Nature
Volume 467 Number 7311 pp7-124  2 September 2010
http://www.nature.com/nature/current_issue.html

Letters
Bacterial charity work leads to population-wide resistance

Summary
Bacteria regularly evolve antibiotic resistance, but little is known about this process at the population level. Here, a continuous culture of Escherichia coli facing increasing antibiotic levels is followed. Most isolates taken from this population are less antibiotic resistant than the population as a whole. A few highly resistant mutants provide protection to the less resistant constituents, in part by producing the signalling molecule indole, which serves to turn on drug efflux pumps and oxidative-stress protective mechanisms.

Henry H. Lee, Michael N. Molla, Charles R. Cantor & James J. Collins