Purification of penicillin-induced penicillinase of Bacillus cereus NRRL 569: a comparison of its properties with those of a similarly purified penicillinase produced spontaneously by a constitutive mutant strain

We wish to express our thanks to Dr Melvin Cohn for much valuable advice during the preliminary work on methods of purification, and one of us (M.R.P.) is greatly indebted to Dr Jacques Monod of the Institut Pasteur, Paris, for the hospitality of his laboratory in which much of the earlier work on isolation ofpenicillinase was carried out. We are also grateful to Dr T. S. Work for help in the chromatographic estimation of amino acids. The photo- graphs were taken by Mr M. R.