Deciphering the function of Com_YlbF domain-containing proteins in .

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