Therefore, we isolated IL-1β expression-inhibitory Lactobacillus gasseri NK109 from the bacterial collection of human feces and examined the effects of NK109 and its lysates (membrane and cytosolic fractions) on Escherichia coli K1-induced gut microbiota alteration, colitis, depression, and cognitive impairment in germ-free and specific pathogen-free (SPF) mice. The gene discussed is IL1B; the disease is major depressive disorder.