PROCESS OF INFECTION WITH BACTERIOPHAGE PHIX174 .25. STUDIES WITH BACTERIOPHAGE PHIX174 MUTANTS BLOCKED IN PROGENY REPLICATIVE FORM DNA SYNTHESIS

φX174 amber mutants in cistron VI synthesize only the parental replicative form under non-permissive conditions. The specific infectivity (infectivity per molecule) of this RF‡ ‡ Abbreviations used: RF, replicative form; CM, chloramphenicol; dodecyl SO4, sodium dodecyl sulfate; TCA, trichloroacetic acid. is similar to the parental RF made under permissive conditions. After infection of non-permissive cells with a cistron VI mutant, the parental RF attaches to a rapidly sedimenting component (membrane). The majority of this bound RF sediments as RFII. These results are similar to those obtained with wild type infection (Knippers & Sinsheimer, 1968) or with a cistron VI mutant under permissive conditions. φX lyticless mutants that synthesize normal quantities of progeny RF DNA in 0 or 30 μg of chloramphenicol/ml. do not produce progeny RF molecules when 150 μg of CM/ml. is added before infection. Addition of 150 μg of CM/ml. at eight minutes after infection (before single strand synthesis has begun) stops the production of cistron VI protein but allows RF replication to continue at onehalf the rate observed in 30 μg of CM/ml. Experiments with a cistron VI temperature-sensitive mutant demonstrate that the cistron VI gene product is continuously required for the synthesis of al progeny RF molecules. This protein does not appear to be needed for single stran synthesis. © 1969.