Oldest Known Protein Knot (IMAGE) DOE/Argonne National Laboratory Caption This image of a knotted protein comes from a microorganism called methanobacterium thermoautotrophicum that breaks down waste products and produces methane gas. This was the first structure of the most ancient type of single-celled organism – archaebacterium. Protein-folding theory previously held that forming a knot was beyond the ability of a protein; as technology improves, biologists are determining higher-quality images of structures. Researchers used the powerful X-rays at the Advanced Photon Source at Argonne to determine the protein's structure. Argonne National Laboratory image. Credit Courtesy: Argonne National Laboratory Usage Restrictions Image available for use with an Argonne acknowledgement. Image may not be used for advertising or other commercial purposes, or in such a way as to imply an endorsement of any product or service by Argonne National Laboratory. 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.