Poster: Heavy Metals
Abs #
101: Polyphophate metabolism in Chlamydomonas acidophila in phosphate-limited conditions under heavy metal (Cd) stress.
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Presenter: |
Nishikawa, Kahoko , kaho@jk9.so-net.ne.jp |
Authors | Nishikawa, Kahoko (A) Otomo, Ryo (B) Yamakoshi, Yoko (C) Tominaga, Noriko (A) | | Affiliations: |
(A): Institute of Environmental Science for Human Life, Ochanomizu University
(B): National Institute of Livestock and Grassland Science, Japan
(C): Division of Organic Chemistry, National Institute of Health Sciences, Japan
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This study is concerned with polyphosphate metabolism in an acidophilic unicellular green alga Chlamydomonas acidophila (Chlorophyceae). Algal intracellular polyphosphate levels can vary widely, depending on whether the alga is growing under phosphorus-limited conditions, phosphorus-sufficient conditions, or heavy metal (Cd) stress. The response and state of the intracellular polyphosphates in Chlamydomonas acidophila were studied using in vivo 31P-NMR and quantitative analysis. In phosphate-limited cells, polyphosphate degradation was first induced, followed by the depletion of intracellular phosphate levels. When these cells were transferred to phosphate sufficient medium, polyphosphate was synthesized intensively in a short time. Polyphosphates were observed by fluorescence microscopy in the cell using 4f, 6-diamidino-2-phenylindole. These results were consistent with 31P-NMR analysis and suggested that polyphosphate biosynthesis in C. acidophila was very sensitive to external phosphate conditions. On the other hand, Cd stress induced the expenditure of polyphosphate, as previously reported1). In an attempt to identify the degradation products of the polyphosphates, C. acidophila cells were labeled with 32P, and acid extracts analyzed by thin layer chromatography (TLC). This demonstrated that Cd stress induces the appearance of several new components, of which the major one was identified as low weight phosphates. Polyphosphate degradation seems to have an important role in the cell under crisis conditions.@Reference: 1) Ultrastructural changes in Chlamydomonas acidophila (Chlorophyta) induced by heavy metals and polyphophate metabolism. FEMS Microbiology Ecology (in press)
