>what will happen to all of the microorganisms which spent a great deal of energy evolving ways to metabolize plastics that suddenly lose that source of energy?

>what will happen to all of the microorganisms which spent a great deal of energy evolving ways to metabolize plastics that suddenly lose that source of energy? As the article implies, microorganisms evolve relatively quickly. So the answer is, they would evolve to consume another source of energy. (As has happened for the subjects of the article in the opposite direction.)