φγ: A Coliphage Related to, but Distinct from the φ80 Virion

The coliphage phi gamma, though capable of genetic recombination with phi 80, is morphologically distinct from the phi 80 virion. It has a prolate head (58.4 X 46.7 nm) bearing a tail (143 nm) which is strikingly flexible. On the basis of their buoyant density in CsC1, both infectious and transducing phi gamma particles form a single population. This density value is slightly higher than that of the phi 80 virion. The phi gamma chromosome is a double-stranded linear DNA molecule of 13.4 mum in length (corresponding mol. wt.: 27.6 X 10(6)). From its melting temperature and its buoyant density in CsC1, phi gamma DNA appears to have a base composition very close to that of Escherichia coli DNA.