Biosynthesis of poly-beta-hydroxybutyrate (PHB) is controlled by CydR (Fnr) in the obligate aerobe Azotobacter vinelandii

FEMS Microbiol Lett. 2001 Jan 15;194(2):215-20. doi: 10.1111/j.1574-6968.2001.tb09472.x.


CydR is an Fnr-like protein in the obligatory aerobic nitrogen-fixing bacterium Azotobacter vinelandii. The cydR mutant overproduces the cytochrome bd terminal oxidase. Using two-dimensional polyacrylamide gel electrophoresis, we showed that beta-ketothiolase and acetoacetyl-CoA reductase were also overexpressed in the cydR mutant. Fumarase C and a coenzyme A transferase, possibly succinyl-SCoA transferase, were decreased in this mutant. Enzyme assays confirmed the elevated beta-ketothiolase and acetoacetyl-CoA reductase activities in this mutant. The cydR mutant accumulated poly-beta-hydroxybutyrate throughout the exponential growth phase, unlike the wild-type strain that only accumulated poly-beta-hydroxybutyrate during stationary phase. The results demonstrate that CydR controls poly-beta-hydroxybutyrate synthesis in A. vinelandii.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Azotobacter vinelandii / metabolism*
  • Bacterial Proteins / metabolism*
  • Electrophoresis, Polyacrylamide Gel
  • Hydroxybutyrates / metabolism*
  • Polyesters / metabolism*
  • Repressor Proteins / metabolism*


  • Bacterial Proteins
  • CydR protein, Azotobacter vinelandii
  • Hydroxybutyrates
  • Polyesters
  • Repressor Proteins
  • poly-beta-hydroxybutyrate