Colony of <i>E. coli</i> Mutants (IMAGE) Cell Press Caption Macro-colony shown is a mixture of two <i>E. coli</i> mutants engineered to either produce or scavenge AI-2 in the mouse gut. These strains are expressing yellow or blue fluorescent proteins for easy visualization in fecal samples collected from mice colonized with these strains. Credit Ozhan Ozkaya Usage Restrictions Credit Required. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.