Lack of Outer Membrane Protein A Enhances the Release of Outer Membrane Vesicles and Survival ofVibrio choleraeand Suppresses Viability ofAcanthamoeba castellanii

Abstract

Vibrio cholerae, the causative agent of the diarrhoeal disease cholera, survives in aquatic environments. The bacterium has developed a survival strategy to grow and survive inside Acanthamoeba castellanii. It has been shown that V. cholerae expresses outer membrane proteins as virulence factors playing a role in the adherence to interacted host cells. This study examined the role of outer membrane protein A (OmpA) and outer membrane vesicles (OMVs) in survival of V. cholerae alone and during its interaction with A. castellanii. The results showed that an OmpA mutant of V. cholerae survived longer than wild-type V. cholerae when cultivated alone. Cocultivation with A. castellanii enhanced the survival of both bacterial strains and OmpA protein exhibited no effect on attachment, engulfment, and survival inside the amoebae. However, cocultivation of the OmpA mutant of V. cholerae decreased the viability of A. castellanii and this bacterial strain released more OMVs than wild-type V. cholerae. Surprisingly, treatment of amoeba cells with OMVs isolated from the OmpA mutant significantly decreased viable counts of the amoeba cells. In conclusion, the results might highlight a regulating rule for OmpA in survival of V. cholerae and OMVs as a potent virulence factor for this bacterium towards eukaryotes in the environment.

Modulation of bacterial outer membrane vesicle production by envelope structure and content

“…Previous genetic and crosslinking studies have shown that there is an interaction between Lpp and OmpA [ 30 , 44 , 45 ], an OM β-barrel protein with a periplasmic PG-interaction domain [ 46 , 47 ]. A deletion in ompA , which encodes OmpA, resulted in ~26-fold hypervesiculation (Figure 4 C), consistent with the phenotypes of the Δ ompA Salmonella and Vibrio cholerae mutants [ 29 , 48 ]. We tested if the nlpA deletion was epistatic to Δ ompA.…”

The Importance of Porins and β-Lactamase in Outer Membrane Vesicles on the Hydrolysis of β-Lactam Antibiotics

“…A deletion in ompA, encoding an outer membrane β-barrel protein with a periplasmic peptidoglycan-interaction domain resulted in a 26-fold hypervesiculation in E. coli mutant [35]. Valeru et al (2014) showed a 3-fold increase in the level of production of OMVs by an OmpA mutant of Vibrio cholerae compared to the wild-type [36]. In line with these findings, our results showed that a lack of porins enhances the release of OMVs (Figure 3).…”

Campylobacter–Acanthamoeba interactions

“…Although C. jejuni strain 11168 has a putative OmpA protein (Cj0599), CadF shares the highest similarity with OmpA from E. coli. In contrast, it was shown that in V. cholerae the lack of outermembrane protein OmpA suppresses Acanthamoeba viability, and its survival inside this host is enhanced in the absence of this protein (Valeru et al, 2014). Instead, the transcriptional regulator ToxR, which modulates expression of the outer-membrane proteins OmpU and OmpT in V. cholerae, was found to be necessary for the survival of this pathogen within amoebae (Valeru et al, 2012), but no potential orthologues of these proteins could be found in C. jejuni.…”