Profiling bulking and foaming bacteria in activated sludge by high throughput sequencing.

Bulking and foaming bacteria (BFB) are notorious in wastewater treatment although they are always presented in the normal activated sludge and playing certain roles other than being harmful. Previous studies using microscopy or conventional molecular methods could hardly get the full profile of the BFB in the normal activated sludge. In this study, high throughput sequencing was adopted to investigate the BFB community, which was sub-dominant in activated sludge from 14 global wastewater treatment plants. The full-length 16S rRNA gene sequences of BFB groups were collected from previous studies to build a database for local BLAST and subsequent taxonomic assignment. The total BFB percentage in each sample ranged from 1.86% to 8.99% according to the 16S rRNA gene V4 pyrotags detected at the BLAST similarity cutoff of 97%. The most abundant and frequent BFB groups are 'Nostocoida limicola' I and II, Mycobacterium fortuitum, Type 1863, and 'Microthrix parvicella'. The BFB among the activated sludge samples were both biogeographically and technological distributed to some extent. An extending application was performed to evaluate and design oligonucleotides probes based on the rich information of high similar sequences. Our study also gave an exemplified case of investigation on the specific sub-dominant functional groups in complex bacterial communities revealed by high throughput sequencing. Crown