Interaction of the PhiHSIC virus with its host: lysogeny or pseudolysogeny?
The marine phage PhiHSIC has been previously reported to enter into a lysogenic relationship with its host, HSIC, identified as Listonella pelagia. This phage produces a variety of plaques on its host, including turbid and haloed plaques, from which lysogens were previously isolated. These lysogens were unstable during long-term storage at -80( degrees ) C and were lost. When HSIC was reinfected with phage PhiHSIC, pseudolysogen-like interactions between the phage and its host were observed. The cells (termed HSIC-2 or HSIC-2e) produced high viral titers (10(11) ml(-1)) in the absence of inoculating phage and yet reached culture densities of nearly 10(9) ml(-1). Prophages were not induced by mitomycin C or the polyaromatic hydrocarbon naphthalene in cells harboring such infections. However, such cells were homoimmune to superinfection. Colonies hybridized strongly with a gene probe from a 100-bp fragment of the PhiHSIC genome, while the host did not. Analysis of chromosomal DNA preparations suggested the presence of a chromosomally integrated prophage. Phage adsorption experiments suggested that HSIC-2 was adsorption impaired. Because of the chromosomal prophage integration and homoimmunity, we interpret these results to indicate that PhiHSIC establishes a lysogenic relationship with its host that involves an extremely high level of spontaneous induction. This could be caused by a weak repressor of phage production. Additionally, poor phage adsorption of HSIC-2 compared to the wild type probably helped maintain this pseudolysogen-like relationship. In many ways, pseudolysogenic phage-host interactions may provide a paradigm for phage-host interactions in the marine environment.
Williamson
S J
SJ
College of Marine Science, University of South Florida, 140 7th Avenue S., St. Petersburg, FL 33701, USA.
McLaughlin
M R
MR
Paul
J H
JH
D015139:Blotting, Southern; D020563:Gammaproteobacteria / Q000254:growth & development / Q000821:virology*; D008242:Lysogeny; D016685:Mitomycin / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D012623:Seawater / Q000382:microbiology / Q000821:virology; D017906:Siphoviridae / Q000235:genetics / Q000502:physiology*; D014775:Virus Activation / Q000187:drug effects
D009281:Naphthalenes; C031721:naphthalene; D016685:Mitomycin