Staphylococcus aureus is an important raw milk contaminant that can persist in dairy environments through biofilm formation and adaptation to environmental stresses. Although the alternative sigma factor SigH has been described in S. aureus, its role in raw milk-associated strains remains poorly understood. In this study, we investigated the function of SigH in the raw milk-derived S. aureus strain RMSA24 in biofilm formation, stress tolerance and antibiotic susceptibility. Deletion of sigH did not affect bacterial growth under routine culture conditions but significantly reduced biofilm formation. In contrast, the sigH mutant exhibited enhanced tolerance to osmotic, acid, and heat stresses. Loss of sigH also reduced susceptibility to the glycopeptide antibiotics vancomycin and teicoplanin and was accompanied by pronounced cell wall thickening. Transcriptomic analysis further supported these phenotypes by revealing differential expression of genes associated with biofilm formation, stress tolerance, and cell wall homeostasis. Overall, these findings indicate that SigH contributes to the regulation of persistence-associated phenotypes in a raw milk-derived S. aureus strain and provide new insights into the regulatory mechanisms that may influence survival of this pathogen in dairy-related environments.
Chao Li, Fanwenqing Kong, Wenting Li et al.· Journal of Dairy Science· 0 citations
Staphylococcus aureus has significantly contributed to the contamination of dairy products and preserved foods, attributed to its ability to colonize a wide range of environments and form biofilms. ArcR, the Crp/Fnr family regulatory protein in S. aureus plays key roles in various biological processes. However, the molecular mechanism underlying biofilm regulation by the cAMP-ArcRsa complex remains poorly defined. In this work, we investigated the biological function of ArcRsa in mediating biofilm formation in dairy-derived S. aureus RMSA49. The results demonstrated that the deletion of arcRsa resulted in a dramatic increase in biofilm formation. An in-depth dissection of the regulatory mechanism of ArcRsa revealed that it negatively regulates the production of the polysaccharide intercellular adhesin (PIA) by directly binding to the promoter of the gene icaA. Further analysis revealed that cAMP-ArcRsa complex support biofilm maintenance of S. aureus RMSA 49 by strengthening its regulation of genes icaA. ArcRsa controls the transcription of its own gene and icaA by attaching to specific sequences at the site arcRsa (5'-ATCACGCGACAA-3') and site arcRsa2 (5'-ATTAAGTTGCAA-3'). Our results demonstrate functional crosstalk between cAMP and ArcRsa through direct regulation at the gene icaA promoter, supporting an essential regulatory role for the cAMP-ArcRsa signaling module in modulating biofilm formation in S. aureus.
Haoyang He, Fanwenqing Kong, Xiaojia Xuan et al.· Journal of Dairy Science· 0 citations
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