Use of ATP measurements by bioluminescence to quantify yeast's sensitivity against a killer toxin

An original method, based on ATP measurements by bioluminescence, is described for quantifying the killer activity induced by a killer strain in a liquid medium. The aim was to propose a more rapid and selective technique directly linked to cell response to the killer damages. The sensitivity degree of strains plays an important part in these "killer-sensitive" interactions. Until now, there are few quantitative method was accurate and selective enough to rank the strains depending on this criterion. In the first step, the thought process leading to the new quantitative method for killer activity is presented. The originality of the method is based on the measurement of the initial velocity of ATP release (V-i), induced by the action of the killer protein on sensitive cells. This criterion (V-i) was correlated to the measurement of the killer activity in liquid medium: when 0 < Vi < 0.17 mumol l(-1) h(-1), the killer activity (%) is directly proportional to V-i; when V-i > 0.17 mumol l(-1) h(-1), the killer activity remained constant (85 +/- 3%). Then, this method was used to classify some commercial yeasts (four sensitive or neutral strains and four killer strains) depending on either their intrinsic sensitivity to a killer toxin or their killer power against a sensitive strain chosen as a reference. (C) 2003 Elsevier B.V. All rights reserved.