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

Citation
Zq. Hao et al., Characterization of cadmium uptake in Lactobacillus plantarum and isolation of cadmium and manganese uptake mutants, APPL ENVIR, 65(11), 1999, pp. 4741-4745
Citations number
23
Categorie Soggetti
Biology,Microbiology
Journal title
APPLIED AND ENVIRONMENTAL MICROBIOLOGY
ISSN journal
00992240 → ACNP
Volume
65
Issue
11
Year of publication
1999
Pages
4741 - 4745
Database
ISI
SICI code
0099-2240(199911)65:11<4741:COCUIL>2.0.ZU;2-K
Abstract
Two different Cd2+ uptake systems were identified in Lactobacillus plantaru m. One is a high-affinity, high-velocity Mn2+ uptake system which also take s up Cd2+ and is induced by Mn2+ starvation. The calculated K-m and V-max a re 0.26 mu M and 3.6 mu mol g of dry cell(-1) min(-1), respectively. Unlike Mn2+ uptake, which is facilitated by citrate and related tricarboxylic aci ds, Cd2+ uptake is weakly inhibited by citrate. Cd2+ and Mn2+ are competiti ve inhibitors of each other, and the affinity of the system for Cd2+ is hig her than that for Mn2+. The other Cd2+ uptake system is expressed in Mn2+-s ufficient cells, and no K-m can be calculated for it because uptake is nons aturable. Mn2+ does not compete for transport through this system, nor does any other tested cation, i.e,, Zn2+, Cu2+, Co2+, Mg2+, Ca2+, Fe2+, or Ni2, Both systems require energy, since uncouplers completely inhibit their ac tivities. Two Mn2+-dependent L, plantarum mutants were isolated by chemical mutagenesis aod ampicillin Enrichment. They required more than 5,000 times as much Mn2+ for growth as the parental strain. Mn2+ starvation-induced Cd 2+ uptake in both mutants was less than 5% the wild-type rate. The low leve l of long-term Mn2+ or Cd2+ accumulation by the mutant strains also shows t hat the mutations eliminate the high-affinity Mn2+ and Cd2+ uptake system.