Cider Words: Yeast Regulation

Yeast Regulation
Yeast Regulation: Upregulating and Downregulating

Yeast are single cell organisms that are seeking to survive and thrive in whatever environment they find themselves. As a single cell organism, we might be inclined to think of them as simple but, that would be a mistake. Yeast have a vast amount of processes they perform to live and even thrive in a wide range of environments. These processes form what are called pathways. Pathways are independent reactions and some of these reactions can be part of multiple pathways. The pathway a yeast cell will use is triggered by the environment in which it resides and the compounds available to it. Not all of the potential pathways can be operational at the same time. Yeast must turn some on and turn others off.

These pathways are managed by the genetic makeup of the yeast cell or genes. Genes are small segments of the DNA that define the traits or characteristics of a yeast cell. Genes define why some yeast will process malt sugars and others won’t or why some yeast produce spicy aromas and others fruity ones. Genes are a key part of the complex regulation system built into the cell. The lack of genes can enable or disable certain reactions and some yeast lose or gain genetic traits to match their environment. Beer yeasts are a great example of this situation. But, the complex genetic makeup of yeast is the true regulatory system. The genes and yeast DNA define how yeast upregulate or downregulate the reactions and pathways that it’s needs to survive and grow.

  • Upregulating: The process where a cell increases a reaction or use of a pathway. When a cell upregulates, it processes more of a given compound creating more of the desired reaction. An interesting aspect of upregulating is that too much of a compound can actually be downregulating versus upregulating. For example, too much glucose can shutdown certain glucose pathways.
  • Downregulating: The process where a cell decreases the reaction or use of a pathway. Downregulating means that the cell stops processing certain compounds by shutting down a pathway or reaction. This can happen when too much of a compound is present or there is a compound lacking. As yeast process sugar into ethanol, what we call fermentation, the ethanol is toxic to the yeast cell. To avoid killing itself, yeast will downregulate that pathway and stop producing more ethanol. That same pathway could also be downregulated if the yeast cell lacked sufficient proteins.

Fundamentally, upregulating and downregulating are how yeast adapt to their environmental conditions to try to survive. They turn on and off different pathways in order to extract as much nutrition from their environment as possible. All of this is enabled based on the DNA and genes possessed by the yeast, which highlights the importance of yeast reproduction.

Are you interested in other ways yeast adapt to their environment? Checkout some of the articles below or search yeast or reproduction on and find even more.

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