Growth of Bacteriophage φX-174 at Elevated Temperatures

The replication of bacteriophage φX-174 is impaired at temperatures above 40 °C. Mutants (ht) that replicate at high temperature were isolated and partially characterized. Wild-type φX fails to grow at high temperature because, unlike the mutants, it does not make appreciable amounts of single-stranded (ss)DNA. An unusual form of ssDNA, not found in complete virions, is described.