Yeast colonies: a model for studies of aging, environmental adaptation, and longevity

Abstract

When growing on solid surfaces, yeast, like other microorganisms, develops organized multicellular populations (colonies and biofilms) that are composed of differentiated cells with specialized functions. Life within these populations is a prevalent form of microbial existence in natural settings that provides the cells with capabilities to effectively defend against environmental attacks as well as efficiently adapt and survive long periods of starvation and other stresses. Under such circumstances, the fate of an individual yeast cell is subordinated to the profit of the whole population. In the past decade, yeast colonies, with their complicated structure and high complexity that are also developed under laboratory conditions, have become an excellent model for studies of various basic cellular processes such as cell interaction, signaling, and differentiation. In this paper, we summarize current knowledge on the processes related to chronological aging, adaptation, and longevity of a colony cell population and of its differentiated cell constituents. These processes contribute to the colony ability to survive long periods of starvation and mostly differ from the survival strategies of individual yeast cells.

Figure 1

(a) Development of colonies formed by laboratory strain of S. cerevisiae. Colonies develop on complex glycerol agar with Bromocresol purple, pH dye indicator with pKa of 6.3, the color of which changes from yellow at acidic pH to purple at more alkali pH. (b) Upper part: process of colony differentiation to cells with specific metabolic properties localized in upper (U cells) and lower (L cells) layers of the colony center, respectively. Viability: percentage of colony-forming cells is given. PCD: programmed cell death. Lower part: presence of subpopulations of dividing and nondividing cells.

Figure 2

Development of colonies formed by wild strain of S. cerevisiae. Localization of dividing, young nondividing, and stationary cells within the colony is shown on vertical colony cross sections. Grey lines: surface of the agar.