Bacteria Designed to Reflect Sound Waves (IMAGE) California Institute of Technology Caption This image is a transmission electron micrograph (TEM) image of a single commensal bacterium, E. coli Nissle 1917, which has been genetically engineered to express gas-filled protein nanostructures known as gas vesicles. The cell is approximately 2 micrometers in length, and the lighter-colored structures contained inside of it are individual gas vesicles. Credit Anupama Lakshmanan/Caltech Usage Restrictions Please use credit as listed. 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.