Characterization of cadmium uptake in Lactobacillus plantarum and isolation of cadmium and manganese uptake mutants

Journal Article · Mon Nov 01 04:00:00 EST 1999 · Applied and Environmental Microbiology

OSTI ID:20005469

Hao, Z; Reiske, H R; Wilson, D B

Two different Cd{sup 2+} uptake systems were identified in Lactobacillus plantarum. One is a high-affinity, high-velocity Mn{sup 2+} uptake system which also takes up Cd{sup 2+} and is induced by Mn{sup 2+} starvation. The calculated K{sub m} and V{sub max} are 0.26 {mu}M and 3.6 {mu}mol g of dry cell{sup {minus}1} min{sup {minus}1}, respectively. Unlike Mn{sup 2+} uptake, which is facilitated by citrate and related tricarboxylic acids, Cd{sup 2+} uptake is weakly inhibited by citrate. Cd{sup 2+} and Mn{sup 2+} are competitive inhibitors of each other, and the affinity of the system for Cd{sup 2+} is higher than that for Mn{sup 2+}. The other Cd{sup 2+} uptake system is expressed in Mn{sup 2+}-sufficient cells, and no K{sub m} can be calculated for it because uptake is nonsaturable. Mn{sup 2+} does not compete for transport through this system, nor does any other tested cation, i.e., Zn{sup 2+}, Cu{sup 2+}, Co{sup 2+}, Mg{sup 2+}, Ca{sup 2+}, Fe{sup 2+}, or Ni{sup 2+}. Both systems require energy, since uncouplers completely inhibit their activities. Two Mn{sup 2+}-dependent L. plantarum mutants were isolated by chemical mutagenesis and ampicillin enrichment. They required more than 5,000 times as much Mn{sup 2+} for growth as the parental strain. Mn{sup 2+} starvation-induced Cd{sup 2+} uptake in both mutants was less than 5% the wild-type rate. The low level of long-term Mn{sup 2+} or Cd{sup 2+} accumulation by the mutant strains also shows that the mutations eliminate the high-affinity Mn{sup 2+} and Cd{sup 2+} uptake system.

• Research Organization: Cornell Univ., Ithaca, NY (US)
• OSTI ID: 20005469
• Journal Information: Applied and Environmental Microbiology, Journal Name: Applied and Environmental Microbiology Journal Issue: 11 Vol. 65; ISSN AEMIDF; ISSN 0099-2240
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
BIODEGRADATION
CADMIUM
CALCIUM
COBALT
COPPER
IRON
LACTOBACILLUS
MAGNESIUM
MANGANESE
MUTANTS
NICKEL
REMEDIAL ACTION
ZINC