FIG 1.

Expression of the SPI-1 gene sipC is repressed following growth at 42°C. (A) The body temperatures of a W-36 line of chickens were measured 1, 2, 4, 6, 8, 13, and 22 days posthatch (indicated by dashed lines). By day 8, the body temperature was not significantly different than at day 6 (P < 0.05 [Student's t test and Bonferroni adjustment for multiple comparisons]). (B) A sipC-lacZ fusion strain (RM5385) was used to test the impact of different temperatures on the regulation of SPI-1. Bacteria were grown overnight in LB medium under standing conditions at 37°C and diluted 50-fold in LB medium containing MOPS (pH 7.4, 100 mM) and glucose (1 mM) and incubated at different temperatures under standing conditions for approximately 16 to 18 h. β-Galactosidase activity was determined from experiments performed on three separate occasions. Data shown are the means ± SD, with reporter activity under the 37°C conditions set to 100%.