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A mucin-responsive hybrid two-component system controls Bacteroides thetaiotaomicron colonization and gut homeostasis
Ju-Hyung Lee , Soo-Jeong Kwon , Ji-Yoon Han , Sang-Hyun Cho , Yong-Joon Cho , Joo-Hong Park
J. Microbiol. 2022;60(2):215-223.   Published online February 1, 2022
DOI: https://doi.org/10.1007/s12275-022-1649-3
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AbstractAbstract
The mammalian intestinal tract contains trillions of bacteria. However, the genetic factors that allow gut symbiotic bacteria to occupy intestinal niches remain poorly understood. Here, we identified genetic determinants required for Bacteroides thetaiotaomicron colonization in the gut using transposon sequencing analysis. Transposon insertion in BT2391, which encodes a hybrid two-component system, increased the competitive fitness of B. thetaiotaomicron. The BT2391 mutant showed a growth advantage in a mucin-dependent manner and had an increased ability to adhere to mucus-producing cell lines. The increased competitive advantage of the BT2391 mutant was dependent on the BT2392–2395 locus containing susCD homologs. Deletion of BT2391 led to changes in the expression levels of B. thetaiotaomicron genes during gut colonization. However, colonization of the BT2391 mutant promoted DSS colitis in low-fiber diet-fed mice. These results indicate that BT2391 contributes to a sustainable symbiotic relationship by maintaining a balance between mucosal colonization and gut homeostasis.
Characterization of a novel phage depolymerase specific to Escherichia coli O157:H7 and biofilm control on abiotic surfaces
Do-Won Park , Jong-Hyun Park
J. Microbiol. 2021;59(11):1002-1009.   Published online October 6, 2021
DOI: https://doi.org/10.1007/s12275-021-1413-0
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AbstractAbstract
The increasing prevalence of foodborne diseases caused by Escherichia coli O157:H7 as well as its ability to form biofilms poses major threats to public health worldwide. With increasing concerns about the limitations of current disinfectant treatments, phage-derived depolymerases may be used as promising biocontrol agents. Therefore, in this study, the characterization, purification, and application of a novel phage depolymerase, Dpo10, specifically targeting the lipopolysaccharides of E. coli O157, was performed. Dpo10, with a molecular mass of 98 kDa, was predicted to possess pectate lyase activity via genome analysis and considered to act as a receptor- binding protein of the phage. We confirmed that the purified Dpo10 showed O-polysaccharide degrading activity only for the E. coli O157 strains by observing its opaque halo. Dpo10 maintained stable enzymatic activities across a wide range of temperature conditions under 55°C and mild basic pH. Notably, Dpo10 did not inhibit bacterial growth but significantly increased the complement-mediated serum lysis of E. coli O157 by degrading its O-polysaccharides. Moreover, Dpo10 inhibited the biofilm formation against E. coli O157 on abiotic polystyrene by 8-fold and stainless steel by 2.56 log CFU/coupon. This inhibition was visually confirmed via fieldemission scanning electron microscopy. Therefore, the novel depolymerase from E. coli siphophage exhibits specific binding and lytic activities on the lipopolysaccharide of E. coli O157 and may be used as a promising anti-biofilm agent against the E. coli O157:H7 strain.

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