Venue: At the Gerghelim vineyard in Sicily in Italy, owned by the very Paolo Visconti of the great Busoni clan.
Mood: The sun is still bright as it is only 4 pm; children are playing hide and seek outside; women folks are curing pork meat; the men folks have their eyes glued on the telly; Inspector Montalbano is busy solving the case ‘ The shape of the water’. Amidst this hullabaloo, on the surface of red grapes, two wild yeasts meet and brood over their anxieties.
Protagonists: dois leveduras idoso
Ô¹: Did you know that we have to be observant of our children? They are taught all sorts of things at the ‘Physiology of Yeasts and Filamentous Fungi‘ meeting that was held in Lisboa in July; we must tell our kids that their primary devotion must be for our ever grateful glucose. We must be pure, unpolluted and guard our yeast race.
The second yeast was nodding its bud all the time agreeing to everything that was secreted by the vesicles of this old yeast. You see, yeasts cannot speak, hence they use exocytosis to communicate. An old yeast can have as many as 30 bud scars. With every nod, few proteins gargle out and a clever archae gobbles it immediately.
Ô²: Yes, I hear that they want us to consume cellobiose, xylose and arabinose as well. We shan’t at any cost adapt those ‘Western’ values; we have to watch our cellular volumes very carefully. We must keep our surface area to the volume ratio very high; otherwise, we shall be out competed by other archaea that are out and about. “Size zero isn’t just for the humans”, it bellows.
Meanwhile children are heard rhyming the following conducted by petite yeast which has lost its mitochondria and hence crippled:
Saccharomyces (2 beats)
Scheffersomyces (2 beats)
e Padaria Alemão (4 beats)
Ron Milo from Weismann is a man of numbers; very quickly he calculates that the surface area to volume ratio of a perfect sphere is the highest at 3 times the inverse of radius. And Yu-Jin’s group from Energy Biosciences Institute showed that yeasts can co-consume cellobiose, xylose and acetate; It was a published in ACS synthetic biology in Jan 2015.
Ô¹: Humans would like to produce ethanol from lignocellulosic materials desperately. They are afraid that the sea levels will rise and the temperature of the planet will increase beyond 2 deg C if they do not curtail the use of fossil fuels.
Ô²: Of course we have been very good in converting the sugar cane juice to ethanol very efficiently even when there is plenty of oxygen. We needn’t worry about climate change so much, don’t we ? we have seen dinosaurs die right before us, remember, when that big comet hit us? We survived. We will survive, no matter what.
In the background Gloria Gaynor’s ‘I will survive’ is superimposed on ‘Cake’s modern version of the same song.
Ô¹: Oh, Yes. I remember very well. It was some 200 million years that we separated from our ancestors and decided to duplicate our genome to improve our fitness. We were rebels then. Those days. Is it always that past is glorious? We yearn for the past, fearful of the future and lo behold, forget the present.
Ô²: Humans (be careful with those from Delft and Sweden) are looking at various ways in which we can work even more efficiently; we are working at near maximum efficiency without producing much of our progeny; indeed we have become their slaves; they do not care for us and we have to toil long hours in the fermentation vats without oxygen, without seeing the grapes, the insects, or the sky…
Gombert and Von Maris published an article in 2015 on the developments of 1G bioethanol. They discuss if it is possible to conserve free energy in conventional fermentations. They decided that yeast cells have to be coerced to spend energy thereby forcing them to produce more ethanol. They tried this with maltose and sucrose metabolism and they were very successful. Jens Nielsen’s group in Sweden is bent on making yeast cell factories.
Ô¹: CRISPR-CAS has made it easy to put multiple genes in us in single transformation. We would have so many new features that our forbearers would find it hard to identify with us.
Ô²: The problem with the lignocellulose hydrolysates is that they are nasty. First of all, they are filled with toxins that will kill us; it will drain our redox power; we will forever be spending energy to expel the acetic acid entering our pores here and a furfural coming there.
Assuming a diameter of yeast as 4.6 micrometre, gives a of surface area of 4 x pi x 2.3^2 = 66.5 square micrometre. ~ Proteins on the surface: The average diameter of surface proteins is 4.8 nm. Let us assume that the proteins are spherical and form a closely packed monolayer. In a monolayer, spherical proteins occupy a surface area = pi r^2 = 12.6 square nanometer (1 square micrometer corresponds to 1 million square nanometers). According to these calculations, the surface of a single parent cell is occupied by at most 3.3 million.
Ô¹ & Ô²: Both the yeasts tell each other that they must pray the heavens as they do not have anyone to share their predicament; the growth rates of other yeasts are becoming very low and they are quite worried with the changes that are meted out to them; somehow these two yeasts feel that they must hold on to their roots and not change; but they can’t resist for long; they will be forced to yield.
May the thermodynamic force be with them.
To be continued…