Microbiology and Nitrogen Cycle

Bacillus subtilis is a well-known phosphate solubilizing bacterium that helps convert insoluble phosphorus into a form plants can absorb.

Azospirillum is a well-known genus of nitrogen-fixing bacteria that forms associative symbiotic relationships with the roots of various grasses, including maize.

Azolla is a small aquatic fern that has a symbiotic relationship with the cyanobacterium Anabaena azollae, which lives in its leaf cavities and fixes atmospheric nitrogen.

Archaea are very important for ammonification in rhizospheres. It is a process that includes transforming organically bound nitrogen from microbial or plant biomass to ammonia.

Pseudomonas syringae colonises phyllosphere (above-ground portions of plants). It lives in the leaf ecosystem as an epiphyte and a pathogen.

Pseudomonas putida is a beneficial bacterium that solubilises inorganic phosphorus from insoluble compounds.

Perennial legume nodules are long finger-like nodules, half an inch in diameter. They can be found on alfalfa and clover. These nodules grow mostly around the tap root and live for quite a long time.

Biodegradation step of carbon cycle would suffer in the absence of heterotrophs. They are important in the carbon chain for the processes of biodegradation and decomposition under aerobic and anaerobic conditions.

Trichodesmium belongs to the genus of filamentous cyanobacteria. It performs almost half of the nitrogen fixation in marine systems on a global scale.

The direct reduction of sulphate ions to hydrogen sulphide is effected in nature by specialised, strictly anaerobic bacterium of the genus Desulfotomaculum. These sulphate reducing bacteria (SRB) are heterotrophic organisms that utilise sulphate, thiosulphate, S2O3--, sulphite, SO3-- or other reducible sulphur-containing ions as terminal electron acceptors in their respiratory metabolism. In the process, these sulphur-containing ions are reduced to hydrogen sulphide.

Heterocysts are specialized nitrogen-fixing cells formed during nitrogen starvation by some filamentous cyanobacteria, such as Nostoc punctiforme, Cylindrospermum stagnale, and Anabaena sphaerica.

Bacillus species are aerobic, sporulating, rod-shaped bacteria that are ubiquitous in nature.

Methanogenesis or biomethanation is the formation of methane by microbes known as methanogens. Organisms capable of producing methane have been identified only from the domain Archaea, a group phylogenetically distinct from both eukaryotes and bacteria, although many live in close association with anaerobic bacteria.

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Nitrogen-fixing bacteria, such as Rhizobium, live in symbiotic relationships within the root nodules of leguminous plants, which include various pulses.