Cobalamin (vitamin B12) biosynthetic genes of Salmonella typhimurium

R. M. Jeter, J. R. Roth

Research output: Contribution to journalArticle

40 Scopus citations

Abstract

The enteric bacterium Salmonella typhimurium synthesizes cobalamin (vitamin B12) de novo only under anaerobic growth conditions. We initiated a genetic analysis of the cobalamin biosynthetic (cob) gene cluster. Stable cob::lac operon fusions were generated by insertions of a transposition-defective derivative of bacteriophage Mu d1 (Ap lac) into the cob genes. β-Galactosidase synthesis was repressed in the presence of exogenously supplied cyanocobalamin, demonstrating that the cobalamin biosynthetic pathway was regulated by end-product repression. Transcriptional polarity studies showed that the cob genes responsible for synthesis of the corrinoid intermediate cobinamide (branch I of the pathway) were organized into a single operon. Genes for the synthesis of 5,6-dimethylbenzimidazole (branch II) and the final assembly of the complete cobalamin molecule (branch III) were organized into two or more additional operons. All of the known cob genes (in branches I, II, and III) were transcribed in a counterclockwise direction relative to the S. typhimurium genetic map. These genes are located at 41 map units and near the his operon. No essential genes lie between the his and cob operons. Mutants that carried deletions extending from the his genes into the cob region were isolated and characterized. By using these mutants, a deletion map of the branch I cob operon was constructed and the order of genes (his-cobI-cobIII-cobII) was inferred.

Original languageEnglish (US)
Pages (from-to)3189-3198
Number of pages10
JournalJournal of Bacteriology
Volume169
Issue number7
StatePublished - 1987
Externally publishedYes

ASJC Scopus subject areas

  • Applied Microbiology and Biotechnology
  • Immunology

Fingerprint Dive into the research topics of 'Cobalamin (vitamin B<sub>12</sub>) biosynthetic genes of Salmonella typhimurium'. Together they form a unique fingerprint.

  • Cite this