Analysis of bacterial community in membrane-separation bioreactors by fluorescent in situ hybridization (FISH) and denaturing gradient gel electrophoresis (DGGE) techniques

Abstract

The bacterial communities of membrane-separation bioreactors (MBR) fed with raw sewage were analyzed by a pilot scale study. The community was analyzed by both Fluorescent in Situ Hybridization (FISH) and PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis) techniques. Five rRNA targeted group specific oligonucleotide probes showed that the alpha- and beta- subclasses of proteobacteria were the most dominant groups among them. The identification of ammonia-oxidizing bacteria in MBR was confirmed by three probes: NEU, Nsv 443 and Nso 190. Mostly the ammonia-oxidizers were found in groups and present in the form of clusters or aggregates. The ratio of NEU/EUB was estimated by double hybridization and image analysis techniques as 6%. The Nitrobacter sp. was also identified inside the MBR with the help of a NIT3 probe and they were also found to be present in the form of a cluster. Usually the clusters formed by the Nitrobacter sp. were smaller than those of ammonia-oxidizing groups. After numerical analysis on the band pattern of DGGE, it was found that the MBR bacterial communities were different from that of conventional activated sludge (CAS) communities with dissimilarity indexes more than 0.6. The diversity of the microbial community was estimated by the Shannon-Weaver index of general diversity. It was found that the value of the diversity index for the CAS process was 1.61 while those for two MBR processes were 1.68 and 1.59.

Microbial population analysis of nutrient removal-related organisms in membrane bioreactors

“…Nitrobacter sp. was not identified in any MBR samples, which is consistent with previous findings (Wagner and Loy 2002;Kraume et al 2005;Li et al 2005;Manser et al 2005), although Luxmy et al (2000) reported bright signal detection with the NIT3 FISH probe. The only NOB cells detected in this study belonged to the genus Nitrospira, described in the literature as an active contributor to nitrite oxidation (Kraume et al 2005;Li et al 2005;Manser et al 2005;Nielsen et al 2009).…”

“…not available a Recirculation between the membrane and biological tanks abundance than the Alphaproteobacteria (Table 4). Overall, the general community characteristics in the studied plants were similar to previously reported studies on MBRs, with Betaproteobacteria as the most abundant group (Luxmy et al 2000;Witzig et al 2002;Sofia et al 2004), followed by Gammaproteobacteria (Sofia et al 2004). Archaea were detected in all of the MBRs except in MBRs 5 and 7, but in low abundance.…”

“…Low or non-detection of AOB fluorescence signal was previously reported for MBR biomass (Luxmy et al 2000;Witzig et al 2002;Pala et al 2008). AOBs were present in the form of small coccobacilli and always grouped in small-sized clusters, although in MBR 3 it was also possible to observe some big AOB cocci dispersed in the flocs.…”

“…A few studies have compared the microbial community between MBR and CAS operated in parallel, and all revealed significant differences between the overall community structures (Luxmy et al 2000;Hall et al 2010;Wan et al 2011). MBRs seem to select a more stable microbial community as compared to CAS systems, where higher dynamics were observed (Hall et al 2010;Wan et al 2011).…”

Ecophysiology of nitrifying communities in membrane bioreactors

“…There have been contradictory reports on community structure of CAS and MBRs. Luxmy et al (2000) based on a denaturing gradient gel electrophoresis (DGGE) analysis reported significant difference in the nitrifying community structures of conventional activated sludge system compared with pilot-scale MBR, while Manser et al (2005) observed only a minor difference in the nitrifying community structures of MBR and CAS studied. However, a higher AOB and NOB fraction (7.19 %) of the total bacteria was reported in MBRs compared to the CAS (Zhang et al 2011b).…”