cobB function is required for catabolism of propionate in Salmonella typhimurium LT2: evidence for existence of a substitute function for CobB within the 1,2-propanediol utilization (pdu) operon

J Bacteriol. 1996 Dec;178(23):7016-9. doi: 10.1128/jb.178.23.7016-7019.1996.


The cobB function of Salmonella typhimurium LT2 was defined in vivo as an alternative activity for the nicotinic acid mononucleotide:5,6-dimethylbenzimidazole phosphoribosyltransferase enzyme (CobT), which is involved in the assembly of the nucleotide loop of cobalamin in this bacterium (J. R. Trzebiatowski, G. A. O'Toole, and J. C. Escalante-Semerena, J. Bacteriol. 176:3568-3575, 1994). In this paper we document that, independent of their inability to substitute for CobT function, cobB mutants are unable to use propionate as a carbon and energy source. A plasmid carrying only a wild-type copy of cobB complemented the cobalamin biosynthesis and propionate catabolism phenotypes of cobB mutants, indicating that a lack of CobB was responsible for both phenotypes. We demonstrate the existence of a function encoded by the 1,2-propanediol utilization (pdu) operon, which when induced by 1,2-propanediol compensated for the lack of CobB during propionate catabolism but failed to compensate for CobT in the assembly of the nucleotide loop of cobalamin in a cobB cobT double mutant.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Genes, Bacterial*
  • Mutation
  • Operon*
  • Propionates / metabolism*
  • Propylene Glycol
  • Propylene Glycols / metabolism*
  • Salmonella typhimurium / genetics*
  • Salmonella typhimurium / metabolism
  • Vitamin B 12 / biosynthesis


  • Propionates
  • Propylene Glycols
  • Propylene Glycol
  • Vitamin B 12