Sun Nyunt Wai

My research can be divided in to two main research areas of interest. 1. Molecular mechanisms controlling biofilm formation, virulence factor expression, rugose switching. 2. The relationship between the release of outer membrane vesicles and secretion of virulence factors in Vibrio cholerae and enterobacteria.

Project 1.Cholera is a serious epidemic disease that has
killed millions of people and continues to be a major health
problem worldwide. The bacterium Vibrio cholerae is a motile, gram-negative curved rod with a single polar flagellum. It was discovered that V. cholerae O1 from the Peru epidemic was able shift to a phenotype having wrinkled or rugose colony morphology. It is suggested that the V. cholerae rugose phenotype represent a fully virulent survival form of the organism that can persist in the presence of free chlorine. However, the relationships between the phenotypic and genetic characteristics associated with rugose morphology, and their relative importance in pathogenicity still remained to be identified.

We have isolated the rugose variants of V. cholerae O1 strain TSI-4 and V. cholerae O139 MO10 from starvation medium and determined EPS expression on the surface of the rugose strains by polycationic ferritin-labeled thin-section electron microscopy. We found that they produced a continuous biofilm on the colonized surface and that the polysaccharide may have a role in resistance to osmotic and oxidative stress. While there seem to be a role for quorum sensing in regulation of virulence properties in such pathogens the actual controlling mechanisms are far from understood.

Project 2. Outer membrane vesicles have been broadly defined as spherical fragments of the bacterial membrane and are produce by a wide variety of Gram-negative bacteria during normal growth. Vesicles have been proposed to play a role in several virulence mechanisms: periplasmic enzyme delivery DNA transport and evasion of the immune system. Our work also showed that the cholera toxin-like toxin LT (heat labile toxin) from enterotoxigenic Escherichia coli (ETEC) is excreted via outer membrane vesicles.

We have recently studied a cytotoxic protein (ClyA) in E. coli that we found was exported through outer membrane vesicles. Furthermore, the cytotoxin was acting much more potent on human target cells when present in vesicles in com-parison with the purified cytotoxin (Wai et al. 2003).We investigated the vesicles by electron microscopy and atomic force microscopy and by biochemical approaches. According to our present results, vesicles can be proposed to play a role in export and activation of the virulence factors to the external environment.

Publications in Pubmed

Publications

Author

Title

Year sorteringsordning

Fulltext

Vdovikova, Svitlana
Luhr, Morten
Szalai, Paula; et al.

A Novel Role of Listeria monocytogenes Membrane Vesicles in Inhibition of Autophagy and Cell Death
Frontiers in Cellular and Infection Microbiology, 7

2017

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Bitar, Aziz
De, Rituparna
Melgar, Silvia; et al.

Induction of immunomodulatory miR-146a and miR-155 in small intestinal epithelium of Vibrio cholerae infected patients at acute stage of cholera
PLoS ONE, 12(3)

2017

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Tobias, Joshua
Lebens, Michael
Wai, Sun Nyunt; et al.

Surface expression of Helicobacter pylori HpaA adhesion antigen on Vibrio cholerae, enhanced by co-expressed enterotoxigenic Escherichia coli fimbrial antigens
Microbial Pathogenesis, 105: 177-184

2017

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Aung, Kyaw Min
Sjöström, Annika E
von Pawel-Rammingen, Ulrich; et al.

Naturally Occurring IgG Antibodies Provide Innate Protection against Vibrio cholerae Bacteremia by Recognition of the Outer Membrane Protein U
Journal of Innate Immunity, 8(3): 269-283

2016

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Resch, Ulrike
Tsatsaronis, James Anthony
Le Rhun, Anais; et al.

A Two-Component Regulatory System Impacts Extracellular Membrane-Derived Vesicle Production in Group A Streptococcus
mBio, 7(6)

2016

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Song, Tianyan
Duperthuy, Marylise
Wai, Sun Nyunt

Sub-Optimal Treatment of Bacterial Biofilms
Antibiotics, 5(2)

2016

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Mondal, Ayan
Tapader, Rima
Chatterjee, Nabendu Sekhar; et al.

Cytotoxic and Inflammatory Responses Induced by Outer Membrane Vesicle-Associated Biologically Active Proteases from Vibrio cholerae
Infection and Immunity, 84(5): 1478-1490

2016

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Karah, Nabil
Dwibedi, Chinmay Kumar
Sjöström, Karin; et al.

Novel Aminoglycoside Resistance Transposons and Transposon-Derived Circular Forms Detected in Carbapenem-Resistant Acinetobacter baumannii Clinical Isolates
Antimicrobial Agents and Chemotherapy, 60(3): 1801-1818

2016

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Edwin, Aaron
Persson, Cecilia
Mayzel, Maxim; et al.

Structure of the N-terminal domain of the metalloprotease PrtV from Vibrio cholerae
Protein Science, 24(12): 2076-2080

2015

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Kunsmann, Lisa
Rueter, Christian
Bauwens, Andreas; et al.

Virulence from vesicles: Novel mechanisms of host cell injury by Escherichia coli O104:H4 outbreak strain
Scientific Reports, 5

2015

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Department of Molecular Biology
Umeå University
901 87 Umeå 

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6K och 6L, Sjukhusområdet

Tel:  +46 (0)90-7856704

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