Spirulina, a spiral-shaped cyanobacterium, is one of the members of the brown mat communities found on Mammoth Terraces. This image has been selected from 'Seen and Unseen, Discovering the Microbes of Yellowstone' by Kathy Sheehan, David Patterson, Brett Leigh Dicks and Joan Henson, and published by Globe Pequot Press Image copyright: Globe Pequot Press, used under license to MBL (micro*scope).