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Project Progress

We participated in two Mixed Microbial Ecogenomics Focus Group field trips in 2001 (June and October) to the Guerrero Negro evaporation ponds. This collaborative project involves geochemical and molecular biological analysis of the microbial mat populations in these ponds. These mat populations are visually homogeneous over kilometers of extent, and they display steep geochemical gradients (e.g. light, oxygen) with depth. Core samples of microbial mats were frozen and returned for molecular analysis. DNA was subsequently extracted from these samples for use in two main projects investigating microbial diversity in these samples.

In the first, we are measuring the distribution and diversity of bacteria in these microbial mat samples. We used standard polymerase chain reaction (PCR) techniques to amplify the conserved bacterial 16S rRNA gene. We are assessing bacterial diversity using terminal restriction fragment length polymorphisms (T-RFLP), a rapid method for determining total community structure and composition. We have assessed diversity over two scales: horizontally, at varying spatial scales over a kilometer distance, and vertically, using cores sliced at submillimetric scales with depth. Results indicate that bacterial communities are remarkably stable across even large spatial scales (~1 km); however variation at even fine scale (cm) was detected. Significant variation in community structure was also observed with depth.

The second project is investigating a specific group of microorganisms, the sulfate-respiring prokaryotes. High levels of activity for this group have been measured in this site. In collaboration with Dr. Mitchell Sogin at Woods Hole MBL, we are determining the DNA sequence diversity of genes specific to this group with depth in the microbial mat samples.