Origin of Biotypes in Pure Lines of Bacteria 191 



92 (2052) 



Observation on the origin of biotypes (microbic dissociation) in 

 pure lines of bacteria. 



By RALPH R. MELLON. 



[From the Highland Hospital, Rochester, N. Y.] 



The experiments reported show that bacterial variability can 

 be identified with the pleomorphic cycle. The strain studied 

 was a bacillus that formed giant coccoids under certain condi- 

 tions. The morphologic and staining changes occurring in these 

 are indicative of biochemic reorganization that conditions vari- 

 ability in the strain, However, variability only occurs if the 

 coccoids are transplanted to an environment that is selective 

 enough to further the changes that are indicated by the pleo- 

 morphism itself. 



In this case the pleomorphic giant coccoids when transplanted 

 at 20 C° grew after about two weeks, when usually they 

 grow best at 37° in 24 to 48 hours. Under the former 

 conditions a bacillary variant was produced instead of the orig- 

 inal bacillus. The variant was a distinct type morphologically 

 and culturally, although immunologically it agglutinated the 

 antiserum for the original bacillus better than the homologous 

 strain itself did. The titre of the latter was 640, for the variant 

 1,280. The variant also absorbed all the agglutinins from the 

 serum. 



This strain has been under observation for six years as a 

 pure line culture, and is prone to form rudimentary branching 

 forms as well as giant coccoids. The reorganization occurring 

 in the giant coccoids made possible the dissociation of the 

 branching phase as a distinct type. Pleomorphism for this strain 

 is regarded as a true life cycle, and in reality represents poten- 

 tial variation. The biologic nature of the giant coccoids is 

 shown in the following study. 



