FIG 5.

The CTD mutation resulted in decreased viability of topA66 mutant DPB636 following stress challenge. DPB635 (topA⁺) and DPB636 (topA66) were treated with 100 to 250 ng/ml of norfloxacin for 17 h (A), 250 ng/ml of norfloxacin for the indicated time periods (B), 0.4, 0.8, or 1 mM N-ethylmaleimide (NEM) for 1 h (C), or 0.4 mM NEM for the indicated time periods (D). Viable colony counts were determined before and after treatment by serial dilutions and plating on LB plates. The relative survival ratio after different treatments is calculated by dividing the viable colonies at the indicated time period or concentration by the viable count of respective nontreated cultures. Error bars correspond to standard deviations.