Utilization of organic substrates by two filamentous cyanobacteria under various growth conditions.

Two filamentous cyanobacteria Calothrix marchica Lemm. var. intermedia Rao and Scytonema schmidlei De Toni grew heterotrophically in light with or without DCMU and in the dark when supplemented with glucose, fructose or sucrose. Galactose, mannitol and sorbitol were utilized less efficiently. Mannose, xylose and organic acids did not support the heterotrophic growth of both the cyanobacteria. By continuous incubation and sub-cultivation in sucrose supplemented medium in the dark, heterotrophic adapted strains of the organisms were produced. These strains, in contrast to the light pre-treated ones, readily utilized the exogenous substrate as evidenced by increase in growth and the total nitrogen content of the cultures.