326 Essays in Biochemistry 



nella, Staphylococcus, tubercle bacillus, Alcaligenes radiobacter, Phyto- 

 monas tumefaciens, and Brucella. However, these reports have not as 

 yet been confirmed by others and thus far cannot be used for a routine 

 study of the transforming principle. 



Besides pneumococcus, the only two species in which the transforma- 

 tion phenomenon can be repeated day after day with the same 

 reliability are Hemophilus influenzae 13 and Neisseria meningitidis. 1 * 

 Hemophilus influenzae lends itself particularly well to quantitative 

 studies on the transforming principle because of the absence of DNAase 

 from bacterial cultures. 



Features Transferable in the Transformation Phenomenon 



The feature transferred (induced) in the transformation phenome- 

 non, as originally discovered by Griffith, was the production of capsules 

 of type I, II, or III of pneumococcus; as is well known, each capsule 

 contains polysaccharide specific for its type. Further studies of 

 McCarty and Avery demonstrated that the production of capsules of 

 types VI or XIV can also be induced by using the transforming prin- 

 ciples from the cells of these types. It is probable that transformation 

 could be demonstrated for every one of the 70-odd known types of 

 pneumococcus. The feature transferred need not be limited to poly- 

 saccharide however. Austrian and MacLeod demonstrated acquisition 

 of a specific M protein through transformation in pneumococci. The 

 six capsular substances a, b, c, d, e, and / produced after the trans- 

 formation of Hemophilus influenzae 13 at first appeared to be polysac- 

 charides, but closer chemical study 15, 16 revealed that most of them 

 form a new class of immunologically active compounds, the polysugar 

 phosphates. The substance of type b is of particular interest: it 

 appears to consist of a polyribophosphate chain, as it exists in pentose- 

 nucleic acids, in which the place of the purines and pyrimidines is 

 occupied by a second similar chain, linked to the first in 1:1' glycosidic 

 linkages. The substance of type a appears to be a polyglucophosphate 

 and that of type c a polygalactophosphate. The transferable feature in 

 Neisseria meningitidis is the production of capsular substances of type 

 I or Ha which appear to be more complex than polysaccharides. Other 

 transferable features include induction of fermentation of salicin, 

 change in metabolism of glucose and lactic acid, production of mannitol 

 phosphate dehydrogenase, and change in quantity of polysaccharide 

 produced; in this last case it was suggested that the genes involved 

 form indeed a series analogous to what is known in higher organisms 

 as an allelic series. Still other transferable features include change 



