Role of Noise-Induced Cellular Variability in Saccharomyces cerevisiae During Metabolic Adaptation: Causes, Consequences and Ramifications

Abstract

The concept of genetic determinism as illustrated by the metaphors such as ‘genetic blueprint’, or ‘genetic program’ had its beginning immediately after the rediscovery of growth lag observed when bacteria were exposed to a mixture of glucose and galactose or lactose. This concept got reinforced with the discovery of the mechanisms of how lactose activates the transcription of lac operon of E. coli. According to this doctrine, genetically identical cells exposed to the same environment respond in equal measure. However, studies carried out in the past two decades in organisms ranging from prokaryotes to eukaryotes, have clearly established that genetically identical cells need not necessarily respond in an identical fashion when exposed to a given environment. It has now become amply clear that organisms can stochastically switch from one physiological state to the other, thereby resulting in a phenotypically heterogeneous population. Such exhibition of heterogeneity by a population has been, in several contexts, shown to be beneficial in a temporally changing environment. In this review, we have discussed how individual cells of a genetically identical population of Saccharomyces cerevisiae remain fit by exploiting this fascinating phenomenon of stochastic switching from one metabolic state to the other when exposed to glucose and galactose, as a source of carbon and energy. We suggest that this inherent stochastic switching seems to have been exploited for an adaptive response in a fluctuating environment.