The intestinal retention and persistence of lactic acid
bacteria
(LAB) are strain-specific and affected by the bacterial surface components.
However, the contribution of surface adhesins of LAB to intestinal
adhesion and colonization remains unclear. In the present study, seven
gene knockout mutants (genes related to surface adhesin synthesis)
of Lacticaseibacillus paracasei
S-NB were derived based on the Cre-lox-based
recombination system. Results showed that the capsule layer appeared
thinner in the cell wall of S-NBΔ7576, S-NBΔdlt, and S-NBΔsrtA mutants when compared with the wild-type (WT) S-NB. The effects of S-NB_7576 (wzd and wze genes, responsible for capsular
polysaccharide synthesis) and S-NB_srtA (sortase A) mutation on the hydrophobicity, surface charge, and
adhesion ability seem to vary strongly among seven mutant strains.
In vivo colonization experiments showed a decrease in the colonization
numbers of S-NBΔ7576 and S-NBΔsrtA in both the ileal and colon lumen
from 2 to 8 days when compared with those of the WT S-NB. In conclusion, the synthesis of capsular polysaccharides and
the transport of surface proteins are closely related to the adhesion
ability and intestinal colonization of L. paracasei
S-NB.