Interplay among membrane-bound lytic transglycosylase D1, the CreBC two-component regulatory system, the AmpNG-AmpDI-NagZ-AmpR regulatory circuit, and L1/L2 ?-lactamase expression in Stenotrophomonas maltophilia.

ABSTRACT: Lytic transglycosylases (LTs) are an important class of enzymes involved in peptidoglycan (PG) cleavage, with the concomitant formation of an intramolecular 1,6-anhydromuramoyl reaction product. There are six annotated LT genes in the Stenotrophomonas maltophilia genome, including genes for five membrane-bound LTs (mltA, mltB1, mltB2, mltD1, and mltD2) and a gene for soluble LT (slt). Six LTs of S. maltophilia KJ were systematically mutated, yielding the ?mltA, ?mltB1, ?mltB2, ?mltD1, ?mltD2, and ?slt mutants. Inactivation of mltD1 conferred a phenotype of elevated uninduced ?-lactamase activity. The underlying mechanism responsible for this phenotype was elucidated by the construction of several mutants and determination of ?-lactamase activity. The expression of the genes assayed was assessed by quantitative reverse transcriptase PCR and a promoter transcription fusion assay. The results demonstrate that ?mltD1 mutant-mediated L1/L2 ?-lactamase expression involved the creBC two-component regulatory system (TCS) and the ampNG-ampDI-nagZ-ampR regulatory circuit. The inactivation of mltD1 resulted in mltB1 and mltD2 upexpression in a creBC- and ampNG-dependent manner. The overexpressed MltB1 and MltD2 activity contributed to the expression of the L1/L2 ?-lactamase genes via the ampNG-ampDI-nagZ-ampR regulatory circuit. These findings reveal, for the first time, a linkage between LTs, the CreBC TCS, the ampNG-ampDI-nagZ-ampR regulatory circuit, and L1/L2 ?-lactamase expression in S. maltophilia.

SUBMITTER: Huang YW 

PROVIDER: S-EPMC4604389 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature