DIVERSITY IN METHANE ENRICHMENTS FROM AGRICULTURAL SOIL REVEALED BY DGGE SEPARATION OF PCR AMPLIFIED 16S RDNA FRAGMENTS

Denaturing gradient gel electrophoresis (DGGE) profiles of PCR amplifi ed V3 regions of 16S rRNA genes were used to assess the diversity in e nrichment cultures with methane as the only carbon and energy source. The enrichments originated from two agricultural soils. One was a sand y soil with low (10%) organic content, the other an organic soil with approximately 50% organic content. DGGE provided a fast evaluation of the distribution of amplifiable sequence types indicating that specifi c bacterial populations had been enriched from each soil. The DGGE pro files revealed a broader range of amplified V3 fragments in the commun ity derived from organic soil than from sandy soil. Fragments from 19 individual DGGE bands were sequenced and compared with 27 previously p ublished 16S rRNA gene sequences. The sequences confirmed the high div ersity with the presence of different methylotrophic populations in ea ch enrichment. No affiliation was found with type I methanotrophs, ins tead type II methanotroph sequences were found in the enrichments from both soil types. Some of the fragments from the organic soil enrichme nt were not affiliated with methylotrophs. Most of the sequences clust ered distantly on a branch within the cr-Proteobacteria. These facts s uggested that previously undescribed methylotrophs are abundant in met hane enrichments from agricultural soil. (C) 1998 Federation of Europe an Microbiological Societies. Published by Elsevier Science B.V.