Regulation of nitrogen metabolism in the nitrate-ammonifying soil bacterium Bacillus vireti and evidence for its ability to grow using N2 O as electron acceptor

Environ Microbiol. 2016 Sep;18(9):2937-50. doi: 10.1111/1462-2920.13124. Epub 2016 Jan 18.

Abstract

Bacillus vireti is a nitrate-ammonifying bacterium and a partial denitrifier, reducing NO3 (-) , NO2 (-) , NO and N2 O with NarG, NrfA, CbaA and NosZ respectively. Growth is optimized through successive use of the electron acceptors O2 and NO3 (-) , followed by NO2 (-) , NO and N2 O. Fermentation takes place simultaneously with anaerobic respiration. When grown in batch culture with 5 mM initial NO3 (-) , transcription of nrfA was high and most NO3 (-) was reduced to NH4 (+) . With 20 mM initial NO3 (-) , nrfA transcription was lower and more than 50% of the nitrate was recovered as NO, N2 O and N2 . Analysis of gene transcription patterns and corresponding gas kinetics indicated that O2 and NO2 (-) or NO are main controllers of nrfA, nirB, cbaA and nosZ transcription. This was corroborated by analyses of putative binding regions for specific transcriptional regulators. Furthermore, we demonstrate that N2 O reduction in B. vireti supports growth. The high nosZ transcription but low N2 O production seen at 5 mM NO3 (-) implies that this organism can use N2 O reductase to scavenge N2 O from other organisms in the soil, thus possibly acting as a net sink for N2 O.

MeSH terms

  • Ammonia / metabolism*
  • Bacillus / classification
  • Bacillus / genetics
  • Bacillus / isolation & purification
  • Bacillus / metabolism*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Electrons
  • Nitrates / metabolism*
  • Nitrous Oxide / metabolism*
  • Oxidoreductases / genetics
  • Oxidoreductases / metabolism
  • Soil Microbiology*

Substances

  • Bacterial Proteins
  • Nitrates
  • Ammonia
  • Oxidoreductases
  • Nitrous Oxide