Investigation on the anaerobic propionate degradation by Escherichia coli K12

Mol Microbiol. 2017 Jan;103(1):55-66. doi: 10.1111/mmi.13541. Epub 2016 Oct 20.


Propionate is an abundant carboxylic acid in nature. Microorganisms metabolize propionate aerobically via the 2-methylcitrate pathway. This pathway depends on a series of three reactions in the citric acid cycle that leads to the conversion of succinate to oxaloacetate. Interestingly, the γ-proteobacterium Escherichia coli can use propionate as a carbon and electron source under oxic but not under anoxic conditions. RT-PCR and transcriptomic analysis revealed a posttranscriptional regulation of the prpBCDE-gene cluster encoding the necessary enzymes for propionate metabolism. The polycistronic mRNA seems to be hydrolyzed in the 3'-5' direction under anoxic conditions. This regulatory strategy is highly constructive because the last gene of the operon encodes the first enzyme of the propionate metabolism. Further analysis revealed that RNase R is involved in the hydrolysis of the prp transcripts. Consequently, an rnr-deletion strain could metabolize propionate under anoxic conditions. To the best of our knowledge, this is the first study describing the influence of RNase R on the anaerobic metabolism of E. coli.

MeSH terms

  • Anaerobiosis / physiology
  • Citrates / metabolism
  • Citric Acid Cycle / physiology
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Escherichia coli K12 / genetics
  • Escherichia coli K12 / metabolism*
  • Escherichia coli Proteins / metabolism*
  • Exoribonucleases / metabolism*
  • Gene Expression Regulation, Bacterial / genetics
  • Multigene Family / genetics
  • Operon / genetics
  • Propionates / metabolism*


  • Citrates
  • Escherichia coli Proteins
  • Propionates
  • rnr protein, E coli
  • 2-methylcitric acid
  • Exoribonucleases