Dissociation in Bacillus salmonicida , with Special Reference to the Appearance of a G Form of Culture

Abstract

Stock cultures of the bacterium were caused to dissociate by serial subculture in 0.25% LiCl broth and by other means. Three dissociants resulted, 2 of which correspond to the R and S nomenclature in respect of differences in cultural and pathogenic properties. The 3d dissociant corresponds to the G type (Hadley). It was recovered (a) in platings from viable tubes in the LiCl broth series, during the phase of R to S dissociation, (b) by application of the Hauduroy washed-plate technique to later tubes in the same series which showed no visible signs of growth. The G forms remained relatively stable when maintained by infrequent transfer on nutrient agar; only 3 out of 22 strains reverted spontaneously to R after 12 mos. Continuous serial subculture in LiCl broth and in mold-filtrate broth resulted in reversion to R in 8 and 5 months respectively. The R forms so obtained were finally caused to revert to the pathogenic S form originally isolated from diseased fish.