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Project Progress

Protist diversity in extreme environments (dm)

Natural microbial communities living at the limits of physiological tolerance in extreme environments exist in a variety of marine ecosystems. There has been speculation that some of these environments are similar to physiochemical conditions of primitive Earth or to conditions that are (or were) present on other planets and moons. Thus, studies of microorganisms from extreme environments on Earth may provide insight into early evolutionary events.

Our research on the microbial eukaryotic diversity in extreme environments employs both traditional culture techniques and culture-independent molecular methods. This past year our project has focused on the analysis of deep-sea sediments from the Antarctic. We chose to work with these samples because they can provide a complementary picture to the protistan diversity studies at hydrothermal sites. The non-hydrothermal deep-sea tends to be sparsely populated, but is certainly not sterile. The microbial (both prokaryotic and eukaryotic) populations in these areas potentially harbor organisms with different growth strategies. There has been very little work on the microbial populations in this area, an ecosystem that may share characteristics with the deep ocean floor of Europa.

We have been pursuing denaturing gradient gel electrophoresis (DGGE) analysis of the protistan community from the deep-sea sediment samples that we collected from a previous Antarctic cruise. It has been very difficult to obtain good banding patterns for these samples, but we have been optimizing our PCR amplification parameters with some success.

In addition to direct genetic analyses, we have recovered protistan cultures from these sediments. Most of our cultures are ameboid protists, but we have also recovered small flagellates and small choanoflagellates. We are planning to compare small subunit ribosomal gene identification of these cultures with ribosomal sequences that we (eventually) recover directly from the sediments to determine whether these cultured protists might be representative of organisms originally in the samples.