BACTERIAL ABUNDANCE AND DIVERSITY IN THE BARBADOS-TRENCH DETERMINED BY PHOSPHOLIPID ANALYSIS

The Barbados trench is characterized by large fields of volcanoes and mounds located over a distance of 30 km above the northern slope of a basement ridge corresponding to an inactive transform fault. Sediments from various locations were collected and analyzed for their lipid co ntents, Bacterial input to the overall biomass was estimated through t he analysis of phospholipid ester-linked fatty acid (PLFA) profiles an d glycerol ether lipids. Results indicated a eubacterial biomass estim ated to be 10(9) cells (g dry wt)(-1). Individual fatty acid profiles revealed the presence of sulfur-oxidizing bacteria common to many deep -sea sites but also a large contribution of type I and type II methano trophs to the eubacterial biomass. The presence of methanotrophs was f urther supported by the analysis of specific biomarkers of these micro organisms as well as some unusual trans fatty acid isomers. Anaerobic bacteria and presumably sulfate reducing bacteria were also present, a s well as archaebacteria and primarily methanogens, as indicated by gl ycerol ether lipid analysis.