Fall 2007 Seminar Series

Symbiosis among unicells has been recognized for over a 100 years, but is it an oddity or is it important in the ocean? Ectosymbioses, endosymbioses, kleptoplastidy, and difficult to describe in-between relationships are common among microbes in the sea. These relationships are involved in autotrophy in "heterotrophic" lineages, metabolic adaptations of protists to anaerobic and sub-oxic habitats, and nitrogen fixation. The adaptive value of many common symbiotic relationships is unknown. As an aggregate, these relationships are not "oddities", but often the rule. Endosymbiosis, and perhaps organelle retention, are recognized as mechanisms of past and probably continuing eukaryotic cellular evolution in the sea. However the over-all significance of these relationships in tropho-dynamics and biogeochemistry is often under-recognized because of the great biodiversity of marine protists.  This presentation will focus on relationships, and their importance, that give "heterotrophic" cells the capacity for photosynthesis. Re-evaluation of symbioses/organelle retention with new tools and genomic approaches will hopefully provide a greater understanding of the adaptations and inter-dependencies of marine microbes and their quantitative significance.