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

Abstract

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

Rhizosphere microbiome selection by Epichloë endophytes of Festuca arundinacea

“…While candidate Division TM7 DNA has been reported from soil, freshwater, hot springs and termite guts, this group of bacteria has been referred to as biology's Bdark matter^due to the lack of axenic cultures for physiological examination (Dinis et al 2011). However, sequencing has shown that these strains harbor genes for nitrification and chitinase, which could be beneficial to E+ plants (Hanada et al 2014).…”

Distribution of Phototrophic Purple Nonsulfur Bacteria in Massive Blooms in Coastal and Wastewater Ditch Environments

“…Purified isolates were preserved in RPL2 agar medium as stub cultures. The 16S rRNA genes from the cell lysate [36] were PCR-amplified with bacterial universal primers 27f and 1492r (see Table S1) [37] and sequenced by the Sanger method using a cycle sequencing kit and an automated DNA sequencer [38]. Sequence data were compiled using the GENETYX-MAC program (GENETYX, Tokyo, Japan) and subjected to EzBioCloud [39] and BLAST [40] homology searches for phylogenetic identification.…”

Effect of Carbon to Nitrogen Ratio on Water Quality and Community Structure Evolution in Suspended Growth Bioreactors through Biofloc Technology

“…Saccharibacteria (former candidate division TM7, also called candidate phylum Saccharibacteria) is frequently found in various natural environments and activated sludge which makes it a beneficial candidate phylum [29]. However, Hanada [45] also reported the prevalence of candidate division TM7 in an acidophilic nitrified SBR (sequencing batch reactor) which was added to simulative wastewater made up of ammonium and other salts without a carbon source. Interestingly, Zhao [46] reported that the most suitable salinity for candidate division TM7 is 2%, which is very close to the salinity in the SGBRs.…”