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Abstract
Summary: Supernatant fluids from 5-day cultures in skim milk nutrient broth of 62 strains of Serratia marcescens, 24 of S. liquefaciens, 20 of S. plymuthica and 22 of S. marinorubra, together with 27 representative cultures of other genera, were submitted to agar gel electrophoresis. Proteinase activity was demonstrated by the casein-precipitating reaction. Serratia marcescens produced one to four cathodic proteinases and the patterns were in good accord with the classification of strains into biovars. Serratia liquefaciens often produced anodic and cathodic proteinases with differences between some biovars. Serratia plymuthica strains produced one common cathodic proteinase but no anodic proteinase. Each of the three biovars of S. marinorubra produced a specific proteinase. Other bacteria in the study (Erwinia carotovora, Erwinia chrysanthemi and Aeromonas hydrophila) produced proteinases that differed from the Serratia enzymes in their electrophoretic mobility. The results indicate that proteinase patterns could be useful in the identification of Serratia species and biovars.
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