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Genetics

While it is easy to obtain mutants of bacteria, it is relatively difficult to obtain mutants of blue-green algae, particularly those of fiIamentous forms. The Work done in India by the late RN. Singh and co-workers reveal that it is Possible to obtain large number of mutants of nitrogen fixing blue-green algae such as Nostoc calcicola, N. linckia, Cylindrospermum maius and Gloeotrichia ghosei. Genetic recombinations and transformations among strains of Anacystis nidulans have also been obtained which neither possess heterocysts nor exhibit nitrogenase activity.

On the contrary, mutants capable of fixing blue-green algae. Three classes of genes important in heterocyst differentiation and nitrogen fixation have been cloned. They are nif genes codi8ng for structural components of nitrogenase, glutamine synthetase and ribulose biphosphate carboxylase. Differences in the organization of nif genes between Anabaena and Klebsiella have been demonstrated.