Biology Department Seminar

Molecular information theory provides a sensitive way to measure sequence conservation (in bits) at DNA-binding sites. Using information theory we built promoter models and SD models for T7-like phages. The results show that all T7 group phages have excess information in their promoters and SD sequences, while temperate phages have no excess, suggesting that the excess information may be used by the T7 group phages to efficiently take over their hosts. To explore whether bacterial genomes have phage promoters, the T7-like promoter models were scanned across more than 200 bacterial genomes. More than 100 promoters were found, and within these, 12 clusters of tandem promoters were located in a novel group of genetic islands in nine enteropathogens. We named these islands T7 islands, which may depend on T7-like phages for activation. These results raised a practical concern, that is, introducing a T7 RNAP-based expression system into a bacterial strain may cause serious unanticipated consequences.