Figure. 1. Examples of contact-dependent alteration in metabolism and growth.
(A). Escherichia coli containing the cdiBAI genes express CdiB, which is predicted to reside in the outer membrane and function in export of CdiA to the cell surface. CdiA is postulated to mediate binding to the BamA receptor in the outer membrane (OM) of target cells, and reduce the proton gradient, respiration, ATP, and cell growth/division of target cells. CdiI provides immunity to autoinhibition by cognate CdiA effector. The CDI mechanism may involve interaction with the multidrug efflux pump AcrB located in the inner membrane (IM) [6,7,9] .
(B). Pelotomaculum thermopropionicum strain S1 expresses flagella that bind to its syntrophic partner Methanothermobacter thermoautotrophicus strain △H, keeping the cells close by tethering. Binding of the FliD cap protein of the flagellum to an unidentified receptor on M. thermoautotrophicus alters cellular metabolism including induction of methane formation. Hydrogen gas from P. thermopropionicum is used for methane production, and serving to keep H2 levels low and enabling continued fermentation of propionate by P. thermopropionicum •[12].