Exploring the role of the auxiliary metabolic gene cpeT from the cyanophage Syn9 during infection

Infection of a bacterium by a phage transforms the host cell into a so-called virocell which shifts its normal cellular activities towards producing viral components. During phage infection, cyanobacteria undergo significant changes in host metabolic pathways such as photosynthesis, carbon-, and fatty acid- metabolism. These changes are supported by so called auxiliary metabolic genes (AMGs) encoded in the phage genome. Those host-like genes are thought to improve the host metabolism during the infection cycle. AMGs are frequently found in cyanophage genomes(1,2). We are investigating the role of a particular AMG, the gene cpeT encoding a putative phycobiliprotein lyase from the cyanophage Syn9. Lyases in the host are involved in the assembly of the light harvesting phycobilisome and similar functions are to be expected from the phage copy. A recombinant Syn9 phage lacking the cpeT gene was generated by homologous recombination in the infected host Synechococcus sp. WH8109. Recombinant phage particles were first enriched and subsequently purified. Recombinant phage lysates are assessed for their efficiency in infection, viral particle production and host phycobilisome assembly. Furthermore, complementation of the recombinant phages during infection, protein-protein interactions, and biochemical characterization of CpeT will be performed to demonstrate the specific role and effect of CpeT from Syn 9. All strategies aim to gain insight into the role of phage CpeT during infection and how it shapes the virocell metabolism.