The Good and the Bad (image) Washington University School of Medicine Caption Differences in the way they use their genes cause different strains of the E. coli bacterium to take on different hues. The beaker in the foreground contains strains of bacteria linked to urinary tract infections, while the background beaker holds more benign strains of bacteria isolated from the gut. Scientists are hoping to develop drugs that specifically target infection-causing strains of bacteria like those in the foreground beaker. Credit Michael Purdy/Washington University School of Medicine in St. Louis Usage Restrictions None 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.