"In this electron micrograph of a single X. nematophilus cell, the black region is the bacterium and the gray filaments are the flagella that the bacteria use to propel themselves. These bacteria are capable of switching their lifestyle. In one host they are pathogens and in the other host they are mutualistic symbionts. Identifying the factors that allow the bacteria to recognize the host environment and regulate the gene expression accordingly represents an exciting avenue of research."