Functional bacterial and archaeal community structures of major trophic groups in a full-scale anaerobic sludge digester

Functional Bacteria and Archaea community structures of a full-scale anaerobic sludge digester were investigated by using a full-cycle 16S rRNA approach followed by microautoradiography (MAR)-fluorescent in situ hybridization (FISH) technique and micromanipulation. FISH analysis with a comprehensive set of 16S and 23S rRNA-targeted oligonucleoticle probes based on 16S rRNA clone libraries revealed that the Gram-positive bacteria represented by probe HGC69A-hybridized Actinobacteria (8.5 +/- 1.4% of total 4', 6-diamidino-2-phenylindole (DAPI)-stained cells) and probe LGC354-hybridized Firmicutes (3.8 +/- 0.8%) were the major phylogenetic bacterial phyla, followed by Bacteroidetes (4.0 +/- 1.2%) and Chloroflexi (3.7 +/- 0.8%). The probe MX825-hybridized Methanosaeta (7.6 +/- 0.8%) was the most abundant archaeal group, followed by Methanomicrobiales (2.8 +/- 0.6%) and Methanobacteriaceae (2.7 +/- 0.4%). The functional community structures (diversity and relative abundance) of major trophic groups were quantitatively analyzed by MAR-FISH. The results revealed that glucose-degrading microbial community had higher abundance (ca. 10.6 +/- 4.9% of total DAPI-stained cells) and diversity (at least seven phylogenetic groups) as compared with fatty acid-utilizing microbial communities, which were more specialized to a few phylogenetic groups. Despite the dominance of Betaproteobacteria, members of Chloroflexi, Smithella, Syntrophomonas and Methanosaeta groups dominated the [C-14]glucose-, [C-14]propionate-, [C-14]butyrate- and [C-14]acetate-utilizing microorganism community, and accounted for 27.7 +/- 4.3%, 29.6 +/- 7.0%, 34.5 +/- 7.6% and 18.2 +/- 9.5%, respectively. In spite of low abundance (ca. 1%), the hitherto unknown metabolic functions of Spirochaeta and candidate phylum of TM7 as well as Synergistes were found to be glucose and acetate utilization, respectively. (c) 2007 Elsevier Ltd. All rights reserved.