Abstract
S. aureus USA300 isolates utilize the copBL and copAZ gene products to prevent Cu intoxication. We created and examined a ΔcopAZ ΔcopBL mutant strain (cop‐). The cop‐ strain was sensitive to Cu and accumulated intracellular Cu. We screened a transposon (Tn) mutant library in the cop‐ background and isolated strains with Tn insertions in the mntABC operon that permitted growth in the presence of Cu. The mutations were in mntA and they were recessive. Under the growth conditions utilized, MntABC functioned in manganese (Mn) import. When cultured with Cu, strains containing a mntA::Tn accumulated less Cu than the parent strain. Mn(II) supplementation improved growth when cop‐ was cultured with Cu and this phenotype was dependent upon the presence of MntR, which is a repressor of mntABC transcription. A ΔmntR strain had an increased Cu load and decreased growth in the presence of Cu, which was abrogated by the introduction of mntA::Tn. Over‐expression of mntABC increased cellular Cu load and sensitivity to Cu. The presence of a mntA::Tn mutation protected iron‐sulfur (FeS) enzymes from inactivation by Cu. The data presented are consistent with a model wherein defective MntABC results in decreased cellular Cu accumulation and protection to FeS enzymes from Cu poisoning.
To combat antibiotic resistance, we need to develop new prevention and therapeutic approaches. Copper (Cu) has shown promise as an antimicrobial compound; however, questions remain about how Cu enters cells, kills microorganisms, and how microorganisms prevent intoxication by Cu. Here, we present data showing that a dysfunctional MntABC Mn transporter results in decreased cellular Cu accumulation. We also demonstrate that cytosolic Cu accumulation inhibits S. aureus FeS enzymes.