Abstract

The microbial community composition and dominant bacterial populations in anoxic-oxic activated sludge from a full-scale wastewater treatment plant (WWTP), were investigated with polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) coupled with sequence analysis of 16S rRNA gene fragments from dominant bands. The bacterial ecological distribution at different parts of each reactor, the dynamics of the bacterial community structure over the total process course and temporal dynamics were obtained by comparing the DGGE patterns. Differences were noted between three sections of the reactors and also two reactors within the entire process of the system. Temporal variations in bacterial composition of the activated sludge in each reactor were responded to their circumstances. The prominent DGGE bands were excised and sequenced in order to identify the predominantly present and active bacterial populations. Here, combined with phylogenetic analysis of the DGGE fingerprints, the four major bacterial lineages can be revealed: α, β, γ- Proteobacteria, and the phylumFirmicutes (low G+C Gram-positive). The 16S rDNA sequence analysis indicated that the DGGE bands of dominant bacterial from this plant harbored sequences of possible nitrogen remover with potential aerobic denitrification / heterotrophic nitrification.

Key words: Community structure, PCR-DGGE, 16S ribosomal DNA, wastewater treatment plant (WWTP); activated sludge.

Abbreviation

Abbreviations: PCR, Polymerase chain reaction; DGGE, denaturing gradient gel electrophoresis; WWTP, wastewater treatment plant; SND, simultaneous nitrification and denitrification; EBPR, enhanced biological phosphate removal; T-RFLP, terminal restriction fragment length polymorphism; ARDRA, amplified ribosomal DNA restriction analysis; SBRs, sequencing batch reactors; TE, tris ethylene diamine tetraacetic acid; DO, dissolved oxygen; COD, chemically dissolved oxygen; HRT, hydraulic retention time; MLSS, mixed liquor suspended solid.