Recombinogenic activity of fresh cigarette smoke in Saccharomyces cerevisiae.

A procedure for determining the effect of fresh cigarette smoke on gene conversion in yeast. Saccharomyces cerevisiae D7, is described. Cigarette smoke, generated by a 2-sec, 40-ml puff, once per minute, was puffed into an open-end tube. The smoke was drawn through an exposure vessel containing a continuously stirred, stationary-phase yeast cell suspension, 1-58 sec after generation. Frequency of gene conversion was estimated in samples taken at intervals after the start of exposure. Under these conditions, a five-fold increase in mitotic gene conversion in yeast strain D7 was obtained from exposure to 20 puffs of fresh whole smoke from University of Kentucky Reference Cigarettes (2R1), to 75 puffs from the gas phase of these cigarettes, and to 45 puffs from an acetate filter version (2R1F). Selective removal of genetically active components by acetate filters is suggested since the reduction in recombinogenic activity (55%) is greater than the reduction in total particulate matter yield (25%) of the cigarette. The results indicate that 1) the procedure provides a practical bioassay for determining the effects of fresh smoke on gene conversion in yeast, without external metabolic activation; 2) the gas phase of smoke has recombinogenic activity; and 3) standard acetate filters may selectively remove genetically active components of cigarette smoke.