Don't be fooled: Yeast have two growth spurts!
Did you know that the traditional S-shaped growth curve in microbiology is terribly inaccurate? It's inaccurate for many reasons, but the reason I want to discuss today is that some microbes have multiple growth spurts - like two "S"s ontop of each other. For example, when there are two sources of sugar in the media, the microbes will first consume the more accessible sugar, and then after a pause to reconfigure their metabolism, and then start to consume the second source of sugar. This leads to two growth spurts, and hence two "S"s.
Interestingly, yeast have another trick up their sleeves (cell membranes?). The consumption of sugar, like glucose, gives yeast a large initial spurt of growth, as you can see in the below figure (the output of our Pioreactor). As a byproduct, the yeast expel alcohol, specifically ethanol.
This phenomenon is called the diauxic shift, and only some yeast and bacteria can achieve it. The ethanol is oxidized, which means that oxygen is needed for this second-stage of growth to occur.
The above experiment was performed using our Pioreactor. The Pioreactor can help you study the impact of media, temperature, and other variables on the diauxic shift. Have fun!
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