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Project Progress

No funding was received this year. The following sections report our progress on studies relevant to the aims of our NAI team. Funding sources were NSF, Merck Foundation and the Packard Foundation

Ms. Yundan Pi is characterizing the squalene-hopene cyclase (sqhC) gene diversity in a tropical hypersaline lake (Storr’s lake, Bahamas), temperate hypersaline lake (Mono Lake), highly euxinic stratified lake (Mahoney Lake), and a sample of desert cryptogamic crust from Moab, Utah. Preliminary results show there are sqhC sequences in desert crust from Cyanobacteria. Data from other sites are pending. Together with characterization of hopanoid lipids, these locations should provide a clearer picture of the aerobic (or anaerobic) prevalence of hopanoid biosynthesis.

Mr. William Leavitt and Mr. James Saenz have just finished a similar characterization of samples from across a land-sea gradient in the Bahamas (San Salvador Island). The manuscript from this work is nearly ready to be submitted. The work shows that hopanoid structural diversity and phylogenetic diversity is greatest in soil, lowest in the intermediate estuary, and higher again in the open ocean (but not as high as soils). The samples are dominated by bacteriohopanetetrol, 32,35-anhydrobacteriohopanetetrol, and hopaneribonolactone; and in the soil, additionally by adenosylhopane. The phylogeny indicates that unknown clades dominate in soil (although possibly many are relatives of Acidobacteria) and alpha-Proteobacteria or an unidentified phylum that is similar either to alpha-Proteobacteria or Actinomycetes dominates in the ocean.

Ann Pearson completed and submitted a paper co-authored with Douglas B. Rusch of the J. Craig Venter Insitute, analyzing all >13 gigabases of DNA available from the Global Ocean Sampling Expedition. The analysis was enabled by a customized version of the sequence fragment and analysis tool written by D.B. Rusch and specifically adapted for the research question of A. Pearson. The paper shows that alpha-Proteobacteria are the putative dominant source of environmental sqhC gene fragments in samples of marine origin, while other groups, including delta-Proteobacteria and Acidobacteria, are more important on land. This paper is submitted to ISME Journal.