Effects of 3,5-dichlorophenol on excess biomass reduction and bacterial community dynamics in activated sludge as revealed by a polyphasic approach.
The effects of 3,5-dichlorophenol (DCP) on excess sludge reduction and microbial community dynamics were studied using laboratory-scale activated sludge reactors. The addition of 3,5-DCP at an interval of 7-8 days of operation resulted in effective reduction of growing biomass without a significant decrease in substrate removal activity. However, this uncoupling effect completely disappeared after 30 days of operation. Quinone profiling showed that a drastic component shift from ubiquinone-8 (Q-8) to Q-10 as the major homolog took place during this period of operation, suggesting that Q-10-containing bacteria, i.e., Alphaproteobacteria, became predominant at the uncoupler-ineffective stage. This result was supported by PCR-aided denaturating gradient gel electrophoresis and clone library analyses of 16S rRNA genes and fluorescence in situ hybridization. Among the gene clones detected, those corresponding to Brevundimonas predominated at the uncoupler-ineffective stage. The uncoupler-added reactor yielded 3,5-DCP-resistant Pseudomonas strains as the predominant cultivable bacteria and non-3,5-DCP-resistant Brevundimonas strains as the second most abundant isolates These results suggest that the disappearance of the uncoupling function of 3,5-DCP during the long-term operation of the reactor is related to the drastic community change with increasing populations of Alphaproteobacteria. Most of these alphaproteobacteria represented by Brevundimonas are not resistant to 3,5-DCP but, by an unknown mechanism, may support the bioprotection of the microbial community from the uncoupling effect.
Department of Ecological and Engineering, Toyohashi University of Technology, Toyohashi 441-8580, Japan; Department of Civil and Environmental Engineering, National Institute of Technology, Kure College, Kure 737-8506, Japan.
Zen-Ichiro
Z
Kimura
Department of Ecological and Engineering, Toyohashi University of Technology, Toyohashi 441-8580, Japan.
Yusuke
Y
Hirano
Department of Ecological and Engineering, Toyohashi University of Technology, Toyohashi 441-8580, Japan.
Yukiko
Y
Matsuzawa
Department of Ecological and Engineering, Toyohashi University of Technology, Toyohashi 441-8580, Japan; Department of Environmental and Life Sciences, Toyohashi University of Technology, Toyohashi 441-8580, Japan. Electronic address: hiraishi@ens.tut.ac.jp.
Akira
A
Hiraishi
D020561:Alphaproteobacteria / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D001420:Bacteria, Aerobic / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology*; D002733:Chlorophenols / Q000494:pharmacology*; D058645:Denaturing Gradient Gel Electrophoresis; D017404:In Situ Hybridization, Fluorescence; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012722:Sewage / Q000737:chemistry* / Q000382:microbiology*
D002733:Chlorophenols; D012336:RNA, Ribosomal, 16S; D012722:Sewage; C116190:3,5-dichlorophenol
3,5-Dichlorophenol; Bacterial community dynamics; Polyphasic approach; Sludge reduction; Uncoupler