An acyl-homoserine lactone acylase found in Stenotrophomonas maltophilia exhibits both quorum quenching activity and the ability to degrade penicillin antibiotics

Abstract

Stenotrophomonas maltophilia are opportunistic, multi-drug-resistant Gram-negative pathogens increasingly prevalent in clinical settings. Quorum sensing (QS) systems play a crucial role in their pathogenesis, coordinating bacterial populations and enabling interactions within polymicrobial communities. While not the primary QS mechanism in S. maltophilia, these bacteria can respond to acyl-homoserine lactone (AHL)-type autoinducers. Some isolates exhibit AHL-quorum quenching activity, though the responsible components remain unidentified. Homology searches in S. maltophilia K279a revealed a protein with the locus tag SMLT_RS07305 (old locus tag Smlt1522), annotated as a putative penicillin acylase 2 precursor. Sequence and structural analyses classify this protein within the bacterial AHL-acylase group B, characterized by a heterodimeric structure consisting of α- and β-subunits connected by a spacer polypeptide. We experimentally confirmed the dual activity of Smlt1522 as an AHL-acylase and a penicillin acylase. This protein degrades AHLs with varying acyl chains and hydrolyses penicillin antibiotics in vitro, in vivo, and as an heterologously expressed product. Its physiological role includes the modulation of beta-lactam resistance, biofilm formation and bacterial fitness under specific conditions. Evolutionary analysis suggests structural and functional conservation, pointing to its potential role in the adaptation of S. maltophilia to diverse and competitive environments.