Deciphering the function of Com_YlbF domain-containing proteins in <i>Staphylococcus aureus</i>

The Com_YlbF domain-containing proteins inhibit sporulation, competition, and biofilm formation by affecting the activity of ribonuclease RNase-Y in <i>Bacillus subtilis</i>. Similar Com_YlbF proteins are found in <i>Staphylococcus aureus</i>, 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 <i>S. aureus</i> by evaluating the impact of <i>qrp/yheA</i>, <i>ymcA</i>, and <i>ylbF</i> gene deletion on biofilm formation, PIA/PNAG production, and hemolytic capacity. It was found that deletion of the three <i>qrp/yheA</i>, <i>ymcA</i>, and <i>ylbF</i> genes in <i>S. aureus</i> 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 <i>agrA</i> gene (quorum sensing system), the <i>delta</i>, <i>alpha</i>, and <i>gamma</i> hemolysins, as well as the <i>sdrC</i> genes and <i>eap/map</i> (adhesion proteins) genes. It also showed an attenuation of virulence, manifesting as enhanced survival among <i>Galleria mellonella</i> larvae and BALB/c mice, possibly associated due to disrupted RNase-Y activity when the <i>qrp/yheA</i>, <i>ymcA</i>, and <i>ylbF</i> 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 <i>S. aureus</i> 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 <i>Bacillus subtilis</i> (reduction of biofilm ability, sporulation, and competence). However, the role of these proteins in <i>S. aureus</i> has been little studied. This study shows the importance of the Com_YlbF protein family in <i>S. aureus</i> 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 <i>S. aureus</i>.