Diversity of the domain Archaea as determined by 16S rRNA gene analysis in the sediments of Lake Soyang

Abstract

Lake Soyang is a deep (maximum depth 100 m) meso-eutrophic lake in Korea. To identify members of the domain Archaea which inhabit such an environment, we used PCR amplification to construct a library of 16S rRNA genes (16S rDNAs) cloned from DNA extracted from the sediments of Lake Soyang. Oligonucleotides specific to conserved regions of archaeal 16S rDNA were used as primers for PCR amplification. Sequencing of the cloned 1.1 kb long fragments revealed extensive phylogenetic diversity of Archaea within this system. Forty clones were sequenced and a wide range of Euryarchaeta sequences were recovered, but no sequences from the orders Methanobacteriales, Methanococcales, or Crenarchaeota were recovered. Fourteen clones clustered with the order Methanosarcinales, and eleven of these were closely related to Methanosaeta, which only carry out aceticlastic methanogenesis. This group represented 27.5 % of all the methanogenic clones identified. The other twenty-six clones clustered with the order Methanomicrobiales which not only formed the larger proportion but are also highly methanogenic.