The role of nitric oxide synthase in biofilm formation by Staphylococcus aureus

Staphylococcus aureus is capable of colonizing diverse environments and forming biofilms. In this study, we found that the knockout of NO synthase (NOS) impaired biofilm integrity, resulting in weakened biofilms. We found the deletion of the nos reduced intracellular NO levels, which subsequently altered the S-nitrosylation modification levels of the proteome. This alteration was particularly pronounced in the S-nitrosylation modification of the cysteine residue at position 12 of the MgrA. This modification reduced the binding affinity of MgrA to the promoter of the acetyltransferase gene (icaA), resulting in reduced levels of poly-N-acetyl-β-(1-6)-glucosamine (PIA), a key component of biofilms formed by S. aureus, thereby further weakening biofilm formation. Consequently, we conclude that NOS in S. aureus S-nitrosylates the MgrA through the synthesis of endogenous NO. This process strengthens the interaction between MgrA and the icaA promoter (P_icaA), thereby enhancing the synthesis of major polysaccharides in biofilms and promoting biofilm formation.