Estimating bacterial diversity in activated sludge from the full-cycle rRNA approach

FIGUEROLA, ELM; ERIJMAN, L

Pinamar, Buenos Aires, Argentina

Congreso; X Congreso Panamerican Association for Biochemistry and Molecular Biology; 2005

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB)

A novel strategy based on the full-cycle rRNA approach is proposed to describe the richness of bacterial populations present in activated sludge, circumventing the limitations of PCR-based analysis. DNA was isolated from sludge taken from the aeration basin of a full-scale industrial treatment plant receiving pretreated wastewater of an oil refinery. A total of 139 16S rRNA gene clones were sequenced for phylogenetic analysis and assigned to 46 OTUs. We have designed 20 rRNA-targeted oligonucleotide probes for quantitative FISH analysis, specific for OTUs represented by at least two clones in the library. 63 + 3 % of the DAPI-stained cells were accounted for by considering OTUs represented by more than four clones in the library, which belonged to the classes Alpha and Beta of the Proteobacteria, and to different members of the phylum Acidobacteria. Other bacteria in the sludge, determined using phylum-level probes were Actinobacteria, Verrucomicrobia, Bacteroidetes and Firmicutes, each one represented with a single clone in the library, and Deltaproteobacteria and Planctomycetes, for which representative clones were not found in the 16S rRNA gene clone library. Due to the limited amount of data, none of the species abundance models fit optimally the abundance distribution. However, using FISH data to fit species abundance models shows promise for estimating total richness, because it displays the actual distribution of bacterial populations in a sample.