Degradation of 2-methylbenzoic acid by Pseudomonas cepacia MB2

Appl Environ Microbiol. 1992 Jan;58(1):194-200. doi: 10.1128/aem.58.1.194-200.1992.

Abstract

We report the isolation of Pseudomonas cepacia MB2, believed to be the first microorganism to utilize 2-methylbenzoic acid as the sole carbon source. Its growth range included all mono- and dimethylbenzoates (with the exception of 2,5- and 2,6-dimethylbenzoates) and 3-chloro-2-methylbenzoate (but not 4- or 5-chloro-2-methylbenzoate) but not chlorobenzoates lacking a methyl group. 2-Chlorobenzoate, 3-chlorobenzoate, and 2,3-, 2,4-, and 3,4-dichlorobenzoates inhibited growth of MB2 on 2-methylbenzoate as a result of cometabolism to the corresponding chlorinated catechols which blocked the key enzyme catechol 2,3-dioxygenase. A metapyrocatechase-negative mutant, MB2-G5, showed accumulation of dimethylcatechols from 2,3- and 3,4-dimethylbenzoates, and phenols were detected in resting-cell transformation extracts bearing the same substitution pattern as the original substrate, presumably following thermal degradation of the intermediate dihydrodiol. 2-Methylphenol was also found in extracts of the mutant cells with 2-methylbenzoate. These observations suggested a major route of methylbenzoate metabolism to be dioxygenation to a carboxy-hydrodiol which then forms a catechol derivative. In addition, the methyl group of 2-methylbenzoate was oxidized to isobenzofuranone (by cells of MB2-G5) and to phthalate (by cells of a separate mutant that could not utilize phthalate, MB2-D2). This pathway also generated a chlorinated isobenzofuranone from 3-chloro-2-methylbenzoate.

Publication types

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

MeSH terms

  • Benzoates / chemistry
  • Benzoates / metabolism*
  • Biodegradation, Environmental
  • Burkholderia cepacia / growth & development
  • Burkholderia cepacia / metabolism*
  • Catechol 1,2-Dioxygenase
  • Catechol 2,3-Dioxygenase
  • Chlorobenzoates / pharmacology
  • Dioxygenases*
  • Mass Spectrometry
  • Molecular Structure
  • Oxygenases / metabolism

Substances

  • Benzoates
  • Chlorobenzoates
  • methyl benzoate
  • Oxygenases
  • Dioxygenases
  • Catechol 1,2-Dioxygenase
  • Catechol 2,3-Dioxygenase