TABLE 4.

Ozone inactivation^a of L. monocytogenes after 2 min of exposure^b and CA and SOD activities

Strain and growth phase	Mean no. of CFU/ml ± SEM			Mean activity ± SEM
	4°C	24°C	37°C	CA	SOD
10403S (wild type)
Mid-exponential	5.3 ± 0.1	4.3 ± 0.4	3.7 ± 0.3	26.4 ± 2.3	72.3 ± 4.4
Early stationary	4.1 ± 0.4	3.3 ± 0.5	2.6 ± 0.1	29.3 ± 1.3	83.3 ± 2.9
Late stationary	5.5 ± 0.3	5.2 ± 0.3	4.0 ± 0.4	18.6 ± 1.7	43.7 ± 4.6
1370 (CA− SOD+)
Mid-exponential	5.7 ± 0.1	4.6 ± 0.1	4.4 ± 0.3	NDc	145.7 ± 4.8
Early stationary	5.2 ± 0.3	4.4 ± 0.3	3.8 ± 0.2	ND	157.6 ± 4.6
Late stationary	6.0 ± 0.1	5.2 ± 0.2	5.1 ± 0.2	ND	89.3 ± 7.3
DHL1 (CA+ SOD−)
Mid-exponential	6.5 ± 0.1	5.9 ± 0.1	5.5 ± 0.1	29.6 ± 2.1	ND
Early stationary	6.2 ± 0.2	5.6 ± 0.1	5.1 ± 0.4	34.4 ± 2.5	ND
Late stationary	6.7 ± 0.2	6.3 ± 0.1	5.9 ± 0.1	19.5 ± 2.9	ND

^aThe ozone concentrations at 4, 24, and 37°C were 0.30, 0.25, and 0.19 mg/liter, respectively. 

^bCells were grown in TSB–2.5% NaCl at the indicated temperatures, pelleted, and suspended in PPB prior to ozone exposure. 

^cND, none detected.