Bacteria of the Candidate Phylum TM7 are Prevalent in Acidophilic Nitrifying Sequencing-Batch Reactors

摘要: Laboratory-scale acidophilic nitrifying sequencing-batch reactors (ANSBRs) were constructed by seeding with sewage-activated sludge and cultivating ammonium-containing acidic mineral medium (pH 4.0) or without a trace amount of yeast extract. In every batch cycle, the pH varied between 2.7 4.0, ammonium was completely converted to nitrate. Attempts detect functional genes in fully acclimated ANSBRs PCR previously designed primers mostly gave negative results. 16S rRNA gene-targeted subsequent denaturating gradient gel electrophoresis analysis revealed that marked change occurred bacterial community during overall period operation, which members candidate phylum TM7 class Gammaproteobacteria became predominant at stage. This result supported gene clone library analysis, as major phylogenetic groups clones detected (>5% total) (33%), (37%), Actinobacteria (10%), Alphaproteobacteria (8%). Fluorescence situ hybridization specific probes also demonstrated prevalence bacteria Gammaproteobacteria. These results suggest unknown microorganisms may play role ANSBRs; however, ecophysiological significance predominating this process remains unclear.