Fermentative or anaerobic metabolism allows organisms that normally grow under oxic conditions to sustain themselves as levels of oxygen in the environment decline. Using genomic, transcriptomic, biochemical and physiological technologies, we are characterizing anaerobic energy metabolism in the soil-dwelling green alga Chlamydomonas reinhardtii (Chlamydomonas), which has become a model for elucidating a range of biological processes in photosynthetic protists. Chlamydomonas genes encoding proteins associated with multiple fermentation pathways have been identified and the regulation of those genes examined. The results suggest that Chlamydomonas fermentation is highly controlled, which is reflected by the flexible use of different branches of fermentation metabolism under conditions of limited access to other branches (e.g. in different mutant strains).
To date, little is known about the roles/advantages of the various branches of fermentation metabolism in Chlamydomonas, how photosynthetic eukaryotes sense changing environmental O2 levels, and the subsequent specific responses elicited; these responses appear to occur at both the transcriptional and post-transcriptional levels. We are approaching these issues using genomic, genetic, biochemical and physiological resources.
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