l-Lysine Decarboxylase as a Specific Inhibitor of the Growth of a Species of Pichia*

In conjunction with our interest in single-cell protein (Coty & Leavitt, 1971), a search was made for a screen which would supply a selection pressure for the isolation of a strain of yeast capable of excreting lysine during growth on hydrocarbons. Initially, we hoped to isolate over-producers by selecting for resistance to analogue of l-lysine, but failed because none of the analogues examined, either alone or in conjunction with compounds which were used to affect yeast-wall permeability, had any effect on the growth of our yeast. The use of L-lysine decarboxylase was then examined and found to be a successful means for inhibiting growth. The results of this study and its possible implications are discussed below.