A unicellular blue-green alga, Agmenellum quadruplicatum, and a filamentous blue-green alga, Lyngbya lagerheimíi, were grown heterotrophically in dim light with glucose as major source of carbon and possibly energy. The dim-light conditions did not support autotrophic growth. The two blue-green algae appeared to have the same metabolic block, namely an incomplete tricarboxylic acid cycle, as ha...