Table 3. Evaluation of selective pressure during the MA experiments: position of BPS.

		BPSs in coding/noncoding DNA
Strain	Observed	Expected from genomea	χ2a	P	Expected from simulationsb	χ2b	P
MA experiments on LB
mutD5	5.47	5.74	2.0	0.15	5.51	0.05	0.83
mutD5 mutL	6.96	5.74	89	< 0.001	5.87	70	< 0.001
mutD5 dinB	5.50	5.74	1.35	0.24	5.54	0.04	0.85
mutD5 dinB umuDC	5.84	5.74	0.80	0.37	5.59	1.6	0.21
mutD5 lexA3	5.73	5.74	0.01	0.93	5.59	0.55	0.5
MA experiments on minimal medium
mutD5	4.03	5.74	41	< 0.001	5.68	38	< 0.001
mutD5 mutL	6.88	5.74	17	< 0.001	5.81	14	< 0.001

BPS, base pair substitution; MA, mutation accumulation.

^aχ² values were calculated comparing the observed value to the expected value calculated from the ratio of coding vs. noncoding nucleotides in the MG1655 genome, which is 5.74 (Lee et al. 2012).

^bχ² values were calculated comparing the observed value to the value expected from 1000 Monte Carlo simulations using the BPS spectra of each strain.