Bacterial diversity and community composition in the chemocline of the meromictic alpine Lake Cadagno as revealed by 16S rDNA analysis

Using different techniques of molecular biology we investigated the bacteri al diversity of the chemocline of the meromictic Lake Cadagno. Cloning of a total community 16S rDNA PCR product and subsequent screening with a combi nation of amplified ribosomal DNA restriction analysis and temporal tempera ture gradient gel electrophoresis (TTGE) analysis revealed that 30 of 47 ra ndomly selected clones were unique. Partial sequencing and comparative anal ysis indicated a high bacterial diversity dominated by the gamma-Proteobact eria (33.3%). Most of these rDNA clone sequences were not closely related t o any 16S rDNA sequence in the database. In a second approach. the TTGE pat tern from an environmental sample was compared with the migration of the cl oned 16S rDNA fragments. Four clone types were identified on the environmen tal pattern by excising and sequencing comigrating bands, three of which we re well represented in the library: two Chromatiaceae species and one seque nce affiliated with the Desulfobulbus assemblage. Using the fluorescent in situ hybridization technique we essentially confirmed the results of the cl oning experiments and the TTGE analysis. (C) 2000 Federation of European Mi crobiological Societies. Published by Elsevier Science B.V. All rights rese rved.