Distinct Roles of Major Peptidoglycan Recycling Enzymes in β-Lactamase Production in Shewanella oneidensis

Yin, Jianhua; Mao, Yinting; Ju, Lin; Jin, Miao; Sun, Yiyang; Jin, Shouguang; Gao, Haichun

doi:10.1128/aac.03238-14

Cited by 16 publications

(32 citation statements)

References 49 publications

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“…However, a homologue of AmpR is absent in S. oneidensis, and the impacts of major peptidoglycan recycling enzymes on blaA expression are distinct from the ampR-ampC paradigm. In particular, the loss of AmpG increases blaA expression, in contrast to the effect observed in previously studied cases (41).…”

contrasting

confidence: 52%

“…We have previously shown that expression of the blaA gene is substantially induced by AMP at high (Ͼ12.5 g/ml) but not low (Ͻ5 g/ml) levels in S. oneidensis (39,41). We speculated that an S. oneidensis strain harboring the E. coli lacZ gene under the control of the blaA promoter would form white and blue colonies on X-Gal plates in the presence of AMP at different levels.…”

Section: Resultsmentioning

confidence: 99%

“…BlaA ␤-lactamase activity assay. The specific BlaA ␤-lactamase activity was measured directly by nitrocefin hydrolysis as described previously (41). BlaA ␤-lactamase activity was expressed in nanomoles of nitrocefin hydrolyzed per minute per milligram of protein.…”

Section: Methodsmentioning

confidence: 99%

“…The activity of the P blaA promoter was assayed by use of a markerless integrative lacZ reporter system as described previously (41). The P blaA -lacZ fusion was integrated into the degenerated nrfCD locus as described before (47).…”

Section: Methodsmentioning

confidence: 99%

“…BlaA, along with its homologues from other Shewanella members, is proposed to be the progenitor of the carbapenem-hydrolyzing enzyme oxacillinase, which has been acquired by the clinically relevant Gram-negative species Acinetobacter baumannii and Klebsiella pneumoniae (34,37,40). Our previous studies showed that the blaA gene can be induced by ampicillin at high (Ͼ12.5 g/ml) but not low (Ͻ5 g/ml) levels, and its induction is also intimately linked to peptidoglycan recycling (39,41). However, a homologue of AmpR is absent in S. oneidensis, and the impacts of major peptidoglycan recycling enzymes on blaA expression are distinct from the ampR-ampC paradigm.…”

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confidence: 99%

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PBP1a/LpoA but Not PBP1b/LpoB Are Involved in Regulation of the Major β-Lactamase GeneblaAin Shewanella oneidensis

Yin

Sun

Mao

et al. 2015

Antimicrob Agents Chemother

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b ␤-Lactamase production is one of the most important strategies for Gram-negative bacteria to combat ␤-lactam antibiotics. Studies of the regulation of ␤-lactamase expression have largely been focused on the class C ␤-lactamase AmpC, whose induction by ␤-lactams requires LysR-type regulator AmpR and permease AmpG-dependent peptidoglycan recycling intermediates. In Shewanella, which is ubiquitous in aquatic environments and is a reservoir for antibiotic resistance, production of the class D ␤-lactamase BlaA confers bacteria with natural resistance to many ␤-lactams. Expression of the blaA gene in the genus representative Shewanella oneidensis is distinct from the AmpC paradigm because of the lack of an AmpR homologue and the presence of an additional AmpG-independent regulatory pathway. In this study, using transposon mutagenesis, we identify proteins that are involved in blaA regulation. Inactivation of mrcA and lpoA, which encode penicillin binding protein 1a (PBP1a) and its lipoprotein cofactor, LpoA, respectively, drastically enhances blaA expression in the absence of ␤-lactams. Although PBP1b and its cognate, LpoB, also exist in S. oneidensis, their roles in blaA induction are dispensable. We further show that the mrcA-mediated blaA expression is independent of AmpG. Beta-lactams are the most widely used antibiotics for treatment of bacterial infections. They mimic the dipeptide D-Ala-D-Ala and bind covalently to the serine active center of penicillin binding proteins (PBPs), resulting in inactivation of the latter, which are responsible for peptidoglycan synthesis and hydrolysis (1, 2). As one of the major approaches that evolved in bacteria to cope with the threat of ␤-lactams, ␤-lactamases are produced to directly degrade this group of antibiotics (3, 4). A variety of ␤-lactamases have been isolated, and their biochemical characteristics are intensively studied. Among them, some are found to be induced by ␤-lactams, but studies of the underlying regulatory mechanisms are largely focused on the class C ␤-lactamase AmpC in several Gram-negative bacteria, including Enterobacter cloacae, Citrobacter freundii, and Pseudomonas aeruginosa (5-13). Because of the discrepancy of the locations between ␤-lactam action and ␤-lactamase production, intermediate molecular signals must be produced to guide AmpC induction. Many studies have demonstrated that these molecular cues are derived from peptidoglycan recycling and that multiple proteins are involved in their production. AmpG is an inner membrane-bound permease that is responsible for the transportation of signal precursors, and its loss results in enhanced sensitivity to ␤-lactams because of the interruption of signal transduction (12-16). AmpR, a LysR family transcriptional regulator, alternates its conformation by binding to two different ligands to activate or repress the transcription of ampC (7,(17)(18)(19)(20)(21).As the primary targets for ␤-lactams, PBPs are no doubt potential candidates to sense the stress from antibiotics in the periplasm. PBPs are clas...

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confidence: 52%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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confidence: 99%

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