If I were to take bakers yeast and put it in medium of minimal sugar(whatever quantity that would be) and rice(for a source of starch), could the yeast have a "evolutionary leap" and adapt to use the starch in its environment? I remember reading something similar in a report of E.coli bacteria and citrate adaption, under the heading: Catching evolution red-handed.

The passages in question are so:

"Every night, the bacteria run out of the sugar glucose and go dormant. The following day around noon, a researcher plunges a pipette in and sucks up 1% of the culture to inoculate a fresh flask. Those faster at gobbling up glucose will send more of their descendants to the following day's pipette and, after a few weeks, descendants of the fastest one will be the only ones transferred as the mutation 'sweeps' to fixation."

Under the heading: The rise of Escherichia erlenmeyeri, (bold emphasis mine).

"One morning, at the turn of generation 33,127 according to the lab's log book, a massive increase in turbidity was recorded on the vial labelled Ara-3. The sugar-starved bacteria had suddenly 'discovered' a vast new source of carbon by importing citrate, a pH buffer that had been in the growth media all along, and it sent the population size through the roof. "

So if I understand this correctly, there is evolution going on through the differential reproductive success of the bacteria, via their fitness which is affected by the glucose levels?

This "pressure" caused a type of "hopeful monster" in the form of Escherichia erlenmeyeri, the bacteria that could metabolize citrate, in which it didnt have the means to do so before.

So then could I replicate this concept with baker's yeast and starch metabolism and hope for similar results hypothetically? Or am I misunderstanding this?

  • 2
    $\begingroup$ You might also want to consider going with a molecular biology supplier... I wouldn't think that quality control on baker's yeast would be sufficient to be starting with a single strain, or have a sequenced genome. $\endgroup$ – AMR Sep 30 '15 at 2:53

Keep in mind that the citrate utilizing strain appeared after over a decade. Also, Escherichia coli could always metabolize citrate, but the citrate transporter that brings it into the cell is only expressed under anaerobic conditions [1]. The strain that evolved to import citrate under aerobic conditions had a duplication of the transporter gene which put it under the control of a different promoter that drives expression under aerobic conditions [2]. Baker's yeast doesn't have amylase or debranching enzyme genes [3], so a similar evolutionary mechanism cannot occur. Developing such enzymes de novo doesn't seem trivial, but perhaps the enzymes involved in glycogen metabolism can be repurposed. The only way to know is to try.


  1. Blount et al., 2008
  2. Blount et al., 2012
  3. Ostergaard et al., 2000

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