PT  - JOURNAL ARTICLE
AU  - Ophelia S. Venturelli
AU  - Ignacio Zuleta
AU  - Richard M. Murray
AU  - Hana El-Samad
TI  - Population diversification in a yeast metabolic program promotes anticipation of environmental shifts
AID  - 10.1101/002907
DP  - 2014 Jan 01
TA  - bioRxiv
PG  - 002907
4099  - http://biorxiv.org/content/early/2014/02/21/002907.short
4100  - http://biorxiv.org/content/early/2014/02/21/002907.full
AB  - Delineating the strategies by which cells contend with combinatorial changing environments is crucial for understanding cellular regulatory organization. When presented with two carbon sources, microorganisms first consume the carbon substrate that supports the highest growth rate (e.g. glucose) and then switch to the secondary carbon source (e.g. galactose), a paradigm known as the Monod model. Sequential sugar utilization has been attributed to transcriptional repression of the secondary metabolic pathway, followed by activation of this pathway upon depletion of the preferred carbon source. In this work, we challenge this notion. Although Saccharomyces cerevisiae cells consume glucose before galactose, we demonstrate that the galactose regulatory pathway is activated in a fraction of the cell population hours before glucose is fully consumed. This early activation reduces the time required for the population to transition between the two metabolic programs and provides a fitness advantage that might be crucial in competitive environments. Importantly, these findings define a new paradigm for the response of microbial populations to combinatorial carbon sources.