Bacteria that reduces fertilser use

Sunday 15 February 2004

indian scientists have discovered a novel microorganism in salty marshlands, which has the potential to absorb nitrogen -- an essential plant nutrient -- from the atmosphere and make it available to crops. In addition, the microbe can help plants extract phosphorus from the soil

-- indian scientists have discovered a novel microorganism in salty marshlands, which has the potential to absorb nitrogen -- an essential plant nutrient -- from the atmosphere and make it available to crops. In addition, the microbe can help plants extract phosphorus from the soil. Scientists from Chennai-based M S Swaminathan Research Foundation (mssrf), who have discovered the microbe, claim it can considerably cut down the use of chemical fertilisers.

Nitrogen is an essential building block of life on Earth. It is a fundamental component of the nucleic acids that determine the genetic character of all living organisms as well as the enzymes that drive the tiny metabolic machinery of every living cell. Plants too require nitrogen to survive. Although more than three-fourth of the Earth's atmosphere is full of nitrogen, the plants can take up only a paltry amount of it. This is because nitrogen molecules exist in pairs of two atoms and the bonding between them is so strong that they are not available for most chemical reactions (read: they cannot be readily absorbed by plants).

However, there are many known microorganisms such as rhizobium bacteria, which reside on the roots of leguminous crops (such as peas and beans) and supply a large amount of nitrogen to the plants, after absorbing it from the atmosphere. Non-leguminous crops, however, are not blessed with such an endowment. As a result, all major crops depend mainly on chemical fertilisers for their nitrogen/phosphorus/potassium/sulphur requirements.

mssrf scientist, P Loganathan, says the new microbe can function as rhizobium-like microorganisms for all crops. Moreover, the bacterium can also dissolve phosphate compounds, which otherwise remain locked up inside soil. These properties of the microbe, they feel, are good enough reasons to promote it as a biofertiliser. The bacterium has more worth -- during experiments, its inoculation helped a rice variety (panni), which is widely used in south India, to grow in saline soil. "This is a significant development, considering that 10-15 per cent of arable land in the country is plagued by salinity," says R P Gupta, head of the department of microbiology at the Ludhiana-based Punjab Agricultural University.

The bacterium, named Swaminathania salitolerans, was isolated from Porteresia coarctata -- a wild variety of rice. It was found in the Pichavaram mangrove forest, situated along the Tamil Nadu coast. The microbe has never been reported earlier; it belongs to the Acetobacteraceae family of microbes. Its strains were found to have beneficial effects during trials conducted in a greenhouse. Plants treated with the bacterial culture (in a sodium chloride base) showed increased levels of nitrogen and phosphorus, corroborating the claim of the mssrf scientists. The next step, they say, is to conduct field trials to scientifically establish the potential of S salitolerans. "This work will pave way for understanding and tapping the rich microbial biodiversity that exists in the country," says M S Swaminathan, head of mssrf and a noted agricultural scientist.

But according to B D Kaushik, head of the department of microbiology at the New Delhi-based Indian Agricultural Research Institute, it is too early to make sweeping claims about the potential of the microbe. "A number of microbes exhibit nitrogen-fixation properties. All of them tap nitrogen to meet their metabolic requirements, but most do not have excess of the element to be given to soil or the plants," he explains.

If its worth is proven, S salitolerans would be a boon for India -- rice, the crop on which the mssrf scientists are currently testing the bacterial system, accounts for a sizeable portion of nitrogenous fertilisers used in the country. As per estimates, rice and wheat corner about 70 per cent of the more than 13 million tonnes of nitrogenous fertilisers used in the country. The bacterium can be used in the fields of most crops. "The finding has enormous implications. But there is a long way to go before the microbe can become a constitute of the integrated plant management," says Palaniappan, chief technology officer of the Tutucurin-based spic Centre for Research and Development.

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