Table 3.

The CARD9 gene mutation and its impact on the microbiota in IBD.

	Genes Studied	Conclusions of the Study
Aminal studies	CARD9 gene	Disturbed microbial tryptophan metabolism in CARD9 was associated with susceptibility to colitis. Administration of Lactobacillus strains that metabolize tryptophan to AHR ligands was sufficient to reduce colitis in CARD9 -/- mice. The gut microbiota of CARD9-/- mice has a pro-inflammatory effect because it enhances colitis when transferred to germ-free wild-type mice [61]. CARD9 effectively controlled staphylococcal virulence to promote pathogen elimination through gut microbiota-independent and -dependent mechanisms. Mice with induced colitis had lower levels of Clostridiaceae and higher levels of Firmicutes in the basal composition of fecal bacteria. The fecal fungal composition of CARD9-/- mice was altered and dominated by representatives of the Ascomycota, Basidiomycota, and Zygomycota types. Genetic susceptibility to intestinal pathogens can be counteracted by dietary intervention, which restores humoral immunity and a competitive microbiota [64].