TEMPERATURE AND pH-DEPENDENT CHANGES OF ELECTROPHORETIC MOBILITY OF PASTEURELLA PESTIS

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Abstract
Virulent and nonvirulent strains of P. pestis showed a decrease in their electrophoretic mobility (E.M.) from -1.04 to -0.46 [mu]/sec/volt/cm (average) when incubated in Englesberg casamino medium for 2-3 hrs. at temperatures above 35[degree]C and pH''s below 7.0. The decrease in E.M. was preceded by a lag period of about 60-90 min. and progressed gradually until a fixed value was reached. The rate of the E.M. change increased with increase of temperature from 35[degree]C to 38[degree]C and decrease of pH from 6.7 to 6.0. E.M. changes occur only in aerated cultures and have never been observed under anaerobic conditions. An energy source is required and the change is inhibited by 2,4-dinitrophenol. Chloramphenicol revers-ibly inhibits the mobility change. In the presence of 8-azaguanine the E.M. change occurs only in cells incubated under specific conditions. Penicillin had no effect. Incubation of changed cells with trypsin resulted in a partial reversion of the E.M. change, whereas chymotrypsin and lysozyme had no effect. The above results suggest that we are dealing with the synthesis of a surface component, possibly a protein, which is responsible for the E.M. change. Since no correlation was found between the ability of different P. pestis strain to synthesize VW antigens or fraction I and to undergo the E.M. change, this surface component may be a hitherto undescribed protein.