Shedding Light on the Yeast Respiratory Oscillation: Using Luciferase and Visible Light to Investigate Biological Rhythms in Yeast

Abstract

The yeast respiratory oscillation is a 3 to 5 hour biological rhythm in some strains of Saccharomyces cerevisiae that occurs under a specific range of growth conditions during continuous culture. The cell division cycle, in addition to transcription of many genes, oscillates along with the yeast respiratory oscillation. In this work luciferase reporters were constructed for yeast that provided automated real-time luminescent evidence of cell division synchrony and rhythmic transcriptional regulation in vivo during the yeast respiratory oscillation. This non-invasive, non-destructive luminescent system for monitoring gene activity was used to show an interrelationship between the yeast respiratory oscillation and the cell division cycle. This work also showed that visible light at an intensity of less than one tenth that of full sunlight (primarily in the blue and green wavelengths) noticeably affected the amplitude and period of the yeast respiratory oscillation by interfering with photosensitive substances required for respiration.

This dissertation constitutes a series of steps within a larger quest to fully understand the nature of biological rhythms in yeast. In addition to investigating the relationship between respiratory oscillations and cell division, other questions that motivated this research were, “Is the respiratory oscillation evidence of an endogenous biological clock?” and “Does this yeast biological rhythm shown in continuous culture exist in nature?” To pursue answers to these and related questions, a number of techniques and investigations involving the production and perception of light were used. This dissertation revolves around the use of light for exploring the biology of yeast; from developing bioluminescent yeast that report gene activity, to studying effects of visible light on yeast respiration and growth, to developing a low cost fluorescent excitation light source for use in microscopy.