FIG 1.

The TLD phenomenon and its modifiers, a general explanation, and the effect of CRC doubling. (A) The three phases of TLD kinetics in the thyA mutant (at 37°C): (i) the resistance phase (no loss of CFU titer), (ii) the rapid exponential death (RED) phase (CFU titer loss of 3 orders of magnitude), and (iii) the survival phase (stabilization of the CFU titer). At time zero, the dT supplementation was removed (and chloramphenicol was added in the +Cam culture). The strains are as follows: thyA mutant, KKW58; thyA recBCD mutant, KJK63. The kinetics of the thyA recBCD double mutant, as well as the thyA mutant without dT but in the presence of chloramphenicol, are shown as examples of modified behavior during T starvation. Here and in all figures, unless indicated otherwise, all values are means of the results of 3 to 12 independent measurements ± standard error of the mean (SEM). (B) A possible scheme of the futile fork breakage-repair cycle. (C) ori/ter ratios in the rep and seqA mutants grown in the presence of dT. The strains are as follows: thyA mutant, KKW58; thyA rep mutant, KJK202; thyA seqA mutant, SRK271. (D) Schemes of the replicating chromosomes in WT cells (top) versus rep or seqA mutants (bottom). (E) TLD kinetics of the thyA rep and thyA seqA double mutants compared with the thyA single mutant. The strains are as described for panel C.