Peptidoglycan analysis reveals that synergistic deacetylase activity in vegetative impacts the host response.

is an anaerobic and spore-forming bacterium responsible for 15-25% of postantibiotic diarrhea and 95% of pseudomembranous colitis. Peptidoglycan is a crucial element of the bacterial cell wall that is exposed to the host, making it an important target for the innate immune system. The peptidoglycan is largely -deacetylated on its glucosamine (93% of muropeptides) through the activity of enzymes known as -deacetylases, and this -deacetylation modulates host-pathogen interactions, such as resistance to the bacteriolytic activity of lysozyme, virulence, and host innate immune responses. genome analysis showed that 12 genes potentially encode -deacetylases; however, which of these -deacetylases are involved in peptidoglycan deacetylation remains unknown. Here, we report the enzymes responsible for peptidoglycan -deacetylation and their respective regulation. Through peptidoglycan analysis of several mutants, we found that the deacetylases PdaV and PgdA act in synergy. Together they are responsible for the high level of peptidoglycan -deacetylation in and the consequent resistance to lysozyme. We also characterized a third enzyme, PgdB, as a glucosamine -deacetylase. However, its impact on -deacetylation and lysozyme resistance is limited, and its physiological role remains to be dissected. Finally, given the influence of peptidoglycan -deacetylation on host defense against pathogens, we investigated the virulence and colonization ability of the mutants. Unlike what has been shown in other pathogenic bacteria, a lack of -deacetylation in is not linked to a decrease in virulence.