The Replication Cycle of ΦKZ depends on a Phage-encoded Nuclease

Bacteriophages with genomes larger than 200 kBp, known as jumbo phages, interact with their hosts in complex ways. The P. aeruginosa phage ΦKZ, for example, encodes more than 300 genes, most of which are of unknown function. Using a novel mRNA-based knockdown approach, we screened for essential genes, leading to the identification of ΦKZ155. Knockdown of this gene abrogated phage replication and further analysis revealed that ΦKZ155 encodes an RNase HI, which is crucial for the replication of the phage genome.