THE INTERCONVERTIBILITY OF "ROUGH" AND "SMOOTH" BACTERIAL TYPES

Excerpt

The existence in certain bacterial stock cultures of two types of cells, characterized respectively by the formation on agar plates of "rough" (R) and "smooth" (S) colonies, has been demonstrated for a number of bacterial groups (Shiga bacillus, paratyphoid and typhoid bacilli, Bacterium lepisepticum, pneumococci, hemolytic streptococci, cholera vibrios and Proteus¹). Under ordinary conditions, transfers from the S and R colonies breed true. The importance of the two types of colony formation is shown by the correlation of characters: subcultures from smooth colonies form stable suspensions in salt solution, while the cells from rough colonies tend to agglutinate spontaneously. The acid agglutination optimum is higher for the S than for the R type; the S type is more virulent than the R, and there are significant serologic differences.

In the examination of more than a hundred strains in my collection of paratyphoid bacilli,² there has been in all