Bacteria on Proboscis (IMAGE) Oregon State University Caption The arrow points at bacteria on the proboscis of this flea preserved in amber, which researchers believe may be an ancestral strain of the bacteria that causes bubonic plague. Credit (Photo by George Poinar, Jr., courtesy of Oregon State 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.