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  • Dual roles of capsular extracellular polymeric substances in photocatalytic inactivation of Escherichia coli: Comparison of E. coli BW25113 and isogenic mutants

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    Author(s)
    Huang, Guocheng
    Xia, Dehua
    An, Taicheng
    Ng, Tsz Wai
    Yip, Ho Yin
    Li, Guiying
    Zhao, Huijun
    Wong, Po Keung
    Griffith University Author(s)
    Zhao, Huijun
    Year published
    2015
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    Abstract
    The dual roles of capsular extracellular polymeric substances (EPS) in the photocatalytic inactivation of bacteria were demonstrated in a TiO2-UVA system, by comparing wild-type Escherichia coli strain BW25113 and isogenic mutants with upregulated and downregulated production of capsular EPS. In a partition system in which direct contact between bacterial cells and TiO2 particles was inhibited, an increase in the amount of EPS was associated with increased bacterial resistance to photocatalytic inactivation. In contrast, when bacterial cells were in direct contact with TiO2 particles, an increase in the amount of capsular ...
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    The dual roles of capsular extracellular polymeric substances (EPS) in the photocatalytic inactivation of bacteria were demonstrated in a TiO2-UVA system, by comparing wild-type Escherichia coli strain BW25113 and isogenic mutants with upregulated and downregulated production of capsular EPS. In a partition system in which direct contact between bacterial cells and TiO2 particles was inhibited, an increase in the amount of EPS was associated with increased bacterial resistance to photocatalytic inactivation. In contrast, when bacterial cells were in direct contact with TiO2 particles, an increase in the amount of capsular EPS decreased cell viability during photocatalytic treatment. Taken together, these results suggest that although capsular EPS can protect bacterial cells by consuming photogenerated reactive species, it also facilitates photocatalytic inactivation of bacteria by promoting the adhesion of TiO2 particles to the cell surface. Fluorescence microscopy and scanning electron microscopy analyses further confirmed that high capsular EPS density led to more TiO2 particles attaching to cells and forming bacterium-TiO2 aggregates. Calculations of interaction energy, represented by extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) potential, suggested that the presence of capsular EPS enhances the attachment of TiO2 particles to bacterial cells via acid-base interactions. Consideration of these mechanisms is critical for understanding bacterium-nanoparticle interactions and the photocatalytic inactivation of bacteria.
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    Journal Title
    Applied and Environmental Microbiology
    Volume
    81
    Issue
    15
    DOI
    https://doi.org/10.1128/AEM.00775-15
    Copyright Statement
    © 2015 American Society for Microbiology. The attached file is reproduced here in accordance with the copyright policy of the publisher. Please refer to the journal's website for access to the definitive, published version.
    Subject
    Microbiology not elsewhere classified
    Publication URI
    http://hdl.handle.net/10072/125021
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    • Journal articles

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