EFFECT OF STORAGE ON THE NUCLEIC ACID COMPOSITION OF BAKER'S YEAST*

Open Access
Publisher Website
Google Scholar
Abstract
General changes are described in the nucleic acid content of yeast stored for 20 days under extreme conditions (35 °C). The total amount of nucleic acid increased in the first phase of 6–8 days storage. In the second phase, during which the yeast started to autolyse, the nucleic acid content diminished, first slowly and then more quickly. The quantity of acid-soluble nucleotides increased with storage. The amount of dead yeast cells is low during the first period, but starts to increase quickly during the second period. Changes in the rRNA, 5S RNA, tRNA, mRNA and DNA, fractionated on MAK columns, were investigated over a 20-day storage period. The contents of the RNA fractions increased initially during storage. The amount of rRNA attained its maximum value after 5 days, followed by DNA (7 days), then tRNA (10–12 days) and lastly 5S RNA; thereafter they all decreased. The mRNA fraction diminished rapidly: after only two days' storage the incorporation of labelled uracil into mRNA had declined by about 90%, showing that the ability to synthesize mRNA was soon lost. The short half-life of mRNA ensures its absence in yeast stored for longer periods.