Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0809533106 (2009)

A pathogen that can cause gum disease in humans uses signals from another species to bolster its defences, find Matthew Ramsey and Marvin Whiteley of the University of Texas in Austin.

They report that hydrogen peroxide secreted by Streptococcus bacteria stimulated Aggregatibacter actinomycetemcomitans to make more of a protein called ApiA, via a protein that acts as a sensor, OxyR. ApiA increases A. actinomycetemcomitans's binding to a human protein called factor H, shielding this bacterial species from attack by the human immune system.