An Enzymatic Locus Participating in Cellular Division of a Yeast

Growing cells of a filamentous mutant of a yeast, Candida albicans, were found to accumulate and reduce tetrazolium dyes whereas cells of the parent strain, growing as a normally budding yeast, accumulated the dye but did not reduce it. In older cultures, in which rapidly metabolizable carbohydrate has been depleted, the parent strain characteristically produces filaments. These cells, growing in the absence of cellular division, also exhibit tetrazolium reduction. The filamentous mutant synthesizes cell mass at a rate almost equal to that of the parent strain and is not distinguished therefrom in fermentation ability, nutritional requirements for growth, rate of endogenous respiration, or polysaccharide composition. These facts, in conjunction with the striking differences in tetrazolium reduction, lead to the conclusion that the morphological mutant has an impairment to a cellular oxidation mechanism at a flavoprotein locus. This locus is, then, the site at which a reaction essential for cellular division, is coupled via an oxidation-reduction to cellular metabolism. Preliminary evidence is presented providing good indication that uncoupling of cellular division (by genetic block) in the mutant or in the parent (by substrate exhaustion) results from impairment to a dissociable metal chelate mechanism which normally couples a reaction essential to cellular division to flavoprotein oxidation.