title: Mechanisms of biodegradation of metal-citrate complexes by Pseudomonas fluorescens.
abstract: Biodegradation of metal-citrate complexes by Pseudomonas fluorescens depends on the nature of the complex formed between the metal and citric acid. Bidentate Fe(III)-, Ni-, and Zn-citrate complexes were readily biodegraded, but the tridentate Cd- and Cu-citrate, and U-citrate complexes were not. The biodegradation of Ni- and Zn-citrate commenced after an initial lag period; the former showed only partial (70%) degradation, whereas the latter was completely degraded. Uptake studies with 14C-labeled citric acid and metal-citrate complexes showed that cells grown in medium containing citric acid transported free citric acid at the rate of 28 nmol min-1 and Fe(III)-citrate at the rate of 12.6 nmol min-1 but not Cd-, Cu-, Ni-, U-, and Zn-citrate complexes. However, cells grown in medium containing Ni- or Zn-citrate transported both Ni- and Zn-citrate, suggesting the involvement of a common, inducible transport factor. Cell extracts degraded Fe(III)-, Ni-, U-, and Zn-citrate complexes in the following order: The cell extract did not degrade Cd- or Cu-citrate complexes. These results show that the biodegradation of the U-citrate complex was limited by the lack of transport inside the cell and that the tridentate Cd- and Cu-citrate complexes were neither transported inside the cell nor metabolized by the bacterium.
authors.affiliation: Department of Applied Science, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: G
authors.initials: G
authors.lastname: Joshi-Tope
authors.forename: A J
authors.initials: AJ
authors.lastname: Francis
mesh_terms: D000222:Adaptation, Physiological; D001673:Biodegradation, Environmental; D001693:Biological Transport, Active; D002104:Cadmium / Q000378:metabolism; D002951:Citrates / Q000378:metabolism* / Q000493:pharmacokinetics; D019343:Citric Acid; D005290:Ferric Compounds / Q000378:metabolism; D008670:Metals / Q000378:metabolism* / Q000493:pharmacokinetics; D009532:Nickel / Q000378:metabolism; D011551:Pseudomonas fluorescens / Q000254:growth & development / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D014501:Uranium / Q000378:metabolism
chemical_list: D002951:Citrates; D005290:Ferric Compounds; D008670:Metals; D002104:Cadmium; D019343:Citric Acid; D014501:Uranium; C025314:ferric citrate; D009532:Nickel