A mutant of Saccharomyces cerevisiae temperature sensitive for flocculation. Influence of oxygen and respiratory deficiency on flocculence

Abstract

A flocculent strain of Saccharomyces cerevisiae, containing the dominant gene for flocculence FL04, was mutagenized with N-methyl-N'-nitro-N-nitrosoguanidine. Non-flocculent mutants were isolated with a selection procedure based on the slower sedimentation of non-floceulent cells. One closer studied mutant was due to an unlinked suppressor mutation for FL04. This suppressor gene is designated sufl. The gene sufl is neither centromere linked nor linked to his4 or the mating type locus. The gene sufl behaves as a recessive in some diploids and as a dominant in others, illustrating the genetic complexity of the flocculation phenomenon. The mutant was found to be non-flocculent after growth at 30~ whether aerated or not. At 22~ the mutant was flocculent in the absence of aeration during growth, but non-flocculent with aeration or supplementation of the growth medium with ergosterol and unsaturated fatty acids. None of several inhibitors of mitochondrial functions had any effect on the expression of flocculence. A number of petites induced in the mutant strain with ethidium bromide had altered flocculation phenotypes. A method for measuring flocculence using the spectrophotometer is described.

Isolation and characterization of a polypeptide absent from non-flocculent mutants of Saccharomyces cerevisiae

“…Six out of six asci showed 2:2 segregation for flocculence revealing that the mutation causing nonflocculence apparantly has taken place in a single gene. Thirdly, it was of interest to see if this mutation was different from fsul (9). To test this, C77-M24-23 which is FL04, fsul, was crossed to C77-S49B-IA (Table I), which is also FL04 and carries the suppressor mutation present in C77-M24-13.…”

“…In an earlier paper the isolation of non-flocculent mutants from a Saccharomyces cerevisiae strain containing the dominant gene for flocculence FL04 was described (9). One of these mutants was characterized genetically and non-flocculence was shown to be due to an unlinked suppressor of FL04.…”

Mutants in the biosynthesis of isoleucine in a non-mating, non-sporulating brewing strain of Saccharomyces carlsbergensis

“…Mutants were derived as described below. Media have been described (7,9). Growth in liquid cultures was with shaking at 30~ unless stated otherwise.…”

“…Treatment of cells with 0.7 ~M-N-methyl-N'-nitro-N-nitrosoguanidine was as described (9). Then the cells were washed twice in 3 mM-EDTA, pH 6.5, suspended and diluted in the same buffer, and different dilutions were plated directly onto minimal medium containing different concentrations of thiaisoleucine as will be indicated, Colonies were picked, single colonies reisolated and suspensions retested for resistance to thiaisoleucine on minimal plates with a paper strip containing 3 mg of the drug placed perpendicularly onto the streaks of cells.…”

Mitochondrial Associated Yeast Flocculation -The Effect of Acetylsalicylic Acid

“…Thus, literature suggests that mitochondrial function and yeast flocculation is interrelated 11,21,33,35 . The importance of mitochondrial function in yeast flocculation has also been further demonstrated by the use of drugs (i.e., antimycin A, ethionine) that inhibit mitochondrial function 9,18,27 and by cells that carry deletions in mitochondrial genes 16 and petite (respiratory deficient) mutants 10,17 .…”