Chloroflexus (cloe-row-flecks-us) is a filamentous green prokaryote, but not a cyanobacterium. It is common in lower reddish regions of some of the microbial mats which cover the sediments at some of the thermal sites. This is a small piece of such a mat. Material provided by Mike Ferris from Mushroom Spring, a thermal site within Yellowstone National Park, photograph provided by Mike Ferris and David Ward.