Investigating the roles of Na+/H+ antiporters nhaC and SAUSA300_0617 during Staphylococcus aureus nitrosative stress

Albert Chow

Biology

Melinda Grosser

Methicillin-resistant Staphylococcus aureus (MRSA), a Gram-positive bacterium, is one of the most virulent clinical pathogens due to its numerous defense mechanisms against the host innate immune response. Antibiotic-resistant strains have emphasized the need to identify new drug targets. Recent research has examined the role of nitric oxide (NO•), an immune effector. While the presence of NO• inhibits microbial growth, S. aureus has unique adaptations to resist nitrosative stress. A pooled transposon screen studying a strain of MRSA (USA300 LAC) identified 168 genes that were likely essential for NO• resistance. Two were genes encoding Na+/H+ antiporters, including nhaC and SAUSA300_0617. An earlier study identified the significance of NhaC during pH and salt stress. This research evaluated the roles of these two antiporter genes during nitrosative stress through creation of two deletion mutants, △nhaC and △0617. While the transposon screen identified both to be essential for NO• resistance, we found that exposure to NO• slowed but did not stop growth in the △0617 deletion mutant compared to wild-type. Growth inhibition of the mutant became more pronounced at higher concentrations. This confirms that SAUSA300_0617 aids in S. aureus NO• resistance but is not essential for growth and survival during nitrosative stress. Investigation of the ∆nhaC mutant is still in progress. Future studies will identify the phenotype of additional single deletion mutants of S. aureus that encode Na+/H+ antiporters and determine their suitability as potential drug targets.

Jan-9-2024