The cycle for a Siphoviridae-like phage (VHS1) of Vibrio harveyi is dependent on the physiological state of the host

In a previous report, we isolated Vibrio harveyi (VH) 1114 together with its bacteriophage, VHS1, from a black tiger shrimp-rearing pond. The VHS1 has its lysogenic relationship to the VH1114 host as either true lysogen (TL) or pseudolysogen (PL). The characters of TL are based on the extrachromosomal existence of the VHS1 phage genome in the VH host which also simultaneously produces the VHS1 phage particles and is resistant to super-infection. The original VH1114 host exhibits a clear plaque after infection with VHS1 phage. The PL, on the other hand, exhibits a turbid plaque and does not possess the phage genome but shows toleration to the phage infection. Maintaining the PL in artificial seawater (ASW) for 1 h causes the PL to be sensitive to VHS1 infection and results in clear plaques as in the original clone. A chloramphenical-added-ASW treated pseudolysogen clone (PLC), however, prevented VHS1 infection. It is postulated that the infection of VHS1 phage is regulated with a phage binding receptor which supposed to be inducible.