Azotobacter

Azotobacter are a type of bacteria that are normally oval or spherical in shape. Azotobacter species are commonly found in soil, sediments and water. Azotobacter grows well at approximately at pH range of 7 to 9, between neutral and alkaline. Azotobacter will die if they are in an environment below the pH 6.
Nitrogen fixation can be defined as the removal of nitrogen from the environment in its molecular form (N2) to create nitrogen compounds that are helpful for other biological processes. Azotobacter species are nitrogen-fixing bacteria (which convert atmospheric nitrogen into ammonia. Azotobacter species are classified as one of the non-symbiotic nitrogen fixation bacteria (free-living bacteria in the soil).
Azotobacter aids to boost plant development and increase soil nitrogen level through nitrogen fixation by using carbon for its metabolism. Optimal calcium nutrient concentrations are required for Azotobacter to develop more rapidly and have the capacity to fix nitrogen (Iswaran and Sen, 1960) but higher nitrogen concentrations have a negative impact on Azotobacter activity (Soleimanzadeh and Gooshchi, 2013). Since more than a century ago, the genus Azotobacter has been utilised as a biofertilizer (fertiliser that contains living microorganisms) (Gerlach &amp; Vogel, 1902).