The catalase activities of , and strains were measured. and had significantly lower activities than The percentage of catalase activity remaining after exposure of cell-free extracts from late-log-phase cells to 53°C for 50 min allowed differentiation among the three species; catalase retained 14.1 ± 7.9% (mean ± standard deviation) of its activity, retained 53.3 ± 7.4% of its activity, and catalase was very resistant and retained 82.8 ± 6.7% of its activity. Cells of all three species harvested in stationary phase exhibited higher percentages of heat-resistant catalase, and species could not be differentiated at this stage in the growth cycle. Polyacrylamide gel electrophoresis of crude extracts from late-log-phase cells produced two bands of catalase activity in both and extracts and four bands of activity in extracts stained by diaminobenzidine. These bands differed in their susceptibilities to heat inactivation and inhibition by 3-amino-1,2,4-triazole.


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