MOLECULAR MICROBIAL DIVERSITY OF AN ANAEROBIC DIGESTER AS DETERMINED BY SMALL-SUBUNIT RDNA SEQUENCE-ANALYSIS

The bacterial community structure of a fluidized-bed reactor fed by vi nasses (wine distillation waste) was analyzed, After PCR amplification , four small-subunit (SSU) rDNA clone libraries of Bacteria, Archaea, Procarya, and Eucarya populations were established, The community stru cture was determined by operational taxonomic unit (OTU) phylogenetic analyses of 579 partial rDNA sequences (about 500 bp long), A total of 146 OTUs were found, comprising 133, 6, and 7 from the Bacteria, Arch aea, and Eucarya domains, respectively, A total of 117 bacterial OTUs were affiliated with major phyla: low-G+C gram-positive bacteria, Cyto phaga-Flexibacter-Bacteroides, Proteobacteria, high-G+C gram-positive bacteria, and Spirochaetes, where the clone distribution was 34, 26, 1 7, 6, and 4%, respectively, The other 16 bacterial OTUs represent 13% of the clones, They were either affiliated with narrow phyla such as P lanctomyces-Chlamydia, green nonsulfur bacteria, or Synergistes, or de eply branched on the phylogenetic tree, A large number of bacterial OT Us are not closely related to any other hitherto determined sequences, The most frequent bacterial OTU represents less than 5% of the total bacterial SSU rDNA sequences, However, the 20 more frequent bacterial OTUs describe at least 50% of these sequences, Three of the six Archae a OTUs correspond to 95% of the Archaea population and are very simila r to already known methanogenic species: Methanosarcina barkeri, Metha nosarcina frisius, and Methanobacterium formicicum, In contrast, the t hree other Archaea OTUs are unusual and are related to thermophilic mi croorganisms such as Cremarchaea or Thermoplasma spp. Five percent of the sequences analyzed were chimeras and were removed from the analysi s.