Epilogue

Abstract

I have told you some things about a free-living organism only one micron in size. It is equipped with sensors that count molecules of interest in its environment, coupled to a readout device that computes whether these counts are going up or down. The output is an intracellular signal that modulates the direction of rotation of a set of rotary engines, each turning a propeller with variable pitch. Each engine (or motor) is driven, in turn, by several forcegenerating elements (like pistons), powered by a transmembrane ion flux. In addition to a gear shift (labeled forward and reverse but prone to shift on its own) there is a stator, a rotor, a drive shaft, a bushing, and a universal joint.