Interspecies interactions in dual-species biofilms formed by Staphylococcus aureus and Candida albicans: Phenotypic and transcriptomic insights.

In the dairy processing and clinical medical environments, Candida albicans and Staphylococcus aureus can coexist on the surfaces of equipment or medical devices, forming difficult-to-eradicate dual-species biofilms that exacerbate dairy spoilage and clinical co-infections. However, the interaction mechanism between these two microorganisms are still unclear. This study employed a combined approach of phenotypic analysis (crystal violet staining, colony counting, XTT reduction assay, extracellular polymer (EPS) quantification, and optical microscopy) coupled with dual transcriptomics and RT-qPCR validation to systematically analyze the interaction mechanism of the co-culture of the two species. The results revealed that there is an antagonistic effect between C. albicans and S. aureus. This is mainly manifested as: compared with the single-species biofilm, the dual-species biofilm exhibited significantly reduced biomass, cell counts, metabolic activity, and EPS content, along with a notably looser biofilm structure. RNA-seq analysis further demonstrated that in S. aureus, pathways related to quorum sensing, carbohydrate and amino acid metabolism were suppressed, whereas in C. albicans, the MAPK signaling pathway, autophagy regulation, and energy metabolism were significantly downregulated. This study provides a molecular theoretical basis for the development of anti-biofilm agents in food co-colonization environments and for the intervention of clinical co-infections.