krōˈmāshēəm noun
Usage: capitalized
Etymology: New Latin, from chromat- + -ium
: a genus of purple sulfur bacteria (family Thiorhodaceae) that are ovoid to bean-shaped or rod-shaped, motile by polar flagella, reddish from a mixture of bacteriochlorophyll and carotenoid pigments, and widely distributed in fresh or salt water, some having been reported also from soil