A method of determining the catalase activity of bacteria

An iodine-starch method has been developed for the detection of catalase in bacteria and for measuring this enzyme's activity. The method is based on potassium iodide reduction with hydrogen peroxide to form free iodine. The bacteria are layered on starch gel, treated with hydrogen peroxide, and then with potassium iodide. The starch gel stains blue, and light areas emerge round catalase-positive bacteria; the size of these light sites helps assess the enzyme's activity. The method permits estimating the populational heterogeneity of the cultures judging from catalase activities and helps detect the mutants by catalase; it is convenient, simple, and provides reliable information on the taxonomic status of the bacteria.