Modeling Bacterial Toxin Guns (IMAGE) California Institute of Technology Caption A structural model of a dynamic machine, called a Type IV secretion system, used by many bacteria in order to inject toxic molecules into cells and also to spread genes for antibiotic resistance to fellow bacteria. Credit Caltech Usage Restrictions Must use image credit 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.