The Thin Line Between Gut Commensal and Pathogen

Are gut microbes man9s best friend? They certainly seem to be, as the bacterial flora of the human gut benefit us by breaking down the complex carbohydrates in our food. However, sometimes certain bacterial strains acquire new traits, including antibiotic resistance and turn against us, resulting in serious infections. In their Perspective, Gilmore and Ferretti discuss the genome sequences of two important gut bacteria, a and a commensal turned bad and the secrets they hold about the lifestyles of these two important species ( Xu et al ., Paulsen et al .).