FIG. 1.

Viability analysis of M. leprae and real-time RT-PCR analysis of M. leprae genes using RNA from nude mouse-derived M. leprae held in prewarmed medium at 33°C or 37°C for 4 h or 42°C for 2 h. (a) Percent relative viability values were obtained from 7-day Buddemeyer radiorespirometry readings (counts per minute) from M. leprae held at 37°C or at 45°C divided by that of M. leprae held at 33°C for each time period and each temperature. Values represent the mean and standard deviation of at least six observations for each time. A single asterisk denotes that the percent relative viability values between the 2-h 37°C incubation and other indicated times are considered significantly different at P < 0.001; a double asterisk denotes that the percent relative viability values between the 2-h 37°C incubation and other indicated times are considered significantly different at P < 0.05. (b and c) The increases of mRNA levels for sigma factor gene transcripts (b) and heat shock gene transcripts (c) due to heat stress were obtained by normalizing each template for potential template concentration differences by dividing each of the mRNA values by that of the 16S rRNA value from a 1:10⁻⁵ dilution of the same cDNA template and dividing these values by those of those of M. leprae held at 33°C.