MICROBIAL COMMUNITY STRUCTURE IN THE SEDIMENTS OF HIROSHIMA BAY, JAPAN

The structure of the microbial community in sediments of Hiroshima Bay was determined using phospholipid ester-linked fatty acid-(PLFA) anal ysis. The major fatty acids of the 48 PLFA identified were 16:0, 16:1d 9c, i15:0, a15:0, 18:1d9c and 18:1d9t. Three clusters indicated differ ences in PLFA profiles of the sediments and relative proportions of PL FA were significantly different among the clusters. The total PLFA con centration and the calculated microbial biomass in the sediments colle cted in winter were lower than the values reported in other seasons. P LFA assigned to the different functional groups were used to examine t he relative dominance of the groups in the microbial community structu re. Aerobic prokaryotes and eukaryotes were the predominant groups, fo llowed by Gram-positive bacteria and other anaerobic bacteria, sulphat e-reducing bacteria and other anaerobic prokaryotes. The micro-eukaryo tes were the least dominant and a predominance of prokaryotes was indi cated. The physiological stress to which the micro-organisms were subj ected is discussed.