Xenogeneic regulation of the ClpCP protease of Bacillus subtilis by a phage-encoded adaptor-like protein

SPO1 phage infection of Bacillus subtilis results in a comprehensive remodelling of processes leading to conversion of the bacterial cell into a factory for phage progeny production. A cluster of 26 genes in the SPO1 genome, called the host takeover module, encodes for potentially cytotoxic proteins for the specific shut down of various host processes including transcription, DNA synthesis and cell division. However, the properties and bacterial targets of many genes of the SPO1 host takeover module remain elusive. Through a systematic analysis of gene products encoded by the SPO1 host takeover module we identified eight gene products which attenuated B. subtilis growth. Out of the eight gene products that attenuated bacterial growth, a 25 kDa protein, called Gp53, was shown to interact with the AAA+ chaperone protein ClpC of the ClpCP protease of B. subtilis . Results reveal that Gp53 functions like a phage encoded adaptor protein and thereby appears to alter the substrate specificity of the ClpCP protease to modulate the proteome of the infected cell to benefit efficient SPO1 phage progeny development. It seems that Gp53 represents a novel strategy used by phages to acquire their bacterial prey. Significance statement Viruses of bacteria (phages) represent the most abundant living entities on the planet, and many aspects of our fundamental knowledge of phage–bacteria relationships remain elusive. Many phages encode specialised small proteins, which modulate essential physiological processes in bacteria in order to convert the bacterial cell into a ‘factory’ for phage progeny production – ultimately leading to the demise of the bacterial cell. We describe the identification of several antibacterial proteins produced by a prototypical phage that infects Bacillus subtilis and describe how one such protein subverts the protein control system of its host to benefit phage progeny development. The results have broad implications for our understanding of phage–bacteria relationships and the therapeutic application of phages and their gene products.