RafaelFajardo

Normally, both Trichoderma reesei and E. coli exist in communities of other microbes, which form a complex ecosystem rich with organisms that cooperate and compete. But with just the two of them, the relationship would be simpler. Trichoderma reesei would be what’s termed a cooperator, producing material that could be used by other organisms by releasing glucose from the cellulose it digests. E. coli, in contrast, would be a cheater, leeching off the fungus without producing anything useful for it. And those properties put the system within the realm of game theory, which typically examines how people interact in situations that could involve cooperation or competition. The authors could model the system based on parameters such as how quickly a given amount of glucose led to growth and how much the E. coli could siphon off before it reduced the fitness of the fungus. They then tested their model by adding different proportions of the two species to the starting mixture. Although all populations eventually reached an equilibrium (even if it took them anywhere from 12 to 60 generations to do so), they found that a 1:1 mixture led to the most efficient production of biofuel right from the start. All told, the combined system converted cellulose to isobutanol with an efficiency of over 60 percent of the theoretical maximum. That’s not as good as you’d get if you simply fed the same E. coli glucose, but it was pretty good considering that they were starting with a material that E. coli can’t normally address.