HF1 and HF2: novel bacteriophages of halophilic archaea

Two novel halophilic archaebacterial bacteriophages, HF1 and HF2, were isolated from an Australian solar saltern. They were morphologically identical with icosahedral-shaped heads (diameter 58 nm) and contractile tails (length 94 nm). Other similarities included sensitivity to reduced ionic conditions, similar protein profiles by SDS-PAGE, and dsDNA genomes of identical size (73.5 kbp) with analogous restriction patterns. DNA-DNA hybridization data showed the two phages to be closely related. HF1 has a broad host-range, infecting members of three halobacterial genera including Halobacterium salinarium and the genetically well-characterized strain Haloferax volcanii WFD11. Mutants showing increased plating efficiency on alternative hosts were readily selectable. By contrast, HF2 showed a limited host range, confined to the closely related dam-methylated strains Ch2 and H. saccharovorum.