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The Cyanobacteria or blue green algae are the pioneer oxygenic phototrophs on earth whose distribution around the world is surpassed only by bacteria. Cyanobacteria and similar organisms produced most of the oxygen found in Earth's atmosphere, which implies that early photosynthetic organisms would have lived in an atmosphere that was rich in CO2 and poor O2 (David et al, 2005). It was shown that three common cyanobacterial species can grow under conditions that resemble those thought to have existed on early Earth: very high pCO2 and low pO2. Fossil evidence points to their presence in geographically diverse regions during the Precambrian (2 or more than 3.5 billion years ago). They are a large and morphologically diverse group of phototrophic prokaryotes, which occur in almost every habitat on earth. This versatility may explain the remarkable lack of morphological (and presumably physiological) change seen in 3.5- billion-year-old fossilized BGA and their modern day counterparts (Adams, 2000).