The sugars dwelling in cellulosic biomass are the target of many alternative fuel schemes, but they can be difficult to get to and even more difficult to process into the fatty acids that we need to make biofuels. E. coli has long been known to synthesize fatty acids efficiently, but natural processes make harvesting those acids particularly difficult. Researchers would like E. coli to biosynthesize indefinitely, but like any organism trying to remain competitive in nature, E. coli doesn't waste energy manufacturing more fatty acids than it needs to survive.