Analysis of bacterial community in bulking sludge using culture-dependent and -independent approaches

The bacterial community of a bulking sludge from a municipal wastewater treatment plant with anoxic-anaerobic-oxic process was investigated by combination of cultivation and 16S rRNA gene clone library analysis for understanding the causes of bulking.A total of 28 species were obtained from 63 isolates collected from six culture media.The most cultivable species belonged to γ-Proteobacteria including Klebsiella sp.,Pseudomonas sp.,Aeromonas sp.and Acinetobacter sp.Further analysis of these strains by repetitive sequence based on polymerase chain reaction （rep-PCR） technology showed that rep-PCR yielded discriminatory banding patterns within the same genus using REP and BOX primer sets.While the culture-independent assessment revealed that β-Proteobacteria was the dominant group in the bulking sample.Sequence analysis revealed that the highest proportion （14.7%） of operational taxonomic units was 98% similar to Candidatus Accumulibacter phosphatis,which is used to remove phosphorous from wastewater.Our results indicated that combining different approaches can produce complementary information,thus generate a more accurate view of microbial community in bulking sludge.