Penicillin-induced Penicillin Resistance 89 



retains some inducibility might be regarded as an example of 

 this type of change; and 569/H could be considered as its 

 apogee. However, isolation of the non-inducible 569/H/l 

 from a culture of 569/H which had grown some time in casein 

 hydrolysate rather suggests that the mutation: 569->569/H 

 might be considered as "development of constitutivity " and 

 the difference between 569/H and 569/H/l might be similar 

 to that between the magno- and parvo-constitutives of the 

 5 series. No change from non-inducible to inducible peni- 

 cillinase production has yet been found. 



(2) Strains of the " 5 group " are completely insusceptible to 

 penicillinase induction. They form a family which are indis- 

 tinguishable from one another by any known criterion apart 

 from rates of penicillinase production. But they are physio- 

 logically distinct from the 569 family, differing slightly in 

 colonial morphology, in rates of fermentation of salicin and 

 starch (Sneath, personal communication) and in the type of 

 penicillinase produced. 



(3) The 5/B and 569/H constitutive penicillinases and the 

 569 (induced) penicillinase have been purified and their physico- 

 chemical and biochemical characteristics compared (Pollock, 

 Torriani and Tridgell, 1956; Kogut, Pollock and Tridgell, 

 1956). The 5/B penicillinase differs slightly but significantly 

 from the 569/H enzyme by all criteria examined (molecular 

 weight, sedimentation constant, molecular activity, electro- 

 phoretic mobility and salt solubility) while the induced 569 

 and 569/H enzyme are indistinguishable. An immunological 

 comparison [based on slopes of enzyme neutralization curves 

 in the presence of increasing quantities of a specific antibody 

 preparation partially absorbed with the induced 569 enzyme — 

 see Pollock (1956a)] has shown the 5/B and 569 enzymes to be 

 related though distinguishable, while the basal 569 (unin- 

 duced) penicillinase gives the same slope as the 569 (induced) 

 569/H and 569/H/l enzymes. 



There is clearly not enough of the " microconstitutive " 

 5 penicillinase to allow its isolation and physicochemical 

 characterization. But, as with the basal 569 enzyme, an 



