Bacterial Bio-Fertilisers

Bacterial Bio-Fertilisers

	Bacterial Bio-Fertilisers Here, live cells of bacteria are used as fertilisers. They are the principal nitrogen fixers in the soil and may be either free-living or symbiotic (within the nodules of legume roots, leaf nodules of certain plants and stem nodules of Sesbania grandiflora). Some bacterial genera can solubilise phosphorus from the bound form (Bacillus, Pseudomonas sp.). There are certain other bacterial members which during their metabolic activity, make available certain essential trace elements like manganese, calcium and zinc in the soil for plant absorption. Some bacteria like Agrobacterium sp. and Pseudomonas fluorescence supply growth hormones like indole acetic acid to the plants.
Certain groups of bacteria like the Pseudomonas fluorescence living in association with the rhizosphere of most of crop plants (rhizobacteria promoting plant growth) supply all the essential nutrients required for the growth of the crop and in addition, protects the plant roots from the attack by soil-borne pathogens (saprophytic suppression). The nitrogen fixing ability of the bacteria can be studied under the following heads. Free-living nitrogen fixers Among the large number of free-living nitrogen fixers, only two have attracted the scientists, they are Azotobacter and Klebsiella. Azotobacter requires oxygen to flourish and Klebsiella and Rhodospirillum can survive both in the presence and absence of oxygen. Apart from fixing nitrogen, Azotobacter chroococcum has the ability to synthesise and secrete B-vitamins, growth hormones and antifungal antibiotics into its environment. Azotobacter has one drawback, its nitrogen fixing ability is regulated by the presence of nitrogenous compounds in its environment.
Thus it cannot be used along with a nitrogenous fertiliser. Klebsiella is another promising free-living nitrogen fixer, and it has been possible to isolate its 'nif' genes (17 of them) and to introduce them into E.coli. It is hoped that one day it will be possible to introduce these genes into non-nitrogen-fixing plants to make them self-sufficient in nitrogen.

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