KRT1 and major depressive disorder: Therefore, we isolated inflammatory E. coli K1 and anti-inflammatory Lactobacillus mucosae (formerly Lactobacillus reuteri) NK41 from healthy human gut microbiota and examined whether K1 could cause altered microbiota, colitis, cognitive decline, and depression in mice and whether NK41 reduced K1-induced altered microbiota, cognitive decline, and depression in mice.