Christen, G, Stevens, G, Lukins, PB, Renger, G & Larkum, AWD 1999, 'Isolation and characterisation of oxygen evolving thylakoids from the marine prokaryote Prochloron didemni', FEBS Letters, vol. 449, no. 2-3, pp. 264-268.
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The present study describes the first successful attempt to isolate oxygen evolving thylakoids and thylakoid fragments from the marine prokaryote Prochloron didemni, a member of the recently discovered group of prochlorophytes. Oxygen evolving thylakoid membranes and fragments were isolated from seawater suspended cells of Prochloron didemni by passage of the cells through a Yeda press and subsequent differential centrifugation of the broken material. Three fractions were collected at 1000×g, 5000×g, and 30 000×g and identified by light microscopy as cells (and their fragments), thylakoids and membrane fragments, respectively. Pigment content, oxygen evolution rate and 77 K fluorescence spectra of these fractions were virtually identical. This finding indicates that the membrane fragments obtained are not enriched in photosystem II. The P680+ reduction kinetics of thylakoid membrane fragments were determined by monitoring flash induced absorption changes at 830 nm and analysing the time course of their decay. The multiphasic relaxation kinetics and their modification by NH2OH were found to be similar to those observed in cyanobacteria and plants. These findings provide an independent line of evidence for the idea of a high conservation of the basic structural and functional pattern of the water oxidising complex in all organisms that perform oxygenic photosynthesis.
Doblin, MA, Blackburn, SI & Hallegraeff, GM 1999, 'Comparative study of selenium requirements of three phytoplankton species: Gymnodinium catenatum, Alexandrium minutum (Dinophyta) and Chaetoceros cf. tenuissimus (Bacillariophyta)', JOURNAL OF PLANKTON RESEARCH, vol. 21, no. 6, pp. 1153-1169.
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This study investigated the selenium (Se) requirements of three phytoplankton species which commonly bloom in southern Australian estuaries. The present study showed that the toxic dinoflagellate Gymnodinium catenatum Graham had an obligate requirement f
Doblin, MA, Blackburn, SI & Hallegraeff, GM 1999, 'Growth and biomass stimulation of the toxic dinoflagellate Gymnodinium catenatum (Graham) by dissolved organic substances', JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY, vol. 236, no. 1, pp. 33-47.
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Blooms of the toxic dinoflagellate Gymnodinium catenatum are annually recurrent events in south-east Tasmanian waters. Extensive blooms are preceded by a rainfall trigger and the associated influx of dissolved organic matter (DOM; otherwise known as humi
Helfrich, M, Ross, A, King, GC, Turner, AG & Larkum, AWD 1999, 'Identification of [8-vinyl]-protochlorophyllide a in phototrophic prokaryotes and algae: chemical and spectroscopic properties', Biochimica et Biophysica Acta (BBA) - Bioenergetics, vol. 1410, no. 3, pp. 262-272.
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[8-vinyl]-Protochlorophyllide a1 was isolated from a Prochloron sp. associated with the host ascidian, Lissoclinum patella. To obtain sufficient amounts for identification of the purified pigment, suitable extraction procedures and HPLC systems were developed. The structure was finally elucidated by UV-VIS and fluorescence spectroscopy, mass spectrometry and NMR (rotating-frame Overhauser enhancement spectroscopy). [8-vinyl]-Protochlorophyllide a was originally detected only as an intermediate in chlorophyll biosynthesis. Although its presence as a light-harvesting pigment was previously suggested in some prochlorophytes and eukaryotic algae, this is the first unequivocal demonstration of [8-vinyl]-protochlorophyllide a in an oxygenic phototroph. We also show that [8-vinyl]-protochlorophyllide a occurs in Prochloron species of four other ascidians as well as in Micromonas pusilla and Prochlorococcus marinus. The possible role of this pigment in photosynthesis is discussed. Copyright (C) 1999 Elsevier Science B.V.
Lockhart, PJ, Howe, CJ, Barbrook, AC, Larkum, A & Penny, D 1999, 'Spectral Analysis, Systematic Bias, and the Evolution of Chloroplasts', Molecular Biology and Evolution, vol. 16, no. 4, pp. 573-576.
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Ralph, PJ 1999, 'Light-induced photoinhibitory stress responses of laboratory-cultured Halophila ovalis', BOTANICA MARINA, vol. 42, no. 1, pp. 11-22.
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This paper details experiments performed to investigate the short-term stress effects of both high and low-light regimes on laboratory-cultured Halophila ovalis using chlorophyll fluorescence. Increasing irradiance up to 400 mu mol quanta m(-2) s(-1) on
Ralph, PJ 1999, 'Photosynthetic response of Halophila ovalis (R-Br.) Hook. f. to combined environmental stress', AQUATIC BOTANY, vol. 65, no. 1-4, pp. 83-96.
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Combinations of stresses showed an additive effect in comparison to the individual stress responses. It is apparent from these results that thermal, elevated-light or osmotic stress increases the sensitivity of Halophila ovalis to any of the other stress
Ralph, PJ, Gademann, R, Larkum, AWD & Schreiber, U 1999, 'In situ underwater measurements of photosynthetic activity of coral zooxanthellae and other reef-dwelling dinoflagellate endosymbionts', MARINE ECOLOGY PROGRESS SERIES, vol. 180, pp. 139-147.
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Chlorophyll fluorescence was used to assess the iu situ photosynthesis of a range of reef-dwelling endosymbionts. Such non-intrusive in situ measurements became possible after the recent development of a submersible pulse modulated fluorometer (DIVING-PA
Waters, R, Seymour, JR, Pearson, L, Nelson, C, Bass, L & Mitchell, JG 1970, 'The role of small-scale turbulence in structuring the biological microenvironment.', United States.
