Delta phage (IMAGE) University of Maryland Baltimore County Caption A delta bacteriophage, the first identified in a new study in Frontiers in Microbiology to have binding sites for CtrA, a protein produced by the bacteriophage's host that regulates the production of pili and flagella. The presence of these binding sites only in phages that require their host cells to have pili/flagella in order to infect them suggests that the phage is monitoring the presence of this protein in order to "decide" whether to stay put or replicate and emerge from its host cell. Credit Tagide deCarvalho/UMBC Usage Restrictions attribution and explicit permission required. Exceptions: EurekAlert has permission to use this image, and any publication that republishes the release in full may also accompany it with this image, as long as that publication includes attribution. License Original 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.