Reduced cadmium transport determined by a resistance plasmid in Staphylococcus aureus.
The presence of a plasmid harboring a gene for Cd2+ resistance led to markedly reduced Cd2+ uptake via the energy-dependent Mn2+ transport system in Staphylococcus aureus strain 17810R. Cd2+ uptake by the resistant strain via this high-affinity system was seen only at very low Cd2+ concentrations. At high concentrations, Cd2+ was taken up by the resistant strain via a different low-affinity uptake system. Cd2+ uptake via this system was energy dependent but was not blocked by Mn2+. Loss of the plasmid from the resistant strain resulted in Cd2+ sensitivity and unblocking of Cd2+ transport via the Mn2+ carrier in the plasmidless derivative strain 17810S. The energy-dependent Cd2+ uptake by the sensitive strain was inhibited by Mn2+ with kinetics indicating competitive inhibition. It is suggested that the second, low-affinity uptake system for Cd2+ in the resistant strain is the energy-dependent cadmium/proton antiporter, which at low Cd2+ concentrations functions in net Cd2+ efflux.
D001693:Biological Transport, Active; D002104:Cadmium / Q000378:metabolism* / Q000494:pharmacology; D007700:Kinetics; D008345:Manganese / Q000378:metabolism; D011815:R Factors; D013211:Staphylococcus aureus / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D013696:Temperature
D002104:Cadmium; D008345:Manganese