High-level resistance to cobalt and nickel but probably no transenvelope efflux: Metal resistance in the Cuban Serratia marcescens strain C-1.
Molecular mechanisms underlying inducible cobalt and nickel resistance of a bacterial strain isolated from a Cuban serpentine deposit were investigated. This strain C-1 was assigned to Serratia marcescens by 16S rDNA analysis and DNA/DNA hybridization. Genes involved in metal resistance were identified by transposon mutagenesis followed by selection for cobalt- and nickel-sensitive derivatives. The transposon insertion causing the highest decrease in metal resistance was located in the ncrABC determinant. The predicted NcrA product was a NreB ortholog of the major facilitator protein superfamily and central for cobalt/nickel resistance in S. marcescens strain C-1. NcrA also mediated metal resistance in Escherichia coli and caused decreased accumulation of Co(II) and Ni(II) in this heterologous host. NcrB may be a regulatory protein. NcrC was a protein of the nickel-cobalt transport (NiCoT) protein family and necessary for full metal resistance in E. coli, but only when NcrA was also present. Without NcrA, NcrC caused a slight decrease in metal resistance and mediated increased accumulation of Ni(II) and Co(II). Because the cytoplasmic metal concentration can be assumed to be the result of a flow equilibrium of uptake and efflux processes, this interplay between metal uptake system NcrC and metal efflux system NcrA may contribute to nickel and cobalt resistance in this bacterium.
Marrero
Jeannette
J
Institut für Mikrobiologie, Martin-Luther-Universität Halle-Wittenberg, Halle/Saale, Germany.
Auling
Georg
G
Coto
Orquidea
O
Nies
Dietrich H
DH
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D003035:Cobalt / Q000378:metabolism / Q000494:pharmacology*; D003462:Cuba; D004251:DNA Transposable Elements; D024881:Drug Resistance, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009532:Nickel / Q000378:metabolism / Q000494:pharmacology*; D017422:Sequence Analysis, DNA; D012706:Serratia marcescens / Q000187:drug effects* / Q000235:genetics* / Q000378:metabolism
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D003035:Cobalt; D009532:Nickel