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USE OF PHOSPHOLIPID FATTY ACID PROFILES TO STUDY THE MICROBIAL COMPOSITION OF CYANOBACTERIAL MATS IN CABO ROJO SOLAR SALTERNS
Citation:
Gonzalez, M. L., L. Casillas, AND M Molina. USE OF PHOSPHOLIPID FATTY ACID PROFILES TO STUDY THE MICROBIAL COMPOSITION OF CYANOBACTERIAL MATS IN CABO ROJO SOLAR SALTERNS. Presented at Annual Biomedical Research Conference for Minority Students, San Diego, CA, October 15-18, 2003.
Impact/Purpose:
The overall objective of this task is to develop quantitative relationships for assessing the vulnerability of aquatic resources to global change. The task will contribute experimental and modeling tools for assessments of the interactions of global climate and UV changes with coral reefs and selected watersheds and estuaries in the U.S. These activities are contributing primarily to two APGs in the ecosystems component of the Global Change Research Multiyear Plan: the 2006 APG (APG 3) on building the capacity to assess global change impacts on coastal aquatic ecosystems, including coral reefs and estuaries and the 2004 APG (APG 2) on building capacity to assess and respond to global change impacts on selected watersheds. One major task objective is to assess interactions of global warming and UV exposure that are contributing to the observed coral bleaching and disease. Our lab is working with scientists at the NHEERL Gulf Ecology Lab to characterize UV exposure and effects at several coral reef sites. Other research in this task is examining the interactions between UV-induced breakdown of refractory organic matter in estuaries and coastal areas that enhance UV penetration into the water and concurrently form biologically-labile nitrogen-, phosphorus- and carbon-containing substances that stimulate productivity and microbial activity. This task also involves research in central Brazil that is part of the Large Scale Biosphere Atmosphere Experiment (LBA). The objectives of this project are to assess the impacts of land use and climatic changes on soil nutrient cycles and microbiota, trace gas exchange and water quality in the Brazilian cerrado. This work involves a close collaboration between EPA and a group of scientists from the Department of Ecology, University of Brasilia, Brazil. Other objectives of this task are to assess the interactions of land use and climate changes with the ecological functioning of streams in watersheds of the Piedmont region of the southestern U.S.
Description:
The Cabo Rojo Saltern located in the West side of Puerto Rico is a hypersaline ecosystem that consists of crystallizer ponds surrounded by series of cyanobacterial mats. Although this ecosystem harbors a variety of microorganisms not much is known about their identity and relative abundance. We are particularly interested in how these microbial communities are affected by seasonal changes in the site. To determine the relative abundance of archaeal populations within the ponds and mats of the salterns we have implemented a method to detect archaeal lipids. Two peaks depicting lipids with 23 and 25 carbons and an isoprenoid structure characteristic of archaeabacteria were found in samples collected from the mats during dry and wet seasons. No signals were detected in water samples collected from the ponds, presumably due to low cell yield. We have also generated fatty acids methyl ester (FAME) profiles during the dry and rainy season. The most abundant peaks in the FAME profiles from the microbial mats during the wet season correspond to 18:1 w7c fatty, characteristic of Gram-positive bacteria. We also found iso15:0, common in Gram-positive bacteria, cy19:0 characteristic of anaerobic bacteria, 10me16:0 common among Actinomycetales and some sulfate reducing bacteria, such as Desulfobacter sp, and br 14:0 characteristic of gram positive bacteria. During the dry season, we found basically the same lipids, with the exception of 16:1w7c (a Gram negative indicator) and 18:0 (general indicator). FAME analyses performed on some of the bacterial isolates cultured from the salterns indicated that eleven of our isolates have very little similarity to previously identified bacteria. Our next step is to identify cultured bacteria using phylogenetic analysis to determine whether novel extreme halophiles are common inhabitants of the Cabo Rojo salterns.