Bacteria in the soil play key role in recycling matter in to useful nutrients which can be used by growing plants. This process of recycling matter in the soil by living organisms is called biogeochemical cycle. Bacteria are improving plants growth in other ways too, for example bacteria, such as Rhizobium, are in symbiotic relationship with the root system of some terrestrial plants. The most important elements, which allow terrestrial plants grow well, are carbon, phosphorus, sulphur and nitrogen. Bacteria play crucial role in recycling phosphorus, sulphur and nitrogen. This essay covers sulphur and nitrogen cycles.
Nitrogen Fixation
The fixation of the nitrogen is crucial for the terrestrial plants. Nitrogen fixation in other words is the process of conversion of atmospheric nitrogen in to a form that growing plants can use. A little number of conversion occur in lightning strikes, all the rest is done by bacteria. Nitrogen fixation is done by many types of cyanobacteria, which are photosynthetic, and various types of non-photosynthetic bacteria, for example Azotobacter, and actinobacteria. In order to fix nitrogen these bacteria consume large amounts of ATP and an enzyme called nitrogenase. To be more detailed: “This process occurs in three steps. The first step is that nitrogenase binds to a molecule of nitrogen gas. In the second step, the bound nitrogen is reduced by the addition of two hydrogen atoms, a reaction powered by the breakdown of ATP. Such a reduction occurs three times, with the addition of a total of three hydrogen atoms to each nitrogen atom. In a third and final step, two molecules of ammonia (NH3) are released and dissolve in cell water to form ammonium ions. The nitrogenase enzyme is then free to bind more nitrogen gas.”(Brooker et al, 2008) Figure 1 – The biological process of nitrogen fixation (Brooker et al, 2008)
As it was mentioned in introduction there are a number of symbiotic