Baker’s yeast has a biological clock ticking too

In PNAS scientific journal (Early Edition, January 19, 2010) University of Groningen chronobiologist Prof. Martha Merrow proves that Saccharomyces cerevisiae (baker’s yeast) has all the classic characteristics of a biological clock. As Saccharomyces cerevisia has been the standard model system in genetic biology for some time now, as a consequence chronobiology now has access to a plethora of research tools and methods developed in that regard. Research into the molecular mechanisms of the biological clock will quickly gain momentum, Merrow predicts.

The biological clock is a fundamental process steering biological behaviour and physiological activity at all levels. Nearly everything in nature – from humans and animals to plants, fungi and bacteria – adjusts to the rhythm of day and night and the changing seasons. This does not involve simple switches turning processes on and off at a certain light intensity or temperature, but a biological clock – a system that generates a 24-hour rhythm from within the organism, in such a way that the rhythm can adjust to gradual changes in the environment such as the lengthening and shortening of the days.

Chronobiologists – biologists who study the biological clock – already know a great deal about the clock’s complex molecular mechanism. This knowledge stems from research into organisms which serve as genetic model systems in molecular biology. However, nothing was known about a biological clock for the most heavily researched eukaryotic model system, the single-celled organism Saccharomyces cerevisia.

To prove the presence of a biological clock, Martha Merrow put Saccharomyces cerevisia to a number of classic standard tests. She grew the yeast in a fermentor in an environment where the temperature was kept at 21°C for 12 hours and then at 28°C for 12 hours, in a 24-hour cycle. Those conditions, times and temperatures were varied in a number of experiments, where the acidity and the concentration of dissolved oxygen were used as measure of activity of biochemical processes in the yeast cells.

‘All our tests were positive,’ Merrow says. ‘We can now safely say that baker’s yeast has a biological clock.’ As a result, chronobiology can now bring a complete arsenal of powerful, recently developed DNA research tools and methods to bear. ‘Research into the molecular mechanisms of the biological clock will quickly gain momentum,’ Merrow predicts. ‘We’re preparing ourselves for a quick dash.’

Article: Zheng Eelderink-Chen, Gabriella Mazzota, Marcel Sturre, Jasper Bosman, Till Roenneberg, and Martha Merrow, A circadian clock in Saccharomyces cerevisiae, PNAS (doi:10.1073/pnas.0907902107)