The above is a diagrammatic representation of host-takeover. Top: Uninfected cell, replicating and transcribing its DNA. Middle: Newly infected cell, expressing the host-takeover genes of SPO1. Bottom: Later in infection, host genome has been shut down, while phage genome is actively replicated and expressed.
We are analyzing the mechanisms by which SPO1 accomplishes this takeover of the host cell. We have identified a cluster of 24 genes in the terminal redundancy of SPO1, which specifies most or all of the necessary machinery. By observing the effect of expression of each gene in uninfected cells, and the effect of mutational inactivation of each gene on the progress of infection, we are defining the specific roles of the 24 gene products. Activities that have been identified for specific gene products include: (1) shutoff of host DNA and RNA synthesis; (2) regulation of the timing of those shutoffs; (3) inhibition of host cell division; and (4) regulation of expression of the 24 genes.
The broad spectrum bactericidal activity of some of these gene products makes them a potential basis for development of new antibiotics.