Phylogenetic analysis of bacterial communities in mesophilic and thermophilic bioreactors treating pharmaceutical wastewater

phylogenetic diversity of the bacterial communities supported by a seven-st age, full-scale biological wastewater treatment plant was studied. These re actors were operated at both mesophilic (28 to 32 degrees C) and thermophil ic (50 to 58 degrees C) temperatures. Community fingerprint analysis by den aturing gradient gel electrophoresis (DGGE) of the PCR-amplified V3 region of the 16S rRNA gene from the domain Bacteria revealed that these seven rea ctors supported three distinct microbial communities. A band-counting analy sis of the PCR-DGGE results suggested that elevated reactor temperatures co rresponded with reduced species richness. Cloning of nearly complete 16S rR NA genes also suggested a reduced species richness in the thermophilic reac tors by comparing the number of clones with different nucleotide inserts ve rsus the total number of clones screened. While these results imply that el evated temperature can reduce species richness, other factors also could ha ve impacted the number of populations that were detected. Nearly complete 1 6S rDNA sequence analysis showed that the thermophilic reactors mere domina ted by members from the beta subdivision of the division Proteobacteria (be ta-proteobacteria) in addition to anaerobic phylotypes from the low-G+C gra m-positive and Synergistes divisions. The mesophilic reactors, however, inc luded at least six bacterial divisions, including Cytophaga-Flavobacterium- Bacteroides, Synergistes, Planctolmycetes, low-G+C gram-positives, Holophag a-Acido-bacterium, and Proteobacteria (alpha-proteobacteria, beta-proteobac teria, gamma-proteobacteria and delta-proteobacteria subdivisions). The two PCR-based techniques detected the presence of similar bacterial population s hut failed to coincide on the relative distribution of these phylotypes, This suggested that at least one of these methods is insufficiently quantit ative to determine total community biodiversity-a function of both the tota l number of species present (richness) and their relative distribution (eve nness).