N-132. Microbial Diversity of Volcanic Hot Springs of the Lesser Antilles, St. Lucia, W.I.

L. M. Stout1, R. E. Blake1, J. P. Greenwood2, A. M. Martini3, E. Rose1;
1Yale Univ., New Haven, CT, 2Wesleyan Univ., Middletown, CT, 3Amherst Coll., Amherst, MA.

Background: The volcanic Sulphur Springs of Soufriere, St. Lucia, Lesser Antilles, present an extreme environment due to high temperatures, low pH values, and high concentrations of sulfate and boron. While hot spring microbial communities have been extensively studied elsewhere, microbial diversity at St. Lucia has not yet been described. This site offers unique geochemical characteristics, including large elemental variations between pools. We hypothesize that these geochemical characteristics shape the microbial communities here. Methods: We chose five pools representing the full range of geochemical characteristics found at the Sulphur Springs using 16S rRNA gene analysis. Water samples were filtered on-site and were frozen for later analysis. Analysis included DNA extraction from filters, PCR amplification of 16S rRNA genes from Bacteria and Archaea, clone library construction, and DNA sequencing of clones. Water samples were analyzed by ICP-OES and ion chromatography for elemental chemistry. Statistical methods including correlations between microbial diversity and water chemistry were conducted. Results: Water chemistry measurements revealed extremely high levels of sulfate and boron at several pools. Clone library analyses revealed that overall, microbial diversity at each pool was very low, with Hydrogenobacter dominating Bacterial communities at several pools except one site with low pH and low boron concentrations, dominated by Acidithiobacillus spp. The Archaeal component of all pools was almost exclusively Acidianus spp. In the pool with the highest boron and sulfate concentrations, only Archaeal sequences were detected. Conclusions: We saw large variations between sites with regard to boron concentrations (between 3 and 3500 mg/l) and pH values (2 to 7). Sulfate concentrations were high at all sites (between 1100 and 6200 mg/l). Interestingly, these pools contain some of the highest measured boron concentrations in the world. Few studies so far have related microbial community composition to boron concentrations. The extremely high boron concentrations may be one factor restricting microbial diversity here.