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Host-factor Requirements and Some Properties of α3 and Related Phages

Akira Taketo, Ken-ichi Kodaira


More than 20 strains of circular single-stranded DNA phages (Microviridae) have been reported. Despite their morphological similarity, certain differences in their biological properties have been observed. On the basis of host range and antigenicity, Bradley (1970) classified circular single-stranded DNA phages into three groups: A, B, and C. Although considerable data are available for phages in groups B (e.g., ϕ X174 and S13) and C (e.g., St-1 and ϕK), little is known about the replication properties of group-A phages. Moreover, the relationships among the three groups and several other strains isolated recently (such as U3, G4, G13, and G14) remain to be elucidated. In this article the properties of α3, a representative of the group-A phages, are compared with those of other microvirid phages, including U3, G4, and G14.

Properties of α3
The host range of α3 is usually limited to Escherichia coli C and B strains (Bradley 1970). Like ϕX, α3 can infect E. coli 15T, CR63·1, C600·1, and W2252 S-14 (Taketo 1977a). In contrast to ϕX and ϕA, α3 plates well on E. coli C/5, C/15, and AX729, but not on C/62. On the other hand, G4 forms plaques on C/62 but not on C/5, whereas G13 and G14 cannot infect C/15 (Godson 1974). In Table 1 the plating efficiency of α3 on newly isolated lipopolysaccharide (LPS) mutants of E. coli C (Feige and Stirm 1976) and B (Prehm et al. 1975) strains is compared with the plating efficiencies of several microvirid phages. Phages α3, G13, and G14...

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