Characterization of Φ8, a bacteriophage containing three double-stranded RNA genomic segments and distantly related to Φ6

The three double-stranded RNA genomic segments of bacteriophage Phi 8 were copied as cDNA, and their nucleotide sequences were determined. Although the organization of the genome is similar to that of Phi 6, there is no similarity in either the nucleotide sequences or the amino acid sequences, with the exception of the motifs characteristic of Viral RNA polymerases that are found in the presumptive polymerase sequence. Several features of the viral proteins differ markedly from those of Phi 6. Although both phages are covered by a lipid-containing membrane, the protein compositions are very different. The most striking difference is that protein P8, which constitutes a shell around the procapsid in Phi 6, is part of the membrane in Phi 8. The host attachment protein consists of two peptides rather than one and the phage attaches directly to the lipopolysaccharide of the host rather than to a type IV pilus. The host range of Phi 8 includes rough strains of Salmonella typhimurium and of pseudomonads (C) 2000 academic Press.