Smoothness and Roughness and Spontaneous Agglutination of Bacterium citri, Bact. medicaginis var. phaseolicola, Bact. phaseoli sojense, and Bact. tumefaciens

Abstract

A strain of Bact. tumefaciens of tested pathogenicity, when grown on potato dextrose or beef dextrose agar, produced colonies of which about 50% were either entirely wrinkled and opaque or only partially so; the remainder, smooth and translucent. After 5 days the rough colonies appeared smooth, shiny and translucent, but their opaque centers remained. On suspension of the rough colonies in distilled water or in 0.85% saline almost complete spontaneous agglutination occurred in 12 hrs., while in suspensions of the older colonies, which appeared smooth, only partial flocculation took place. It is pointed out that in Bact. tumefaciens, colony instability manifested as smoothness and roughness may possibly be correlated with variations in virulence. Less pronounced differences in smoothness and roughness of colony form were found in Bact. citri and Bact. medicaginis var. phaseolicola. In these, roughness was not correlated with spontaneous agglutinability in distilled water or in 0.85 % saline. On the other hand, such organisms as Bacillus carotovorus and B. aroideae, which do not have rough colonies, agglutinate spontaneously to some extent in 0.85% saline. Also, a change in agglutinability of Bact. phaseoli sojense took place during 3 months of culture on potato-dextrose agar. These observations indicate that these organisms are in a state of instability, and that smoothness and roughness in colony form, and lesser and greater agglutinability, are not absolutely qualitative differences, but that they possess a quantitative element.