Authors: Rosa Guzmán-Hernández, Rosa Hernández-Vélez, Áraceli Contreras-Rodríguez...

Topics: Humans; Polymerase Chain Reaction; Vibrio

PubMed: 27905630
DOI: 10.4067/S0716-10182016000400011

Authors: Yuanming Huang, Yu Han, Zhenpeng Li...

is a halophilic Gram-negative bacterium regarded as an emerging unusual enteric pathogen of increasing public health concern. Our previous work has identified two type VI secretion systems (T6SSs) in , VflT6SS1, and VflT6SS2, and the latter is functional in mediating interbacterial competitiveness. However, its antibacterial effectors remain to be clarified. In this work, we focused on a new potential effector/immunity pair TssI2/TsiI2. Bioinformatics analysis revealed that the C-terminal domain of TssI2 belongs to a widespread family of pesticin, and its antibacterial toxicity and corresponding protection by TsiI2 were proved via bacterial killing assays, and their action sites were localized to the periplasm of bacterial cells. The interaction of TssI2 and TsiI2 was demonstrated by the bacterial adenylate cyclase two-hybrid, protein pull-down and isothermal titration calorimetry assays. Site-directed mutagenesis demonstrated that, in addition to Glu-844, Thr-863, and Asp-869, which correspond to three reported residues in pesticin of , additional residues including Phe-837, Gly-845, Tyr-851, Gly-867, Gln-963, Trp-975, and Arg-1000 were also proved to be crucial to the bactericidal activity of TssI2. Muramidase/lysozyme-related peptidoglycan (PG) hydrolase activities of TssI2 and its variants were validated with permeabilized cells and purified PG substrate. Based on sequence homologies at C-terminals in various isolates, TssI2 was subdivided into five clusters (12-22% identity among them), and the antibacterial activities of representative effectors from other four Clusters were also confirmed through periplasmic over-expression in host. Two selected cognate immunities were proved to confer protection against the toxicities of their effectors. Additionally, TsiI2, which belongs to Cluster I, exhibited cross-protection to effector from Cluster V. Together, current findings expand our knowledge of the diversity and consistency of evolved VgrG effectors in and on how VflT6SS2 mediates a competitive advantage to gain a better survival.

Topics: Type VI Secretion Systems; Periplasm; Muramidase; Escherichia coli; Peptidoglycan; Adenylyl Cyclases; Gastrointestinal Microbiome; Bacterial Proteins; Anti-Bacterial Agents

PubMed: 36288406
DOI: 10.1080/19490976.2022.2136460

Review

Authors: Thandavarayan Ramamurthy, Goutam Chowdhury, Gururaja P Pazhani...

Vibrio fluvialis is a pathogen commonly found in coastal environs. Considering recent increase in numbers of diarrheal outbreaks and sporadic extraintestinal cases, V. fluvialis has been considered as an emerging pathogen. Though this pathogen can be easily isolated by existing culture methods, its identification is still a challenging problem due to close phenotypic resemblance either with Vibrio cholerae or Aeromonas spp. However, using molecular tools, it is easy to identify V. fluvialis from clinical and different environmental samples. Many putative virulence factors have been reported, but its mechanisms of pathogenesis and survival fitness in the environment are yet to be explored. This chapter covers some of the major discoveries that have been made to understand the importance of V. fluvialis.

PubMed: 24653717
DOI: 10.3389/fmicb.2014.00091

Authors: Anran Zhang, Yue Xiao, Yu Han...

The type VI secretion system (T6SS) is essential for Gram-negative bacteria to antagonize a wide variety of prokaryotic and eukaryotic competitors and thus gain survival advantages. Two sets of T6SS have been found in , namely VflT6SS1 and VflT6SS2, among which VflT6SS2 is functionally expressed. The CqsA/LuxS-HapR quorum sensing (QS) system with CAI-1 and AI-2 as signal molecules can regulate VflT6SS2 by regulators LuxO and HapR, with LuxO repressing while HapR activating VflT6SS2. Quorum regulatory small RNAs (Qrr sRNAs) are Hfq-dependent -encoded sRNAs that control quorum sensing. In , Qrr sRNAs have not been characterized and their regulatory function is unknown. In this study, we first identified four Qrr sRNAs in and demonstrated that these Qrr sRNAs are regulated by LuxO and involved in the modulation of VflT6SS2 function. On the one hand, Qrr sRNAs act on HapR, the activator of both the major and the auxiliary clusters of VflT6SS2, and then indirectly repress VflT6SS2. On the other hand, they directly repress VflT6SS2 by acting on 2 and 2_a, the first gene of the major cluster and the highly transcriptional one among the two units of the first auxiliary cluster, respectively. Our results give insights into the role of Qrr sRNAs in CAI-1/AI-2 based QS and VflT6SS2 modulation in . and further enhance understandings of the network between QS and T6SS regulation in species.

Topics: Vibrio; Quorum Sensing; Gene Expression Regulation, Bacterial; Type VI Secretion Systems; Bacterial Proteins; RNA, Bacterial; RNA, Small Untranslated

PubMed: 39193622
DOI: 10.1080/22221751.2024.2396872

Authors: Yuanming Huang, Pengcheng Du, Meng Zhao...

is an emerging foodborne pathogen of increasing public health concern. The mechanism(s) that contribute to the bacterial survival and disease are still poorly understood. In other bacterial species, type VI secretion systems (T6SSs) are known to contribute to bacterial pathogenicity by exerting toxic effects on host cells or competing bacterial species. In this study, we characterized the genetic organization and prevalence of two T6SS gene clusters (VflT6SS1 and VflT6SS2) in . VflT6SS2 harbors three "orphan" modules and was more prevalent than VflT6SS1 in our isolates. We showed that VflT6SS2 is functionally active under low (25°C) and warm (30°C) temperatures by detecting the secretion of a T6SS substrate, Hcp. This finding suggests that VflT6SS2 may play an important role in the survival of the bacterium in the aquatic environment. The secretion of Hcp is growth phase-dependent and occurs in a narrow range of the growth phase (OD from 1.0 to 2.0). Osmolarity also regulates the function of VflT6SS2, as evidenced by our finding that increasing salinity (from 170 to 855 mM of NaCl) and exposure to high osmolarity KCl, sucrose, trehalose, or mannitol (equivalent to 340 mM of NaCl) induced significant secretion of Hcp under growth at 30°C. Furthermore, we found that although VflT6SS2 was inactive at a higher temperature (37°C), it became activated at this temperature if higher salinity conditions were present (from 513 to 855 mM of NaCl), indicating that it may be able to function under certain conditions in the infected host. Finally, we showed that the functional expression of VflT6SS2 is associated with anti-bacterial activity. This activity is Hcp-dependent and requires , a transcriptional regulator of T6SS. In sum, our study demonstrates that VflT6SS2 provides with an enhanced competitive fitness in the marine environment, and its activity is regulated by environmental signals, such as temperature and osmolarity.

PubMed: 28424671
DOI: 10.3389/fmicb.2017.00528

Authors: Jingjing Pan, Meng Zhao, Yuanming Huang...

, an emerging foodborne pathogen of increasing public health concern, contains two distinct gene clusters encoding type VI secretion system (T6SS), the most newly discovered secretion pathway in Gram-negative bacteria. Previously we have shown that one of the two T6SS clusters, namely VflT6SS2, is active and associates with anti-bacterial activity. However, how its activity is regulated is not completely understood. Here, we report that the global regulator integration host factor (IHF) positively modulates the expression and thus the function of VflT6SS2 through co-regulating its major cluster and 22 (also known as ) orphan clusters. Specifically, reporter gene activity assay showed that IHF transactivates the major and orphan clusters of VflT6SS2, while deletion of either or , the genes encoding the IHF subunits, decreased their promoter activities and mRNA levels of 2, , and 2 for the selected major cluster genes and 2 and 2 for the selected orphan cluster genes. Subsequently, the direct bindings of IHF to the promoter regions of the major and orphan clusters were confirmed by electrophoretic mobility shift assay (EMSA). Site-directed mutagenesis combined with reporter gene activity assay or EMSA pinpointed the exact binding sites of IHF in the major and orphan cluster promoters, with two sites in the major cluster promoter, consisting with its two observed shifted bands in EMSA. Functional studies showed that the expression and secretion of hemolysin-coregulated protein (Hcp) and the VflT6SS2-mediated antibacterial virulence were severely abrogated in the deletion mutants of Δ and Δ, but restored when their trans-complemented plasmids were introduced, suggesting that IHF mostly contributes to environmental survival of . by directly binding and modulating the transactivity and function of VflT6SS2.

PubMed: 29867866
DOI: 10.3389/fmicb.2018.00962

Review

Authors: Etinosa O Igbinosa, Anthony I Okoh

In developing countries, the fraction of treated wastewater effluents being discharged into watersheds have increased over the period of time, which have led to the deteriorations of the qualities of major rivers in developing nations. Consequently, high densities of disease causing bacteria in the watersheds are regularly reported including incidences of emerging Vibrio fluvialis. Vibrio fluvialis infection remains among those infectious diseases posing a potentially serious threat to public health. This paper addresses the epidemiology of this pathogen; pathogenesis of its disease; and its clinical manifestations in humans.

Topics: Public Health Practice; Vibrio; Vibrio Infections; Water Microbiology

PubMed: 21139853
DOI: 10.3390/ijerph7103628

Authors: Hin-Chung Wong, Li-Li Chen, Chung-Ming Yu...

Pathogenic vibrios are important etiologic agents in tropical regions and have been frequently recovered from seafoods and aquacultured foods. A number of psychrotrophic vibrios were isolated and selected from frozen seafoods and their survivals in tryptic soy broth (TSB) at 4°C and -30°C were studied. These psychrotrophic strains showed good survival at low temperatures and could probably enhance the risk of vibrios in frozen foods. Vibrio mimicus 70 and 198, Vibrio fluvialis 52 and Vibrio parahaemolyticus 205 survived well at 10°C, 4°C and -30°C, while the non-cold fitter V. fluvialis 28 was completely inactivated in the test periods. These strains were not heat resistant and could be easily inactivated by heat treatment. Effect of phosphates may be different for. various Vibrio species at low temperatures. Survival of V. parahaemolyticus 205 was significantly protected by the heated metaphosphate at 4°C by lowering the lethality of cold injured cells but not by increasing the level of uninjured viable cells. Pyrophosphate was inhibitory to this V. parahaemolyticus strain at -30°C.

PubMed: 31121705
DOI: 10.4315/0362-028X-57.7.607

Authors: Beiwen Zheng, Xiawei Jiang, Hong Cheng...

Vibrio fluvialis is recognized as an emerging pathogen. However, not much is known about the mechanism of its pathogenesis, and its adaptation to a special niche such as the gall bladder. Here we describe two V. fluvialis strains that cause acute cholecystitis. It is noteworthy that both strains were susceptible to all antibiotics tested, which is in contrast to previous studies, suggesting substantial genetic diversity among V. fluvialis isolates. In agreement with their survival and growth in the gall bladder, the genomes of strains 12605 and 3663 contain a considerable number of genes that confer resistance to bile, including toxR, omp U, tolC, cmeABC, rlpB, yrbK, rpoS, damX and gltK. Furthermore, integrative and conjugative elements (ICEs), virulence factors and prophage regions were also detected in strains 12605 and 3663, reflecting their flexibility in recombination during the evolution of pathogenicity. Comparative analysis of nine available genomes of V. fluvialis revealed a core genome consisting of 3,147 genes. Our results highlight the association of V. fluvialis with a rare disease profile and shed light on the evolution of pathogenesis and niche adaptation of V. fluvialis.

Topics: Bacterial Proteins; Bile; Female; Genome, Bacterial; Humans; Male; Species Specificity; Vibrio; Virulence; Virulence Factors

PubMed: 28928424
DOI: 10.1038/s41598-017-12304-8

Authors: Pu Liang, Xiaoying Cui, Xiaoli Du...

BACKGROUND

Vibrio fluvialis is considered to be an emerging foodborne pathogen and has been becoming a high human public health hazard all over the world, especially in coastal areas of developing countries and regions with poor sanitation. The distribution of virulence factors, microbiological and molecular epidemiological features of V. fluvialis isolates in China remains to be examined.

METHODS AND RESULTS

PCR targeted at the virulence determinants and phenotype tests including metabolism, virulence and antibiotic susceptibility were performed. Pulsed-field gel electrophoresis (PFGE) analysis was used to access the relatedness of isolates. A strain with deletion of the arginine dihydrolase system was first reported and proved in molecular level by PCR. Virulence genes vfh, hupO and vfpA were detected in all strains, the ability to produce hemolysin, cytotxin, protease and biofilm formation varied with strains. High resistance rate to β-lactams, azithromycin and sulfamethoxazole were observed. Twenty-seven percent of test strains showed resistant to two and three antibiotics. PFGE analysis demonstrated great genetic heterogeneity of test V. fluvialis strains.

CONCLUSION

This study evaluated firstly the biological characteristics and molecular epidemiological features of V. fluvialis in China. Some uncommon biochemical characteristics were found. Virulence genes were widely distributed in the isolates from patient and seafood sources, and the occurrence of virulence phenotypes varied with strains. Continued and enhanced laboratory based-surveillance is needed in the future together with systematically collection of the epidemiological information of the cases or the outbreaks.

PubMed: 23522652
DOI: 10.1186/1757-4749-5-6