Tuesday, September 2, 2014

"Stuck fermentation": an example of prion-based transformation

Prions are best known for their deleterious effect on higher mammals, for example, in the diseases CJD in humans and BSE in cows. Indeed, BMG LABTECH has provided some instrumenation that has helped with the analysis of these diseases (see application note #232). However, a recent article in Cell, provides an example of a prion-based change that is advantageous, at least to the bacteria and yeast involved.

S. cerevisiae plasma membrane marked with some membrane
proteins fused with RFP and GFP markers
The article entitled: 'Cross-Kingdom Chemical Communication Drives a Heritable, Mutually Beneficial Prion-Based Transformation of Metabolism' describes how bacteria can communicate with yeast to get them to use carbon-sources other than glucose when it is present.

Typically, there is a very strong preference for glucose use by yeast, when it is present. This is especially true in strains such as Saccharomyces cerevisiae which is why it has been exploited for the production of ethanol. Biologist have known for years about this 'glucose repression' circuit based in the membranes of yeast cells that blocks yeast from using other carbon sources when glucose is present.

In the current article the researchers describe how diverse bacteria can induce a stable trait, without affecting the DNA of yeast, through the production of protein-based element. This protein fits the characteristics of a prion in that it: 1) is dominant, 2) is inherited in a non-Mendelian fashion, 3) is transferred without the exchange of nuclei 4) does not involve the mitochondrial genome, and 5) employs a molecular chaperone in propagation. This provides an example of a beneficial trait induced by prions that has likely been established to increase the likelyhood of yeast and bacteria survival in a variety of challenging environments.

Although the use of this prion is beneficial to the yeast and bacteria involved it is a problem for the wine-makers of the world. However, it is believed that now that the means of communication is understood they will be able to combat 'stuck fermentation' by knocking out the bacteria that can trigger the process, avoiding the introduction of bacteria that can induce the process or using yeast strains that are capable of overpowering the bacteria.

Some information for this blog post was obtained from the Science Daily article: "Prions can trigger 'stuck' wine fermentations, researchers find"

Journal Reference: D. F. Jarosz, et al. Cross-Kingdom Chemical Communication Drives a Heritable, Mutually Beneficial Prion-Based Transformation of MetabolismCell, 2014; 158 (5): 1083