Edited by Chris WhitfieldSpores are produced by many organisms as a survival mechanism activated in response to several environmental stresses. Bacterial spores are multilayered structures, one of which is a peptidoglycan layer called the cortex, containing muramic-␦lactams that are synthesized by at least two bacterial enzymes, the muramoyl-L-alanine amidase CwlD and the N-deacetylase PdaA. This study focused on the spore cortex of Clostridium difficile, a Gram-positive, toxin-producing anaerobic bacterial pathogen that can colonize the human intestinal tract and is a leading cause of antibiotic-associated diarrhea. Using ultra-HPLC coupled with high-resolution MS, here we found that the spore cortex of the C. difficile 630⌬erm strain differs from that of Bacillus subtilis. Among these differences, the muramic-␦lactams represented only 24% in C. difficile, compared with 50% in B. subtilis. CD630_14300 and CD630_27190 were identified as genes encoding the C. difficile N-deacetylases PdaA1 and PdaA2, required for muramic-␦-lactam synthesis. In a pdaA1 mutant, only 0.4% of all muropeptides carried a muramic-␦lactam modification, and muramic-␦-lactams were absent in the cortex of a pdaA1-pdaA2 double mutant. Of note, the pdaA1 mutant exhibited decreased sporulation, altered germination, decreased heat resistance, and delayed virulence in a hamster infection model. These results suggest a much greater role for muramic-␦-lactams in C. difficile than in other bacteria, including B. subtilis. In summary, the spore cortex of C. difficile contains lower levels of muramic-␦-lactams than that of B. subtilis, and PdaA1 is the major N-deacetylase for muramic-␦-lactam biosynthesis in C. difficile, contributing to sporulation, heat resistance, and virulence.Clostridium difficile is a Gram-positive, spore-forming, toxin-producing anaerobic bacterium that can colonize the intes-
Mycobacterium tuberculosis ( M. tuberculosis ) causes an enormous burden of disease worldwide. As a central aspect of its pathogenesis, M. tuberculosis grows in macrophages, and host and microbe influence each other’s metabolism. To define the metabolic impact of M. tuberculosis infection, we performed global metabolic profiling of M. tuberculosis –infected macrophages. M. tuberculosis induced metabolic hallmarks of inflammatory macrophages and a prominent signature of cholesterol metabolism. We found that infected macrophages accumulate cholestenone, a mycobacterial-derived, oxidized derivative of cholesterol. We demonstrated that the accumulation of cholestenone in infected macrophages depended on the M. tuberculosis enzyme 3 β -hydroxysteroid dehydrogenase (3 β -Hsd) and correlated with pathogen burden. Because cholestenone is not a substantial human metabolite, we hypothesized it might be diagnostic of M. tuberculosis infection in clinical samples. Indeed, in 2 geographically distinct cohorts, sputum cholestenone levels distinguished subjects with tuberculosis (TB) from TB-negative controls who presented with TB-like symptoms. We also found country-specific detection of cholestenone in plasma samples from M. tuberculosis –infected subjects. While cholestenone was previously thought to be an intermediate required for cholesterol degradation by M. tuberculosis , we found that M. tuberculosis can utilize cholesterol for growth without making cholestenone. Thus, the accumulation of cholestenone in clinical samples suggests it has an alternative role in pathogenesis and could be a clinically useful biomarker of TB infection.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.