Interbacterial Chemical Communication-Triggered Nascent Proteomics

Metabolic labeling with clickable noncanonical amino acids has enabled nascent proteome profiling, which can be performed in a cell-type-specific manner. However, nascent proteomics in an intercellular communication-dependent manner remains challenging. Here we develop communication-activated profiling of protein expression (CAPPEX), which integrates the LuxI/LuxR quorum sensing circuit with the cell-type-specific nascent proteomics method to enable selective click-labeling of newly synthesized proteins in a specific bacterium upon receiving chemical signals from another reporter bacterium. CAPPEX reveals that E. coli competes with Salmonella for tryptophan as the precursor for indole, and the resulting indole suppressed the expression of virulence factors in Salmonella. This tryptophan-indole axis confers attenuation of Salmonella invasion in host cells and living mice. The CAPPEX strategy should be widely applicable for investigating various interbacterial communication processes.

Role of the intestinal microbiota in resistance to colonization by Clostridium difficile

Antibiotic-associated infection with the bacterial pathogen Clostridium difficile is a major cause of morbidity and increased health care costs. C difficile infection follows disruption of the indigenous gut microbiota by antibiotics. Antibiotics create an environment within the intestine that promotes C difficile spore germination, vegetative growth, and toxin production, leading to epithelial damage and colitis. Studies of patients with C difficile infection and animal models have shown that the indigenous microbiota can inhibit expansion and persistence of C difficile. Although the specific mechanisms of these processes are not known, they are likely to interfere with key aspects of the pathogen's physiology, including spore germination and competitive growth. Increasing our understanding of how the intestinal microbiota manage C difficile could lead to better means of controlling this important nosocomial pathogen.