditions at the lower limit1. The ability of corals to tolerate this range implies effective mechanisms for light acclimation and adaptation2. Here we show that the fluorescent pigments3, 4, 5, 6, 7, 8, 9 (FPs) of corals provide a photobiological system for regulating the light environment of coral host tissue. Previous studies have suggested that under low light, FPs may enhance light availability4, 5. We now report that in excessive sunlight FPs are photoprotective; they achieve this by dissipating excess energy at wavelengths of low photosynthetic activity, as well as by reflecting of visible and infrared light by FP-containing chromatophores. We also show that FPs enhance the resistance to mass bleaching of corals during periods of heat stress, which has implications for the effect of environmental stress on the diversity of reef-building corals, such as enhanced survival of a broad range of corals allowing maintenance of habitat diversity.
Thar, R, Blackburn, N & Kuhl, M 2000, 'A new system for three-dimensional tracking of motile microorganisms', Applied and Environmental Microbiology, vol. 66, no. 5, pp. 2238-2242.
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A new three-dimensional (3D)-tracking system with optimized dark-field illumination is presented. It allows simultaneous 3D tracking of several free-swimming microorganisms with diameters of >10 µm. Resolution limits and illumination efficiencies for different size classes of microorganisms are treated analytically. First applications for 3D tracking of protists are demonstrated.
Wieland, A & Kuhl, M 2000, 'Irradiance and temperature regulation of oxygenic photosynthesis and O2 consumption in a hypersaline cyanobacterial mat (Solar Lake, Egypt)', Marine Biology, vol. 137, pp. 71-85.
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Wieland, A & Kuhl, M 2000, 'Short-term temperature effects on oxygen and sulfide cycling in a hypersaline cyanobacterial mat (Solar Lake, Egypt)', Marine Ecology Progress Series, vol. 196, pp. 87-102.
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Ajani, P, Lee, R, Pritchard, T & Krogh, M 2000, 'Phytoplankton dynamics at a long term coastal station off Sydney, Australia (Poster Presentation). Harmful Algal Bloom Conference 2000, Hobart Australia.', Phytoplankton dynamics at a long term coastal station off Sydney, Australia. P.
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Poster Presentation
Mitchell, JG & Seymour, JR 2000, 'Water column microscale patchiness: Meeting of the tactic and turbulent length scales', Denmark.
Seymour, JR 2001, 'Spatial heterogeneity in bacterioplankton abundance', Australia.
Seymour, JR, Mitchell, JG & Waters, R 2000, 'Flow cytometric analysis allows for the measurement of marine microorganisms.', Australia.
Seymour, JR, Mitchell, JG, Waters, R & Pile, A 2000, 'High resolution small-scale sampling and flow cytometric analysis allows for the measurement of microdistributions of marine microorganisms', Australia.
Waters, R, Mitchell, JG, Seymour, JR & Pile, A 2000, 'The use of flow cytometry to characterise the marine planktonic microenvironment', Adelaide, Australia.