Studies on the mutagenic action of chemical and physical agencies on yeasts. IV. The effect of camphor on fermenting yeast cultures

Abstract

1. The effect of camphor on fermenting yeast cultures is described. The necessity for a clear differentiation of the effect of camphor on aerobically growing cultures from that on fermenting cells is emphasized. 2. Tubes containing one, two, three, four and five drops of a known concentration of an alcoholic solution of camphor incorporated in 5 ml. of wort were inoculated with a few cells from an aerobically growing culture of the two chromosome control strain. Giant colony inoculations were carried out 24, 48, 72 and 168 hours after the commencement of the experiment without any fresh addition of camphor. 3. The first series of giant colonies indicated that camphor had induced gene mutations in several directions. In the second series the changes in the population of the control growing on an agar slant was investigated side by side with the study of the mutations induced by camphor. The changes in the population of the gene mutants in the culture of the control and that growing in the presence of one or two drops of camphor solution are not parallel. 4. Camphor accelerates the mutation rate at the locus governing the nature of sculpturing of the colony. It is suggested that stable tetraploids arise only when the doubling of the chromosome complement is preceded by a specific stabilizing gene mutation. Since camphor induces gene mutations, all tetraploids induced by camphor need not have identical genic constitution. 5. If one assumes the probability that a series of alleles at a particular locus govern the harmonious working of haploid, diploid and polyploid chromosome numbers, treatment with polyploidogens instead of doubling the chromosome complement may even lead to production of forms with reduced chromosome numbers.