Characterization of PBP2 in Stenotrophomonas maltophilia

• Main Authors: Yu Wang, 王瑀
• Other Authors: Tsuey-Ching Yang
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/18198793524053021214

碩士 === 國立陽明大學 === 醫學生物技術暨檢驗學系 === 104 === Penicillin-binding proteins (PBPs) are a group of proteins that are characterized by their affinity toward β-lactam antibiotic, and involved in the final stages of the synthesis of peptidoglycan, a major component of bacterial cell walls. There are seven annotated PBP genes in the S. maltophilia genome, including five genes encoding high-molecular-weight PBPs (mrcA, mrcB, pbpC, mrdA, and ftsI) and two gene encoding low-molecular-weight PBPs (dacB and dacC). This study aimed to investigate the linkage of mrdA inactivation to β-lactamase expression, and β-lactams resistance, and physiological functions in S. maltophilia KJ. Of six constructed PBP single mutants, KJmrcA, KJmrcB, KJpbpC, KJmrdA, KJdacB, and KJdacC, KJmrcA and KJmrdA displayed elevated basal-level β-lactamase activities. Furthermore, the increment of basal-level -lactamase activities was additive when mrcA and mrdA were simultaneously inactivated. The underlying mechanism for mrdA-mediated basal-level -lactamase activity increment was elucidated by an array of mutants construction and -lactamase activity determined. The results demonstrated that ΔmrdA-mediated basal β-lactamase activity increment relies on AmpNG, NagZ, AmpR, but less relates to CreBC two-component regulatory system. Inactivation of mrdA little affected the susceptibility of S. maltophilia KJ toward -lactams. The impact of mrdA inactivation on physiological functions was further assessed, including bacteria growth, morphology, membrane integrity, swimming, oxidative stress tolerance, and secreted protease activity. The results showed that (i) Compared to wild-type KJ, KJmrdA grew slower and exhibited a spherical morphology, (ii) Inactivation of mrdA compromised the membrane tolerance toward Triton X-100 and increased the membrane uptaking potential for positively charged substances, (iii) Loss of PBP2 decreased swimming motility, and secreted protease activity, and increased H2O2 and menadione susceptibilities.