Full-cycle rRNA approach-based method for estimating bacterial diversity in an industrial activated sludge.

FIGUEROLA, EVA LM; ERIJMAN, LEONARDO

Viena, Austria

Congreso; 11th International Symposium on Microbial Ecology ISME-11; 2006

International Society for Microbial Ecology

Most parametric and nonparametric methods currently applied to estimate microbial diversity, derive the numbers of individuals for each operational taxonomic units (OTU) from the frequency of the clones in 16S rDNA gene libraries. Therefore, they are subjected to a number of PCR biases. In this work, the diversity of bacterial populations present in an industrial activated sludge, was estimated by fitting the data of the full-cycle rRNA approach to a model of abundance distribution. Samples were obtained from a full-scale activated sludge plant receiving pre-treated wastewater of an oil refinery. A library of 16s rDNA was constructed, and 139 sequences were assigned to OTUs by the DOTUR program, using a genetic distance level between sequences of 0.05. A group of 17 newly designed rRNA-targeted oligonucleotide probes were used to quantify OTUs represented with more than two clones in the library, by fluorescence in situ hybridization. FISH counts were transformed and fitted to normal distribution to get 95% confidence limits. The data was best described by a geometric distribution of OTUs, after the goodness of fit was evaluated by the Kolmogorov- Smirnov test. According to the model, a minimum 102 bacterial species are present per mL of activated sludge. In conclusion, a PCR-independent description of the distribution of dominant bacteria in industrial activated sludge was obtained. The geometric character of the abundance distribution of species might reflect a niche-oriented structure, where resource competition drives the structuring of the bacterial community.