Bacteria in the gut can protect themselves from the immune responses designed to wipe out infection. They achieve this by modifying their outer membranes to be resistant to antimicrobial peptides which hosts release to kill pathogens.
Andrew Goodman of Yale University in New Haven, Connecticut, and his team studied 17 bacterial species that are normally found in the gut. The resilience in bacterium Bacteroides thetaiotaomicron was linked to the expression a protein called LpxF. This protein prevents the positively charged peptides from binding to the gut microbe’s surface by neutralising the negative charge of the cell membrane. In mouse guts during inflammation, mutants that did not express LpxF were out competed by other microbes in the gut.