Synechococcus (sin-eck-owe-cock-us), a rod or sausage shaped cyanobacterium (blue green alga) which comes from the upper layers of a microbial mat. The cells have terminal inclusions. Other bacteria are present in the same sample. Phase contrast. Material provided by Mike Ferris from Mushroom Spring, a thermal site in Yellowstone National Park, photograph by Mike Ferris and David Patterson.