1993), but its function in phages is unclear (Goldsmith et al.2011). Other genes related to P metabolism within cyanophages have also been identified: pstS encoding a potential periplasmic phosphate binding protein and phoA encoding a putative alkaline phosphatase (Sullivan et al.2010). Intriguingly, only pstS is overexpressed during infection of a P-deplete host (Lin, Ding and Zeng 2016). This evidence concerns the gene KLK4 and infection.