Isolation and molecular characterization of edible Spirulina species under different abiotic stress and evaluation of their food supplements

Abstract

1.1 Introduction newlineCyanobacteria are the most diverse group of prokaryotes with context to newlinenumber of species, type of habitat, morphology and physiological properties newline(Houmard, 1994). Since they appeared at least 3.3-3.5 billion years ago when the newlineearth experienced periods of extreme variations in temperature, CO2 and O2 levels newline(Giordano et al., 2005) and inhabit many different and extreme environments newlineranging from aquatic to terrestrial as well as hot springs, hypersaline waters, newlinedeserts, and polar regions (Whitton and Potts, 2000). Thus, regarded as ancient and newlinediverse group of photosynthetic nitrogen fixing microorganisms, among all the newlinephotosynthetic organisms. The diverse distribution of cyanobacteria indicates a newlinehigh degree of biological adaptation, which has enabled them to flourish and newlinecompete effectively in nature (Burja et al., 2002). This broad habitat range is due to newlinethe fact that they evolved PS II reaction center that can extract electron from water newlineand thus are not limited to environments with other reduced electron donors, as are newlineother non-oxygenic photosynthetic prokaryotes. In fact, cyanobacteria seem to be newlineable to establish competitive growth in almost any environment that has water and newlinesun light. The diversity and adaptability of cyanobacterial species is also in no small newlinepart due to the fact that they have withstood the challenges of evolutionary newlineenvironmental changes. These temporal and spatial variations have been the driving newlineforce for the evolution and acquisition of many genes and physiological properties newlinewhich have enabled successful growth in the diverse range of environments newlineoccupied by cyanobacteria today (Badger et al., 2006). newline