Virulence,Electrophoresis,and Conversion Characteristics of Bact. phaseoli sojense,S and R.

Abstract

The occurrence of “Rough” and “Smooth” strains among bacteria pathogenic for plants has been reported, and the conversion of R to S forms by passage through plants described. 1 The conditions associated with conversions of R to S and of S to R strains have been further investigated.

S to R Conversion: The culture of Bact. phaseoli sojense used in these experiments grows best at a temperature of 30° C. At this temperature, R and S strains are stable even after 5 months'incubation. When held at higher temperatures (up to 37.5° C.) S strains are transformed (not completely) to R. Growth in nutrient broth of hydrogen ion concentration between pH = 5.2 and 8.8 is without effect in changing the colony form. Cultivation in broth containing 1 to 20% homologous (S) anti-serum (rabbit) results in conversion of S to R (not completely); but in broth containing the heterologous (R) anti-serum, normal serum or no serum, no change is effected. If rapid serial transfers be made in broth containing 10% anti-S serum, the conversion of S to R forms is rapidly effected and is carried almost but not quite to completion. Similar conversion is effected by growth in peptone water containing from 2 to 15% peptone and is probably complete in the 10-15% solutions. Rapid transfer in nutrient broth or on agar slants or plates was without demonstrable effect.

R to S Conversion: Normal or rapid transfers in broth or on agar slants or plates did not effect conversion. Cultivation in the presence of homologous (R) anti-serum results in rapid but not complete R to S changes and serial transfer in the presence of 10% of this serum in the broth results in nearly complete transformation of the culture; whereas growth in the broth alone or in the broth containing normal or heterologous (S) anti-serum effects no change. A striking and nearly or entirely complete conversion of R to S is effected by growth on glucose agar. This conversion does not occur in glucose broth or other fluid glucose media (except when rapidly transferred), nor in solid or fluid media containing other sugars.