scholarly journals Selection by UV Mutagenesis and Physiological Characterization of Mutant Strains of the Yeast Saprochaete suaveolens (Former Geotrichum fragrans) with Higher Capacity to Produce Flavor Compounds

2021 ◽  
Vol 7 (12) ◽  
pp. 1031
Author(s):  
Melissa Tan ◽  
Yanis Caro ◽  
Alain Shum Cheong Sing ◽  
Héloïse Reiss ◽  
Jean-Marie Francois ◽  
...  
Keyword(s):  
Uv Mutagenesis ◽  
Yeast Saccharomyces Cerevisiae ◽  
Unsaturated Esters ◽  
Physiological Characterization ◽  
Industrial Sectors ◽  
Dragon Fruit ◽  
Hydratase Activity ◽  
Branched Chain ◽  
Coa Hydrolase

Yeast volatile organic compounds (VOCs), i.e. low molecular weight organic acids, alcohols and esters, are considered as potential and sustainable sources of natural aromas that can replace commonly used artificial flavors in food and other industrial sectors. Although research generally focuses on the yeast Saccharomyces cerevisiae, other so-called unconventional yeasts (NCY) are beginning to attract the attention of researchers, particularly for their ability to produce alternative panels of VOCs. With this respect, a Saprochaete suaveolens strain isolated from dragon fruit in Reunion Island was shown to produce α-unsaturated esters from branched-chain amino acids (BCAAs) such as isobutyl, isoamyl or ethyl tiglate, which are rarely found in other yeasts strains. Given that β-oxidation allows the growth of S. suaveolens on BCAAs as sole carbon source, we developped a method based on UV mutagenesis to generate mutants that can no longer grow on BCAAs, while redirecting the carbon flow towards esterification of α-unsaturated esters. Among the 15,000 clones generated through UV irradiation, we identified nine clones unable to grow on BCAAs with one of them able to produce eight times more VOCs as compared to the wild-type strain. This higher production of α-unsaturated esters in this mutant strain coincided with an almost complete loss of enoyl-CoA hydratase activity of the β-oxidation pathways and with a twofold increase of acyl-CoA hydrolase with not significant changes in the enzymes of the Ehrlich pathway. Moreover, from our knowledge, it constituted the first example of VOCs enhancement in a microbial strain by UV mutagenesis.

PHYSIOLOGICAL CHARACTERIZATION OF ADAPTIVE CLONES IN EVOLVING POPULATIONS OF THE YEAST, SACCHAROMYCES CEREVISIAE

Genetics ◽  
1985 ◽  
Vol 110 (2) ◽  
pp. 173-185
Author(s):  
Julian Adams ◽  
Charlotte Paquin ◽  
Paul W Oeller ◽  
Lester W Lee
Keyword(s):  
Glucose Uptake ◽  
Continuous Culture ◽  
Growth Parameters ◽  
Maximum Growth ◽  
Maximum Growth Rate ◽  
Yeast Saccharomyces Cerevisiae ◽  
Adaptive Mutations ◽  
Physiological Characterization ◽  
Evolving Populations

ABSTRACT Populations of a diploid strain of S. cerevisiae were grown in glucose-limited continuous culture for more than 260 generations. A series of seven sequential adaptive changes were identified by monitoring the frequency of cycloheximide resistance in these populations. Samples were taken from the continuous cultures following each adaptive shift and characterized physiologically to determine (1) the range of phenotypes that can be selected in a precisely defined constant environment and (2) the order and predictability of the occurrence of the adaptive mutations in evolving populations. The clones were characterized with respect to the growth parameters, maximum growth rate, saturation coefficient and yield, as well as for changes in cell size and geometry and rate of glucose uptake. The maximum growth rates of the seven adaptive clones were very similar, but in contrast the saturation coefficients differed substantially. Surprisingly, not all clones showed reductions in the saturation coefficients, in comparison to the immediately preceding clones, as would be predicted from classical continuous culture kinetics. In addition, yield estimates first increased and then decreased for later isolated adaptive clones. In general, the results suggest epistatic interactions between the adaptive clones, consistent with earlier published results. The rate of glucose uptake, as measured by 14Cxylose uptake, increased dramatically after the selection and fixation of seven adaptive clones. Progressive decreases in cell volume and changes in cell geometry, resulting in increased surface area to volume ratios, were also observed in the adaptive clones, but these changes were not always seen in other haploid and diploid yeast populations evolving under the same conditions. Such changes may be easily explainable in terms of the characteristics of the glucose-limited environment. The significance of the results to the evolution of microorganisms under nutrient-limiting conditions is discussed.

Molecular and physiological characterization of Arabidopsis‐Colletotrichum gloeosporioides pathosystem

2021 ◽  
Author(s):  
Mengze Gao ◽  
Miting Wan ◽  
Liyun Yang ◽  
Meng Zhao ◽  
Xiaojin Liu ◽  
...  
Keyword(s):  
Colletotrichum Gloeosporioides ◽  
Physiological Characterization

Biochemical and nutritional characterization of dragon fruit (Hylocereus species)

2021 ◽  
Vol 353 ◽  
pp. 129426
Author(s):  
M. Arivalagan ◽  
G. Karunakaran ◽  
T.K. Roy ◽  
M. Dinsha ◽  
B.C. Sindhu ◽  
...  
Keyword(s):  
Dragon Fruit

scholarly journals Direct Estimate of the Mutation Rate and the Distribution of Fitness Effects in the Yeast Saccharomyces cerevisiae

Genetics ◽  
2001 ◽  
Vol 159 (2) ◽  
pp. 441-452
Author(s):  
Dominika M Wloch ◽  
Krzysztof Szafraniec ◽  
Rhona H Borts ◽  
Ryszard Korona
Keyword(s):  
Spontaneous Mutation ◽  
Fruit Fly ◽  
Diploid Cell ◽  
Induced Mutations ◽  
Direct Estimate ◽  
Yeast Saccharomyces Cerevisiae ◽  
Related Trait ◽  
First Time ◽  
Defective Mismatch Repair

Abstract Estimates of the rate and frequency distribution of deleterious effects were obtained for the first time by direct scoring and characterization of individual mutations. This was achieved by applying tetrad analysis to a large number of yeast clones. The genomic rate of spontaneous mutation deleterious to a basic fitness-related trait, that of growth rate, was U = 1.1 × 10−3 per diploid cell division. Extrapolated to the fruit fly and humans, the per generation rate would be 0.074 and 0.92, respectively. This is likely to be an underestimate because single mutations with selection coefficients s < 0.01 could not be detected. The distribution of s ≥ 0.01 was studied both for spontaneous and induced mutations. The latter were induced by ethyl methanesulfonate (EMS) or resulted from defective mismatch repair. Lethal changes accounted for ~30–40% of the scored mutations. The mean s of nonlethal mutations was fairly high, but most frequently its value was between 0.01 and 0.05. Although the rate and distribution of very small effects could not be determined, the joint share of such mutations in decreasing average fitness was probably no larger than ~1%.

scholarly journals Cloning and characterization of four SIR genes of Saccharomyces cerevisiae.

1986 ◽  
Vol 6 (2) ◽  
pp. 688-702 ◽  
Author(s):  
J M Ivy ◽  
A J Klar ◽  
J B Hicks
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Blot Analysis ◽  
Transcriptional Control ◽  
Genomic Library ◽  
Yeast Saccharomyces Cerevisiae ◽  
Mating Type Genes ◽  
Rna Blots

Mating type in the yeast Saccharomyces cerevisiae is determined by the MAT (a or alpha) locus. HML and HMR, which usually contain copies of alpha and a mating type information, respectively, serve as donors in mating type interconversion and are under negative transcriptional control. Four trans-acting SIR (silent information regulator) loci are required for repression of transcription. A defect in any SIR gene results in expression of both HML and HMR. The four SIR genes were isolated from a genomic library by complementation of sir mutations in vivo. DNA blot analysis suggests that the four SIR genes share no sequence homology. RNA blots indicate that SIR2, SIR3, and SIR4 each encode one transcript and that SIR1 encodes two transcripts. Null mutations, made by replacement of the normal genomic allele with deletion-insertion mutations created in the cloned SIR genes, have a Sir- phenotype and are viable. Using the cloned genes, we showed that SIR3 at a high copy number is able to suppress mutations of SIR4. RNA blot analysis suggests that this suppression is not due to transcriptional regulation of SIR3 by SIR4; nor does any SIR4 gene transcriptionally regulate another SIR gene. Interestingly, a truncated SIR4 gene disrupts regulation of the silent mating type loci. We propose that interaction of at least the SIR3 and SIR4 gene products is involved in regulation of the silent mating type genes.

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