The Other Isometric Phages

Abstract

ϕX174, S13, and G4 are only three members of what appears to be a large and diverse family of small, tail-less, icosahedral coliphages whose genomes consist of circular single-stranded DNA of approximately 5500 bases. Twenty-one such viruses have been reported and named in the literature, but only 14 of these have been characterized well enough to place them indisputably in this family, and these are listed in Table 1. This paper will attempt to review and correlate the scattered published data on all of the small, tail-less isometric phages other than ϕX, S13, and G4.

These small isometric coliphages are present abundantly in sewage, have been reported from most parts of the world, and are probably present wherever Escherichia coli is found. They are extremely diverse, and no two isolates appear to be the same. For example, when the G phages were isolated (Godson 1974), one batch of raw sewage yielded four different ϕX-like phages, none of which was identical with ϕX or S13.

Host Range and Temperature Range
Wild-type isometric phages fall into two main categories: those that infect E. coli C strains and those that infect E. coli K12 strains (Table 1). This is a function of the host cell wall, and viral DNA from phages specific for E. coli C can transfect E. coli K12 spheroplasts and vice versa. Most of the phages have their own specific receptor sites, and it is relatively easy to pick spontaneous mutants of E. coli that are resistant to a chosen...