Many free living bacteria and blue green algae are capable to fix atmospheric nitrogen Rhodospirillum is a free living photosynthetic anaerobic nitrogen fixing non-sulphur bacteria. It is capable of synthesizing its organic food in presence of light and in absence of 02 by a process known as bacterial photosynthesis. Beijernickici and Azotobacter are free living but aerobic nitrogen fixing bacteria. Rhizobium is a symbiotic nitrogen fixing bacteria.