A bacterium was isolated which caused disease in a laboratory culture of the red alga, Rhodella reticulata. The organism was an aerobic Gram-negative rod, aflagellate and pigmented. The absorption maximum of the pigments in methanol was 460 nm. The bacterium showed hydrolytic activity towards agar and produced extracellular agarase. The organism utilized monosaccharide constituents of the polysaccharide of R. reticulata, as well as the whole polysaccharide of alga, as a sole carbon source. The bacterium was identified as Cytophaga sp. LR 2 .