ΦHSIC and its host, Listonella pelagia, were isolated from the waters near Oahu in 1995 (Jiang et al., 1998). ΦHSIC is a Siphoviridae that enters into a pseudolysogenic-like relationship with its host, resulting in sigmoidal growth curves and production of high numbers of host and phage in culture simultaneously. The pseudolysogen possesses a unique colony morphology, is resistant to superinfection, is not Mitomycin C inducible, and shows evidence of chromosomal integration (Williamson et al., 2001).
The ΦHSIC genome was sequenced using a combination of linker-amplified library construction (http://www.sci.sdsu.edu/PHAGE/LASL/, Lucigen Corp) followed by sequencing and primer walking. The genome (37966 bp; G+C = 44%) contained 47 putative ORFs, 17 of which had significant BLASTP hits in GenBank, including a β-subunit of DNA polymerase III, a helicase, a helicase-like subunit of a resolvasome complex, a terminase, a tail-tape measure protein, several phage-like structural proteins, and one ORF that may assist in host pathogenicity (an ADP ribosyltransferase; colors in figure correspond to BLASTP scores).
The genome was circularly permuted with no physical ends detected by sequencing or restriction enzyme digestion analysis, and lacked a cos-site. This evidence is consistent with a headful packaging mechanism similar to that of Salmonella phage P22 and Shigella phage Sf6. Because none of the phage-like ORFs were closely related to any existing phage sequences in GenBank (ie., none greater than 62% identical, and most < 25% identical at the amino acid level), ΦHSIC is unique amongst phages that have been sequenced to date. These results further emphasize the need to sequence phages from the marine environment, perhaps the largest reservoir of untapped genetic information.
Accession number: AY772740
Jiang, S.C., C.A. Kellogg, and J.H. Paul. 1998. Characterization of marine temperate phage-host systems isolated from Mamala Bay, Oahu, Hawaii. Appl. Environ. Microbiol. 64: 535-542.
Paul, J.H., S.J. Williamson, A. Long, R.N. Authement, D. John, A. M. Segall, F.L. Rohwer, M. Androlewicz, and S. Patterson. 2005. The complete genome of ΦHSIC, a pseudotemperate marine phage of Listonella pelagia. Appl. Environ. Microbiol. 71:3311-3320
Williamson, S., MR. McLaughlin, and J.H. Paul. 2001. Interaction of the Phage HSIC with its host. Lysogeny or Pseudolysogeny? Appl. Environ. Microbiol. 67:1682-1688.