TABLE 2.

Contributions of σ^B to survival under acid and oxidative stress conditions for all four L. monocytogenes lineages

Lineage	Death rate (log CFU/h) at pH 2.5			Death (log CFU) with 13 mM CHP
	Wild typea	ΔsigB strainb	P valuec	Wild typed	ΔsigB straine	P valuef
I	3.95 ± 0.93	6.62 ± 0.66	0.0004	1.27 ± 0.04	2.10 ± 0.23	0.0225
II	1.75 ± 0.49	6.76 ± 0.79	<0.0001	1.10 ± 0.08	2.57 ± 0.12	<0.0001
IIIA	4.02 ± 2.23	5.74 ± 1.89	0.2920	1.14 ± 0.22	1.74 ± 0.40	0.0827
IIIB	3.65 ± 0.77	6.37 ± 0.73	0.0047	1.38 ± 0.30	2.09 ± 0.22	0.0291

^aAverage death rate (± standard deviation) for wild-type parent strain exposed to pH 2.5 for 1 h.

^bAverage death rate (± standard deviation) (log CFU/h) for isogenic ΔsigB strain exposed to pH 2.5 for 1 h.

^cP value for the time-strain interaction. A P value of <0.05 indicates there that was a significant difference in the average death rate between the wild-type and isogenic ΔsigB strains.

^dAverage death value (± standard deviation) (log CFU) for wild-type parent strain after 15 min of exposure to 13 mM CHP.

^eAverage death value (± standard deviation) (log CFU) for isogenic ΔsigB strain after 15 min of exposure to 13 mM CHP.

^fP value for one-sided t test. A P value of <0.05 indicates that there was a significant difference in the average death value between the wild-type and isogenic ΔsigB strains.