Nitrifying Activated Sludge Tank (IMAGE) DOE/Joint Genome Institute Caption Bubbling nitrifying activated sludge tank in Klosterneuburg, Austria, which was the source of the sludge samples used for microcolony sorting. This image complements the DOE Joint Genome Institute news release about the discovery of a novel group of giant viruses reported in the April 7, 2017 issue of Science. Credit Marton Palatinszky 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.