Bacterial Stroke (IMAGE) Brown University Caption This image shows how opposite rotations of the head and tail of the single-celled microbe Caulobacter crescentus creates drag, which helps dictate its swimming direction in a fluid. The other influence is a phenomenon called Brownian motion. Credit Jay Tang, Brown University Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.