WinCF Graphic, UC San Diego Health (IMAGE) University of California - San Diego Caption Oxygen stratifies bacterial communities in a cystic fibrosis lung model: Each band represents a 1mm section in bronchiole-like tubes. Coloring indicates distribution of a particular bacterial species throughout an oxygen gradient along the tube, from high oxygen at the top to low oxygen at the bottom. Pathogens, bacteria that cause health problems, distribute differently along the gradient than anaerobes, bacteria that prefer low oxygen levels and don't typically cause disease. Credit UC San Diego Health Usage Restrictions Use caption and photo credit as indicated 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.