Bacterial Stroke (image) Brown University Share Print E-Mail 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 Share Print E-Mail 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.