Single-cell approach dissecting agr quorum sensing dynamics in Staphylococcus aureus
RNAseq of exponentially growing cultures of the four agr prototype strains used in the study to investigate if differential expression of regulators interacting with the agr system could explain the differences in AIP sensitivity.  Abstract Staphylococcus aureus both colonizes humans and causes severe virulent infections. Virulence is regulated by the agr quorum sensing system and its autoinducing peptide (AIP), with dynamics at the single-cell level across four agr-types – each defined by distinct AIP sequences and capable of cross-inhibition – remaining elusive. Employing microfluidics, time-lapse microscopy, and deep-learning image analysis, we uncovered significant differences in AIP sensitivity among agr-types. We observed bimodal agr activation, attributed to intergenerational phenotypic stability and influenced by AIP concentration. Upon AIP stimulation, agr III showed AIP insensitivity, while agr II exhibited increased sensitivity and prolonged generation time. Beyond expected cross-inhibition of agr I by heterologous AIP II and  III, the presumably cross-activating AIP IV also inhibited agr I. Community interactions across different agr-type pairings revealed four main patterns: stable or switched dominance, and delayed or stable dual activation, influenced by community characteristics. These insights underscore the potential of personalized treatment strategies considering virulence and genetic diversity.