Class A Penicillin-Binding Protein C Is Responsible for Stress Response by Regulation of Peptidoglycan Assembly in Clavibacter michiganensis

Chen, Xing; Li, Yao; Bai, Kaihong; Gu, Meng; Xu, Xiaoli; Jiang, Na; Chen, Yu; Li, Jianqiang; Luo, Laixin

doi:10.1128/spectrum.01816-22

Cited by 4 publications

(3 citation statements)

References 46 publications

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“…Regarding cell morphology, the △ pbpC mutants were not rod-shaped but instead had a thinner cell wall, as observed by transmission electron microscopy and atomic force microscopy. The △ pbpC mutants of C. michiganensis strain BT0505 were more sensitive to lysozymes and environmental stress response, such as ultrasonication and Cu 2+ treatment [ 17 , 48 ]. However, the mechanism of these phenotypic changes in the △ pbpC mutants associated with their increased virulence in tomato seedlings was firstly demonstrated in this study.…”

Section: Discussionmentioning

confidence: 99%

“…Two strains of C. michiganensis GS12102 and BT0505, which differ in their geographic origin and plasmid number, were used to prepare △ pbpC mutants and a series of derived strains. It was revealed that the thickness of the cell wall peptidoglycan layer of strain BT0505 △ pbpC mutants is thinner and the number of cross-links is decreased compared with those of the wild-type strain [ 48 ]. Accordingly, a lack of pbpC in C. michiganensis appeared to result in a more fragile cell wall.…”

Section: Discussionmentioning

confidence: 99%

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Deletion of pbpC Enhances Bacterial Pathogenicity on Tomato by Affecting Biofilm Formation, Exopolysaccharides Production, and Exoenzyme Activities in Clavibacter michiganensis

Chen

et al. 2023

IJMS

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Penicillin-binding proteins (PBPs) are considered essential for bacterial peptidoglycan biosynthesis and cell wall assembly. Clavibacter michiganensis is a representative Gram-positive bacterial species that causes bacterial canker in tomato. pbpC plays a significant role in maintaining cell morphological characteristics and stress responses in C. michiganensis. The current study demonstrated that the deletion of pbpC commonly enhances bacterial pathogenicity in C. michiganensis and revealed the mechanisms through which this occurs. The expression of interrelated virulence genes, including celA, xysA, xysB, and pelA, were significantly upregulated in △pbpC mutants. Compared with those in wild-type strains, exoenzyme activities, the formation of biofilm, and the production of exopolysaccharides (EPS) were significantly increased in △pbpC mutants. It is noteworthy that EPS were responsible for the enhancement in bacterial pathogenicity, with the degree of necrotic tomato stem cankers intensifying with the injection of a gradient of EPS from C. michiganensis. These findings highlight new insights into the role of pbpC affecting bacterial pathogenicity, with an emphasis on EPS, advancing the current understanding of phytopathogenic infection strategies for Gram-positive bacteria.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Deletion of pbpC Enhances Bacterial Pathogenicity on Tomato by Affecting Biofilm Formation, Exopolysaccharides Production, and Exoenzyme Activities in Clavibacter michiganensis

Chen

et al. 2023

IJMS

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“…PBPs are classified into two main categories based on their molecular weight: high-molecular-weight (HMW) PBPs and low-molecular-weight (LMW) PBPs [14]. Class A PBPs are HMW PBPs with molecular weights typically exceeding 100 kDa [15]. They are responsible for crosslinking peptidoglycans in the cell wall and exhibit both transglycosylase and transpeptidase activities [16].…”

Section: Introductionmentioning

confidence: 99%

Structural Insights into the Penicillin-Binding Protein 4 (DacB) from Mycobacterium tuberculosis

Kang,

Kim

2024

IJMS

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Mycobacterium tuberculosis, a major cause of mortality from a single infectious agent, possesses a remarkable mycobacterial cell envelope. Penicillin-Binding Proteins (PBPs) are a family of bacterial enzymes involved in the biosynthesis of peptidoglycan. PBP4 (DacB) from M. tuberculosis (MtbPBP4) has been known to function as a carboxypeptidase, and the role and significance of carboxypeptidases as targets for anti-tuberculosis drugs or antibiotics have been extensively investigated over the past decade. However, their precise involvement remains incompletely understood. In this study, we employed predictive modeling and analyzed the three-dimensional structure of MtbPBP4. Interestingly, MtbPBP4 displayed a distinct domain structure compared to its homologs. Docking studies with meropenem verified the presence of active site residues conserved in PBPs. These findings establish a structural foundation for comprehending the molecular function of MtbPBP4 and offer a platform for the exploration of novel antibiotics.

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Unexpected vulnerability of Enterococcus faecium to polymyxin B under anaerobic condition

Son,

Kim,

Kim

et al. 2024

Gut Microbes

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Gram-positive Enterococcus faecium exhibited higher susceptibility (>4-fold) to polymyxin B (PMB), the canonical antimicrobial peptide against Gram-negative bacteria, under anaerobic condition than aerobic condition. Anaerobically grown E. faecium exhibited high vulnerability to PMB, leading to alteration of cell surface and morphology, as observed based on their high dansyl-PMB affinity (>2.9-fold), a proportion (>8.5-fold) of propidium iodide-stained cells, and observation of scanning electron microscopy results. Interestingly, our transcriptomic and chemical analyses revealed that enterocin B, produced anaerobically, imposes a burden on the cellular envelope when cells are exposed to PMB. This scenario was also supported by PMB susceptibility tests and killing curves, which showed that Δ entB knockout mutant cells were more resistant to PMB (32 µg/mL) compared to wild-type cells (4 µg/mL) under anaerobic condition. Fluorescent D-amino acid and BOCILLIN™-fluorescent profiling of transpeptidase activities in Δ entB mutant cells under anaerobic condition revealed similar levels of activity to those observed in WT cells under aerobic condition. The high level of secreted bacteriocins in WT under anaerobic condition likely led to significant membrane depolarization and loosening of the peptidoglycan layer, making the cells more permeable to PMB. Overall, our findings suggest that anaerobically produced bacteriocins, in conjunction with PMB, contribute to the killing of E. faecium by destabilizing its cell envelope.

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Class A Penicillin-Binding Protein C Is Responsible for Stress Response by Regulation of Peptidoglycan Assembly in Clavibacter michiganensis

Abstract: Peptidoglycan of cell walls in bacteria is a cross-linked and meshlike scaffold that provides strength to withstand the external pressure. The increased cross-linkage in peptidoglycan and altered structure in VBNC cells endowed the cell wall more resistant to adversities.

Cited by 4 publications

References 46 publications

Deletion of pbpC Enhances Bacterial Pathogenicity on Tomato by Affecting Biofilm Formation, Exopolysaccharides Production, and Exoenzyme Activities in Clavibacter michiganensis

Deletion of pbpC Enhances Bacterial Pathogenicity on Tomato by Affecting Biofilm Formation, Exopolysaccharides Production, and Exoenzyme Activities in Clavibacter michiganensis

Structural Insights into the Penicillin-Binding Protein 4 (DacB) from Mycobacterium tuberculosis

Unexpected vulnerability of Enterococcus faecium to polymyxin B under anaerobic condition

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