期刊
FRONTIERS IN MICROBIOLOGY
卷 12, 期 -, 页码 -出版社
FRONTIERS MEDIA SA
DOI: 10.3389/fmicb.2021.639582
关键词
biofilm; lipoproteins; OMV; outer membrane vesicles; peptidoglycan; Pseudomonas aeruginosa
类别
资金
- Swedish Heart Lung Foundation [20180401]
- Swedish Research Council [2019-01053, 2018-06924]
- Swedish Society for Medical Research
- Sweden-America Foundation
- Royal Physiographical Society (Forssmans Foundation)
- Anna and Edwin Berger Foundation
- [NIH P30 DK089507]
- Swedish Research Council [2018-06924, 2019-01053] Funding Source: Swedish Research Council
The OmpA family proteins play crucial roles in cell morphology, membrane stability, and biofilm and outer membrane vesicle (OMV) formation in Pseudomonas aeruginosa. The lipoprotein from gene locus PA1041 was identified as a potential virulence factor that binds to peptidoglycan (PG) and influences the phenotype of the bacteria, leading to disordered biofilm formation. Mutants lacking this lipoprotein, designated as peptidoglycan-binding anchor (Pba), exhibited severe phenotypic changes, including enlarged periplasm spaces and increased release of OMV.
The outer membrane protein A (OmpA) family contains an evolutionary conserved domain that links the outer membrane in Gram-negative bacteria to the semi-rigid peptidoglycan (PG) layer. The clinically significant pathogen Pseudomonas aeruginosa carries several OmpA family proteins (OprF, OprL, PA0833, and PA1048) that share the PG-binding domain. These proteins are important for cell morphology, membrane stability, and biofilm and outer membrane vesicle (OMV) formation. In addition to other OmpAs, in silico analysis revealed that the putative outer membrane protein (OMP) with gene locus PA1041 is a lipoprotein with an OmpA domain and, hence, is a potential virulence factor. This study aimed to evaluate PA1041 as a PG-binding protein and describe its effect on the phenotype. Clinical strains were confirmed to contain the lipoprotein resulting from PA1041 expression with Western blot, and PG binding was verified in enzyme-linked immunosorbent assay (ELISA). By using a Sepharose bead-based ELISA, we found that the lipoprotein binds to meso-diaminopimelic acid (mDAP), an amino acid in the pentapeptide portion of PGs. The reference strain PAO1 and the corresponding transposon mutant PW2884 devoid of the lipoprotein were examined for phenotypic changes. Transmission electron microscopy revealed enlarged periplasm spaces near the cellular poles in the mutant. In addition, we observed an increased release of OMV, which could be confirmed by nanoparticle tracking analysis. Importantly, mutants without the lipoprotein produced a thick, but loose and unorganized, biofilm in flow cells. In conclusion, the lipoprotein from gene locus PA1041 tethers the outer membrane to the PG layer, and mutants are viable, but display severe phenotypic changes including disordered biofilm formation. Based upon the phenotype of the P. aeruginosa PW2884 mutant and the function of the protein, we designate the lipoprotein with locus tag PA1041 as peptidoglycan-binding anchor (Pba).
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