ABSTRACT: The Com_YlbF domain-containing proteins inhibit sporulation, competition, and biofilm formation by affecting the activity of ribonuclease RNase-Y in Bacillus subtilis. Similar Com_YlbF proteins are found in Staphylococcus aureus, but their function is yet to be determined. This study investigates the role of Com_YlbF domain-containing proteins (Qrp/YheA, YmcA, and YlbF) in S. aureus by evaluating the impact of qrp/yheA, ymcA, and ylbF gene deletion on biofilm formation, PIA/PNAG production, and hemolytic capacity. It was found that deletion of the three qrp/yheA, ymcA, and ylbF genes in S. aureus produced a decrease in biofilm formation, a slight decrease in PIA/PNAG production, and a decrease in its hemolytic capacity. Global transcriptional analysis in the mutant strain showed dysregulation of several genes associated with pathogenesis, most notably a decreased expression of the agrA gene (quorum sensing system), the delta, alpha, and gamma hemolysins, as well as the sdrC genes and eap/map (adhesion proteins) genes. It also showed an attenuation of virulence, manifesting as enhanced survival among Galleria mellonella larvae and BALB/c mice, possibly associated due to disrupted RNase-Y activity when the qrp/yheA, ymcA, and ylbF are deleted. In conclusion, this work supports the hypothesis that this new family of proteins containing a Com_YlbF domain is involved in the regulation of genes related to biofilm formation, hemolysis, and virulence in S. aureus through a change in RNase-Y activity.IMPORTANCEThe Com_YlbF proteins are a group of small proteins identified in some Gram-positive bacteria whose function has not been described, but whose deletion has been related to pleiotropic effects in Bacillus subtilis (reduction of biofilm ability, sporulation, and competence). However, the role of these proteins in S. aureus has been little studied. This study shows the importance of the Com_YlbF protein family in S. aureus involved in biofilm formation and hemolysis. The phenotypes could be explained by an alteration of the enzymatic activity of the endoribonuclease RNase-Y, resulting in reduced secretion of virulence factors. These findings represent a significant step forward in understanding the modulation of pathogenesis and virulence in S. aureus.
