Molecular characterisation of a <i>Saccharomyces cerevisiae</i> strain that grows without vitamin additions

<p dir="ltr"><i>Saccharomyces cerevisiae </i>requires carbon, nitrogen, sulphur, phosphorus, metal ions, and vitamins to grow. Some strains of <i>S. cerevisiae </i>are capable of synthesising their own vitamins, however, cell growth is slow when compared to conditions containing exogenous vitamin additions. Using a long-term adaptive laboratory evolution approach, a strain of yeast has been previously developed which can grow rapidly without the addition of vitamins. Vitamin drop-out media was used to determine cell growth in the presence and absence of different B vitamins. Results showed biotin to be the key requirement for yeast growth. The main aims of this project were to characterise the phenotypic nature of biotin biosynthesis in the biotin-prototrophic <i>S. cerevisiae </i>strain and to determine its genomic and transcriptomic nature. To achieve these aims, the novel diploid vitamin-independent yeast was sporulated and its’ haploids isolated and screened for their ability to grow without vitamin additions. DNA and RNA were extracted from the chosen haploids alongside two vitamin-dependent laboratory strains X2180, and CEN.PK. Sequencing revealed substantial changes in the biotin synthesis pathway including additional copies of <i>BIO1 </i>and <i>BIO6 </i>in the vitamin-independent haploids. RT-qPCR analysis revealed biotin genes to be ssubstantially overexpressed in vitamin-independent haploids compared to biotin-dependent laboratory strains.</p>