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.
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.