332 Mutation in Mict'o- Organisms 



A case of a similar nature has been recorded by Jacobsen (1910). 

 From a typhoid epidemic he obtained a bacillus (A) which differed 

 from a typical B. typhosus in that it refused to grow properly on the 

 Drigalski-Conradi medium^ used in the laboratory. Finally, however, 

 nodules appeared in these weakly colonies, and were found to consist 

 of individuals which grew strongly in the orthodox manner. On culti- 

 vation the latter organisms were proved to be typical B. typhosus. 

 Experiments showed that the Drigalski-Conradi medium had been 

 altered in some way by repeated autoclaving^. The altered medium 

 retarded the growth of the strain A^, which was able, however, to 

 undergo a partial mutation into strains which could grow easily in 

 the medium (B. typhosus). Jacobsen — on analogy with Massini's 

 results — ^proposes to call his original strain A by the name B. typhi 

 mutabile. The mutated form — B. typhosus — never reverted to the 

 original type (A). Jacobsen's results have been in the main con- 

 firmed by R. Muller (1911). 



Some other cognate facts may be briefly considered here. Schroter 

 and Gutjahr (1911) record the following observations. A race Y of 

 coU-typhosus-grou-p organisms cannot ferment maltose. After culti- 

 vation, however, it partially acquires the power — thus coming to 

 resemble Flexner bacilli. The Y organisms appear to behave towards 

 maltose as B. coli mutabile behaves towards lactose. They found similar 

 changes in other related organisms. For example, Shiga-Kruse bacilli 

 may acquire the power of splitting both maltose and saccharose when 

 grown in media containing these sugars. The change appears to be 

 permanent — that is, once the property is acquired by the race, it is 

 never lost. 



Sobernheim and Seligmann (1911) have isolated an organism which 

 behaves exactly like Massini's B. coli mutabile. They have confirmed 

 their results by isolating individuals by Burri's method. (See p. 330, 

 footnote.) In addition, they record that they have obtained four dif- 

 ferent pure races from one pure original race. From a coli-typhosus- 

 group organism (Haustedt) they have obtained in pure culture (1) a 

 true Gartner strain, (2) a similar strain, but differing in agglutinating 

 power, (3) a typical typhosus, and (4) a strain almost identical with 

 B. coli mutabile (Massini). 



» See p. 328 footnote. 



^ An autoclave is an apparatus used for sterilizing culture media, etc. Sterilization is 

 effected by steam under pressure. 



3 But not, of course, of the typical strains of B. typhosus. 



