Index >> Nitrogen Fixation by Free Living Blue-Green Alage >> General Aspects

General Aspects

Blue-green algae constitute an important group of microorganisms Capable of fixing atmospheric nitrogen. They comprise unicellular, colonial and filamentous types. Some fossil forms have also been discovered which date back to pre-cambrian periods.

Most of the nitrogen­ fixing blue-green algae belong to the orders Nostocales and Stigonematales under the genera Anabaena, Anabaenopsis, Aulosira, Chlorogloea, Cylindrospermum, Nostoc, Calothrix, Scytonema, Tolypothrix, Fischerella, Hapalosiphon, Mas­tigocladus, Stigonema and Westiellopsis. In pure cultures, blue-green algae fix varying amounts of nitrogen ranging from 5.2 to 14.48 mg/100 ml of the medium, depending upon the incubation time.