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The Use of Proteorhodopsin by Microorganisms

Though many of the game theory examples discussed in class involved economic driving forces, the applications of game theory can be expanded to explain biological microorganisms, where the payoff for achieving the best possible outcome results in a “survival of the fittest” situation, causing the better, more desired traits possessed by the microorganism to become more common while the less useful ones die out. Microorganisms typically have many survival mechanisms present; I will discuss proteorhodopsin (, a simple mechanism used by basic microorganisms to harness the energy from light.

Though proteorhodopsin is a common energy generation mechanism found in many ocean dwelling microorganisms, it is not the best or most efficient source of power for a microorganism. In fact, if there are nutrients in the surrounding environment, the microorganism will suppress proteorhodopsin, only using it if the organism is under starvation conditions. For this reason, the use of proteorhodopsin can be thought of as an “Anti-Coordination” game, where either the proteorhodopsin is on and being used while there are no other sources of energy, or it is off and another energy source is being used. If both proteorhodopsin and an additional energy source are being used by the cell at the same time, or neither is being used by the cell, the overall creation of energy for the organism is actually hindered, and the growth of the microorganism is impeded, which could potentially result in the death of the cell. The use of other, more efficient energy sources, and suppressing proteorhodopsin can be thought of as a pareto-optimal strategy, while the use of proteorhodopsin is a secondary, less desirable Nash Equilibrium (though it is still more desirable than cell death).  By applying a form of game theory to its power generation, a microorganism can optimize growth and increase its chance of survival.


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