Construction of Attenuated Listeria monocytogenes Strain EGDe-sigB and Preliminary Identification of Biological Activity of sigB
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Abstract:
Listeria monocytogenes is a foodborne pathogen infectious to both humans and animals. L. monocytogenes can cross the human intestinal barrier, placental barrier, and blood-brain barrier, thereby causing gastroenteritis, meningitis, miscarriage, and other diseases. Sigma B factor, encoded by the gene sigB, is an important regulatory factor for the environmental stress response in many Gram-positive bacteria, and directly and indirectly controls the expression of important virulence genes, such as prfA and inlA. The sigB gene of L. monocytogenes strain EGDe was knocked out by homologous recombination, and the resulting deletion strain (EGDe-ΔsigB) was used to study the effect of sigB deletion on growth, expression of 13 virulence genes (including inlA, inlB, and prfA), and invasion of Caco-2 intestinal epithelial cells. The results showed that the growth rate of the EGDe-ΔsigB strain was equivalent to that of the wild-type EGDe strain. Deletion of sigB caused a significant reduction in the expression levels of inlA and inlB, but a significant (four- to five-fold) increase in the expression levels of the virulence genes actA and plcA, demonstrating that sigB has a relatively large influence on the expression of some virulence genes in L. monocytogenes. Furthermore, invasion assays indicated that deletion of sigB caused a decline in the ability of L. monocytogenes strain EDGe to invade Caco-2 cells.
