Exploring the copper resistance mechanism of the lipoprotein DcrB in Salmonella enterica

Abstract

Salmonella enterica is a major bacterial cause of foodborne illness and invasive disease. Salmonella establishes infections by evading host macrophages; these host immune cells engulf the bacteria into a phagosome and use mechanisms to destroy the foreign body. Within the phagosome, bacteria are subjected to many harsh conditions, one possibly being toxic amounts of copper metal ions. We have previously demonstrated that the periplasmic‐anchored lipoprotein DcrB (possessed by S. enterica serovar Typhimurium) conveys resistance to toxic concentrations of copper ions, and thereby may play a role in Salmonella’s survival within the host. To gain a better understanding of the protein’s function, we have explored gene expression affected by DcrB and possible interactions between the protein and small, cellular metabolites. Using reverse‐transcriptase quantitative PCR, we have shown that DcrB plays a role in the upregulation of some cell envelope stress response genes. DcrB, however, does not significantly affect regulation of copper ion transport genes or other copper ion resistance genes. Through thermofluor assays, we have shown that purified DcrB protein has increased stability in toxic copper ion concentrations when extracellular amino acids are present in solution. This result suggests that DcrB has copper‐dependent interactions with free amino acids. Overall, these findings advance our understanding of how DcrB confers resistance to copper ions. This knowledge could be used to develop new antibiotics targeting bacterial copper resistance, ultimately decreasing the number of invasive illnesses caused by S. enterica and other gram‐negative bacteria.Support or Funding InformationThis research was supported by a UWL Faculty Research Grant to JFM.