Table 3.

Fitness of promoter mutants is greater than ancestor at 42°C*.

Temperature	Host	F-test	Pr > F	t-value	Pr > |t|
37°	Escherichia coli	41.4	<0.0001	6.7	<0.0001
37°	Salmonella typhimurium	10.6	0.0013	-4.6	0.0010
37°	Shigella sonnei	70.6	<0.0001	11.3	<0.0001
42°	Escherichia coli	35.4	<0.0001	-8.6	<0.0001
42°	Salmonella typhimurium	14.8	0.0003	-6.6	<0.0001
42°	Shigella sonnei	53.2	<0.0001	-13.9	<0.0001

*ANOVA on doublings per hour for each environmental condition with 4 degrees of freedom for each test, and t-test comparing ancestor to all mutants.