Gut complement induced by the microbiota combats pathogens and spares commensals.

Canonically, the complement system is known for its rapid response to remove microbes in the bloodstream. However, relatively little is known about a functioning complement system on intestinal mucosal surfaces. Herein, we report the local synthesis of complement component 3 (C3) in the gut, primarily by stromal cells.

Microbiome induced complement synthesized in the gut protects against enteric infections.

Unlabelled: Canonically, complement is a serum-based host defense system that protects against systemic microbial invasion. Little is known about the production and function of complement components on mucosal surfaces. Here we show gut complement component 3 (C3), central to complement function, is regulated by the composition of the microbiota in healthy humans and mice, leading to host-specific gut C3 levels.

Separating Functions of the Phage-Encoded Quorum-Sensing-Activated Antirepressor Qtip.

Quorum sensing is a process of chemical communication that bacteria use to track cell density and coordinate gene expression across a population. Bacteria-infecting viruses, called phages, can encode quorum-sensing components that enable them to integrate host cell density information into the lysis-lysogeny decision. Vibriophage VP882 is one such phage, and activation of its quorum-sensing pathway leads to the production of an antirepressor called Qtip.