Engelsk definition
A genus of anoxygenic, photosynthetic, nonmotile, spherical to slightly ovoid bacterial cells occurring singly, or in aggregates of two or four, and usually surrounded with slime. It is found in stagnant water, mud of ponds, estuaries, and microbial mats of salt marshes. (From Bergey's Manual of Determinative Bacteriology, 9th ed)