NONSPORULATING, RESPIRATION-DEFICIENT VARIANTS OF SACCHAROMYCES PASTORIANUS INDUCED BY CYCLOHEXIMIDE

Lomander, L. (Gothenburg University, Gothenburg, Sweden), and K. Gundersen. Nonsporulating, respiration-deficient variants of Saccharomyces pastorianus induced by cycloheximide. J. Bacteriol. 86:956-965. 1963.-When grown on cycloheximide-containing solid medium, Saccharomyces pastorianus gave rise to rough colonies, consisting of two morphologically and physiologically different kinds of organisms, named primary colony organisms and secondary colony organisms. The primary colony organisms were slow-growing and cycloheximide-resistant as compared with the secondary ones which, like the parent organisms, were fast-growing in the absence of cycloheximide, but were inhibited when cycloheximide was incorporated in the medium. Cell aggregates, large swollen cells, and dwarf cells were found among the secondary colony organisms. The primary colony organisms were smaller than normal cells but were larger than the dwarf cells. The primary colony organisms also proved to have lost the faculty to sporulate, whereas the secondary colony organisms sporulated like the untreated parents. In contrast to the normal organisms and the secondary colony organisms, the primary colony organisms did not consume oxygen in manometric experiments with glucose as a substrate. On solid medium without cycloheximide, the latter organisms grew considerably better in a nitrogen atmosphere than in air.