Identification of a new hemolysin from diarrheal isolate SSU of<i>Aeromonas hydrophila</i>

Erova, Tatiana E.; Sha, Jian; Horneman, Amy J.; Borchardt, Mark A.; Khajanchi, Bijay K.; Fadl, Amin A.; Chopra, Ashok K.

doi:10.1111/j.1574-6968.2007.00895.x

Cited by 30 publications

(13 citation statements)

References 52 publications

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“…Also, we did not observe any differences in the hemolytic and/or cytotoxic activities in culture supernatants of Aeromonas WT and its vacB mutant strain, indicating that VacB did not modulate the activities of Act and the other hemolysins (e.g., HlyA) or cytotoxins that we recently described in A. hydrophila SSU (16).…”

Section: Resultsmentioning

confidence: 75%

Cold Shock Exoribonuclease R (VacB) Is Involved in Aeromonas hydrophila Pathogenesis

Erova¹,

Kosykh

Fadl³

et al. 2008

J Bacteriol

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In this study, we cloned and sequenced a virulence-associated gene (vacB) from a clinical isolate SSU of Aeromonas hydrophila. We identified this gene based on our recently annotated genome sequence of the environmental isolate ATCC 7966 T of A. hydrophila and the vacB gene of Shigella flexneri. The A. hydrophila VacB protein contained 798 amino acid residues, had a molecular mass of 90.5 kDa, and exhibited an exoribonuclease (RNase R) activity. The RNase R of A. hydrophila was a cold-shock protein and was required for bacterial growth at low temperature. The vacB isogenic mutant, which we developed by homologous recombination using marker exchange mutagenesis, was unable to grow at 4°C. In contrast, the wild-type (WT) A. hydrophila exhibited significant growth at this low temperature. Importantly, the vacB mutant was not defective in growth at 37°C. The vacB mutant also exhibited reduced motility, and these growth and motility phenotype defects were restored after complementation of the vacB mutant. The A. hydrophila RNase R-lacking strain was found to be less virulent in a mouse lethality model (70% survival) when given by the intraperitoneal route at as two 50% lethal doses (LD 50 ). On the other hand, the WT and complemented strains of A. hydrophila caused 80 to 90% of the mice to succumb to infection at the same LD 50 dose. Overall, this is the first report demonstrating the role of RNase R in modulating the expression of A. hydrophila virulence.A human diarrheal isolate SSU of Aeromonas hydrophila possesses various pathogenic mechanisms that contribute to the overall virulence of this bacterium in the host. Most importantly, our laboratory has described type II, type III, and type VI secretion system effector proteins that are involved in the disease state (gastroenteritis or septicemia) in animal models (11,15,17,21,32,(44)(45)(46)48). However, to better understand the full virulence potential of any pathogen, it is important to identify new pathogenic factors and/or mechanisms that could be involved in their virulence. This is crucial since the expression of different virulence genes could be contributing factors leading to disease depending upon the anatomical niche where the organisms colonize and the environment in those regions which dictates the differential expression of genes (18).Studies by Tobe et al. (50) identified a novel chromosomal gene, vacB, which was required for the production of S. flexneri virulence factors (e.g., IpaB, IpaC, IpaD, and VirG) from the large plasmid (230 kb) of this microorganism. More recently, it was shown that the vacB gene in S. flexneri and Escherichia coli strains encoded the 3Ј-5Ј exoribonuclease RNase R (10). The deduced size of VacB (virulence-associated) protein is approximately 92 kDa, and it is located at 95 min on the E. coli chromosome, a position consistent with the earlier mapping studies of the gene encoding RNase R (10). These investigators provided evidence that RNase R has an essential cell function, in addition to its role in bacterial virulence, an...

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Section: Resultsmentioning

confidence: 75%

Cold Shock Exoribonuclease R (VacB) Is Involved in Aeromonas hydrophila Pathogenesis

Erova¹,

Kosykh

Fadl³

et al. 2008

J Bacteriol

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“…Hemolysins and related proteins containing cystathionine β synthase (CBS) domains are bacterial toxins that function by assembling identical subunits into a membrane-spanning pore [25]. The molecular mass of bacterial hemolysins ranges from 49 to 60 kDa [25][26][27][28][29]. We have demonstrated presence of a prominent protein band of approximately 50 kDa in extracellular protein fraction of this pathogenic isolate which indicates the possible presence of the bacterial toxin, hemolysin [26].…”

Section: Discussionmentioning

confidence: 99%

“…Hemolytic proteins are commonly isolated from pathogenic bacteria, and β-hemolysins are one of the important bacterial virulence factors. Hemolysins and related proteins containing cystathionine β synthase (CBS) domains are bacterial toxins that function by assembling identical subunits into a membrane-spanning pore [25]. The molecular mass of bacterial hemolysins ranges from 49 to 60 kDa [25][26][27][28][29].…”

Section: Discussionmentioning

confidence: 99%

Hemolysin, Protease, and EPS Producing PathogenicAeromonas hydrophilaStrain An4 Shows Antibacterial Activity against Marine Bacterial Fish Pathogens

Pandey

Naik

Dubey

2010

Journal of Marine Biology

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A pathogenic Aeromonas hydrophila strain An4 was isolated from marine catfish and characterized with reference to its proteolytic and hemolytic activity along with SDS-PAGE profile (sodium dodecyl sulphate-Polyacrylamide gel electrophoresis) of ECPs (extracellular proteins) showing hemolysin (approximately 50 kDa). Agar well diffusion assay using crude cell extract of the bacterial isolate clearly demonstrated antibacterial activity against indicator pathogenic bacteria, Staphylococcus arlettae strain An1, Acinetobacter sp. strain An2, Vibrio parahaemolyticus strain An3, and Alteromonas aurentia SE3 showing inhibitory zone >10 mm well comparable to common antibiotics. Further GC-MS analysis of crude cell extract revealed several metabolites, namely, phenolics, pyrrolo-pyrazines, pyrrolo-pyridine, and butylated hydroxytoluene (well-known antimicrobials). Characterization of EPS using FTIR indicated presence of several protein-related amine and amide groups along with peaks corresponding to carboxylic and phenyl rings which may be attributed to its virulent and antibacterial properties, respectively. Besides hemolysin, EPS, and protease, Aeromonas hydrophila strain An4 also produced several antibacterial metabolites.

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“…For example, the prototypical diarrheal isolate SSU contains at least four distinct factors with enterotoxigenic capabilities in vitro, namely, Hly, Act, Alt, and Ast (71). What role does each or any of these play in diarrhea, and is this gene assortment representative of other fecal isolates representing diverse species associated with gastroenteritis?…”

Section: Organotrophic Diseasementioning

confidence: 99%

The GenusAeromonas: Taxonomy, Pathogenicity, and Infection

2010

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SUMMARY Over the past decade, the genus Aeromonas has undergone a number of significant changes of practical importance to clinical microbiologists and scientists alike. In parallel with the molecular revolution in microbiology, several new species have been identified on a phylogenetic basis, and the genome of the type species, A. hydrophila ATCC 7966, has been sequenced. In addition to established disease associations, Aeromonas has been shown to be a significant cause of infections associated with natural disasters (hurricanes, tsunamis, and earthquakes) and has been linked to emerging or new illnesses, including near-drowning events, prostatitis, and hemolytic-uremic syndrome. Despite these achievements, issues still remain regarding the role that Aeromonas plays in bacterial gastroenteritis, the extent to which species identification should be attempted in the clinical laboratory, and laboratory reporting of test results from contaminated body sites containing aeromonads. This article provides an extensive review of these topics, in addition to others, such as taxonomic issues, microbial pathogenicity, and antimicrobial resistance markers.

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Identification of a new hemolysin from diarrheal isolate SSU ofAeromonas hydrophila

Cited by 30 publications

References 52 publications

Cold Shock Exoribonuclease R (VacB) Is Involved in Aeromonas hydrophila Pathogenesis

Cold Shock Exoribonuclease R (VacB) Is Involved in Aeromonas hydrophila Pathogenesis

Hemolysin, Protease, and EPS Producing PathogenicAeromonas hydrophilaStrain An4 Shows Antibacterial Activity against Marine Bacterial Fish Pathogens

The GenusAeromonas: Taxonomy, Pathogenicity, and Infection

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