Bacterial populations and processes involved in acetate and propionate consumption in anoxic brackish sediment

Bacterial populations and pathways involved in acetate and propionate consu mption were studied in anoxic brackish sediment from the Grosser Jasmunder Bodden, German Baltic Sea. Uptake of acetate and propionate from the porewa ter was studied using stable carbon isotope-labeled compounds. Labeled acet ate was not produced as an intermediate during propionate uptake experiment s, and propionate consumption was not affected by the addition of acetate. In parallel, incorporation of labeled acetate and propionate into phospholi pid-derived Fatty acids (PLFA) was studied to indicate bacterial population s involved in the consumption of these substrates. The C-13-acetate label w as mainly recovered in even-numbered PLFA (16:1 omega 7c, 16:0 and 18:1 ome ga 7c). In contrast, primarily odd-numbered PLFA (a15:0, 15:0, 17:1 omega6 and 17:0) and the even-numbered i16:0 were labeled after incubation with C- 13-propionate. Although single PLFA labeled with propionate are commonly fo und in sulfate reducers, the complete PLFA-labeling pattern does not resemb le any of the know strains. However, the acetate-labeling pattern is simila r to Desuflotomaculum acetoxidans and Desulfofrigus spp., two acetate-consu ming, sulfate reducers. In conclusion, our data suggest that acetate and pr opionate were predominantly consumed by different, specialized groups of su lfate-reducing bacteria. (C) 2001 Federation of European Microbiological So cieties. Published by Elsevier Science B.V. All rights reserved.