Methanogenic archaeal community in the sediment of an artificially partitioned acidic bog lake

The methanogenic archaeal communities in the sediment of two basins of an artificially partitioned acidic bog lake were studied. In the northeast basin, which was separated from a peat bog, a high methane production rate was measured only in the upper layers of the sediment. In contrast, methane production was detected at various depths of the sediment in the southwest basin, which continuously receiving humic acids from the bog. Ten bands were observed in the denaturing gradient gel electrophoresis (DGGE) fingerprint of the 16S rDNA archaeal amplicons from the NE basin top (0-5 cm) sediment layer, which reflected the presence of at least 10 ribotypes. Seventy clones of the 16S rDNA amplicons were obtained from the NE basin top sediment layer, and were grouped into 10 operational taxonomy units (OTUs) according to their positions on the DGGE gel. Seven of these OTUs could be matched with the bands of the community fingerprint. Phylogenctic analyses indicated that the sequences clustered into three groups: five of the OTUs were related to Methanosaeta, four OTUs to Methanomicrobiales and one OTU to Methanobacterium. Among the OTUs, sequences with high similarities (> 96%) were retrieved. The sequence data suggested that the diversity of the methanogenic archaeal community was limited. Bands corresponding to those three phylogenetic groups were found in the DGGE fingerprints of both NE and SW basins, which reflected the presence of the same dominant methanogenic archaeal groups in both basins. However, differences in the distribution of the ribotypes that had high 16S rRNA sequence identities were observed in the fingerprints between the two basins at various depths. The microdiversity decreased along the sediment depth in the NE basin, and vice versa in the SW basin. The greater variety of the archaeal ribotypes, apparently, correlated with the higher methanogenesis rate. (C) 2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.