90 



M. R. Pollock 



immunological comparison with 5/B penicillinase is possible. 

 Fig. 2 shows how a partially absorbed anti-569 antibody pre- 

 paration neutralizes the 5/B enzyme and a preparation of 

 5 penicillinase (obtained from a culture supernatant fluid 

 concentrate) to give identical neutralization slopes. The 5/P 

 enzyme is likewise indistinguishable from 5 and 5/B ; whereas 

 the 569 penicillinase gives a quite different slope. Results 

 obtained (in a diff*erent experiment) with culture supernatant 



B.megateri um 496 

 749 



B.cereus 



'04 '06 



ml. antiserum 

 Fig. 2. Neutralization of different penicillinases by partially-absorbed 

 anti-penicillinase serum. 



fluids from penicillinase-producing strains of B. suhtilis and 

 B. megaterium show no neutralization whatever and indicate 

 that their enzymes are far less closely related to 569 penicil- 

 linase than those of the 5 group. 



This immunological test can therefore be regarded as a very 

 sensitive indication of probable identity. It appears reasonable 

 to conclude that within each family of strains the change in 

 rates of increase of penicillinase activity — whether occurring 

 by enzyme induction or by mutation— reflects a purely quanti- 

 tative alteration in the rates of formation of the same protein. 



