ABSTRACT
Cyanobacteria are a primitive group of Gram-negative photoautotrophic prokaryotes having a cosmopolitan distribution thermally adapted from hot springs to the cold Arctic and Antarctic regions [1]. They were probably the rst organisms to release oxygen by splitting water during photosynthesis into the then anoxygenic environment that appeared during the Precambrian era (between 2.8 and 3.5 × 109 years ago) and thus provided a favorable condition for the evolution of aerobic life [2]. Cyanobacteria are major biomass producers both in aquatic as well as terrestrial ecosystems and are a valuable source of various natural products of medicinal and industrial importance [3,4]. In addition, their inherent capacity to x atmospheric nitrogen makes them important for rice-growing regions where they add to fertility of the rice paddy elds as natural biofertilizer [5].
