WalK(S221P) Mutation Promotes the Production of Capsules Through an MgrA-Dependent Pathway.

is a vital pathogen causing clinical infections. Capsules are important virulence factors for . . This study investigates the regulatory mechanisms underlying capsule production in . Bacterial strains XN108 and Newman were used, and combined approaches like RNA sequencing (RNA-seq), RT-qPCR, transmission electron microscopy (TEM), gene reporter, and electrophoretic mobility shift assay (EMSA) were performed to test the role and mechanism of WalK(S221P) mutation in capsule production. RNA-seq showed an increased expression of genes in the WalK(S221P)-carried XN108 relative to the mutation-cured XN108-R. TEM and capsular polysaccharide determination demonstrated that XN108 produced more capsules than XN108-R did. Similar results were presented in the WalK(S221P)-contained K-Newman versus the wild-type Newman. RT-qPCR screening showed an increasing expression of the gene in XN108 versus XN108-R. Gene reporter and EMSA analysis revealed that WalK(S221P) mutation promoted capsule production through MgrA. Deletion of decreased the WalK(S221P)-mediated capsule yield. Moreover, WalK(S221P) mutation remarkably increased the tolerance of to whole blood killing and microphage phagocytosis. Overall, these data provide mechanistic insights into the effect of WalK(S221P) on the capsule production of , which may set down foundations for future virulence investigations.