Studies on the cytology of yeasts

Abstract

Much of the confusion in the interpretation of the cytological pictures observed in yeasts could be traced to the wrong assumption that cells from cultures under entirely different physiological conditions should exhibit uniform cytological behaviour. The only rational method of approach will be to investigate the nuclear behaviour under each specific cultural condition. A critical evaluation of some recent publications is presented. Photomicrographs showing the cytological pictures during the aerobic and anaerobic phases are presented to illustrate the confusion that would result if attention is confined to either of the above cultural methods, for evaluation. The cytological pictures observed in cells taken from a 24-hour agar slant are entirely different from that observed in actively proliferating cells in well aerated media. Photomicrographs and camera lucida drawings are presented as evidence that the varying number of bodies seen represent an ascending grade of endopolyploidy. It is emphasized that the behaviour of the yeast nucleus under aerobic proliferation alone should be taken as the standard for the evaluation of the changes under different cultural conditions. Endopolyploidy appears to be a specific modification to meet particular conditions of existence.