Phosphatase production and activity in Citrobacter freundii and a naturally occurring, heavy-metal-accumulating Citrobacter sp

Microbiology. 1995 Oct;141 ( Pt 10):2433-41. doi: 10.1099/13500872-141-10-2433.

Abstract

The ability of a naturally occurring Citrobacter sp. to accumulate cadmium has been attributed to cellular precipitation of CdHPO4, utilizing HPO4(2-) liberated via the activity of an overproduced, Cd-resistant acid-type phosphatase. Phosphatase production and heavy metal accumulation by batch cultures of this strain (N14) and a phosphatase-deficient mutant were compared with two reference strains of Citrobacter freundii. Only strain N14 expressed a high level of acid phosphatase and accumulated lanthanum and uranyl ion enzymically. Acid phosphatase is regulated via carbon-starvation; although the C. freundii strains overexpressed phosphatase activity in carbon-limiting continuous culture, this was approximately 20-fold less than the activity of strain N14 grown similarly. Citrobacter strain N14 was originally isolated from a metal-contaminated soil environment; phosphatase overproduction and metal accumulation were postulated as a detoxification mechanism. However, application of Cd-stress, and enrichment for Cd-resistant C. freundii ('training'), reduced the phosphatase activity of this organism by about 50% as compared to Cd-unstressed cultures. The acid phosphatase of C. freundii and Citrobacter N14 had a similar pattern of resistance to some diagnostic reagents. The enzyme of the latter is similar to the PhoN acid phosphatase of Salmonella typhimurium described by other workers; the results are discussed with respect to the known phosphatases of the enterobacteria.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acid Phosphatase / biosynthesis*
  • Acid Phosphatase / drug effects
  • Cadmium / metabolism
  • Cadmium / pharmacology
  • Citrobacter freundii / enzymology*
  • Citrobacter freundii / metabolism
  • Drug Resistance, Microbial
  • Gene Expression Regulation, Enzymologic*
  • Inactivation, Metabolic
  • Lanthanum / metabolism
  • Metals / metabolism*
  • Species Specificity
  • Uranium Compounds / metabolism

Substances

  • Metals
  • Uranium Compounds
  • Cadmium
  • Lanthanum
  • Acid Phosphatase