Work on the few well-studied phages, i. e., l, T4 and T7, served a rich source of regulatory paradigms throughout the last 30 years. It is estimated that the variety of phages exceeds the variety of living bacteria by an order of magnitude or more. Thus, there exist a vast, virtually untapped source of inhibitory mechanisms that needs to be studied. The Eliava group is the source of one of the most extensive phage collections in the world and has been successfully using virulent bacteriophages as therapeutics. The US collaborator has an established program studying the molecular mechanisms of regulation of bacterial host transcription regulation during bacteriophage infection. Our objective is to combine the complementary expertise of the two groups to obtain deeper insights into phage evolution and the mechanisms of negative transcription regulation employed by diverse bacteriophages during host shut-off. The increased molecular understanding of therapeutic phages is expected to open the way for construction of more potent antibacterial agents. Our specific aims are as follows:

1. We will perform limited and, when warranted, complete genomic sequencing of a select group of Eliava collection bacteriophages that infect pathogenic bacteria.

2. We will perform a systematic survey of bacteriophages present in the Eliava collection to identify phages that orchestrate host transcription shut-off early in their development. We will then use the modern biochemical methods and discriminative in vitro transcription assays to uncover the underlying mechanisms and RNA polymerase targets.