Cyanobacteria are used as biofertilisers ,why?

Fix atmospheric nitrogen.

Cyanobacteria are used as biofertilizers primarily because they have the ability to fix atmospheric nitrogen.

One of the unique characteristics of cyanobacteria is their capability to perform nitrogen fixation. Nitrogen fixation is the process of converting atmospheric nitrogen gas (N2) into a biologically usable form, such as ammonia (NH3) or nitrate (NO3-). This process is important because nitrogen is an essential nutrient for plant growth, and many plants require it in a form they can readily absorb.

Cyanobacteria have specialized structures called heterocysts that enable them to carry out nitrogen fixation. These cells create an anaerobic environment, which is necessary for the activity of the nitrogenase enzyme responsible for nitrogen fixation. By fixing atmospheric nitrogen, cyanobacteria contribute to increasing the nitrogen content in the soil, making it available for plants to utilize.

As a result, when used as biofertilizers, cyanobacteria can enhance soil fertility and improve plant growth by providing a source of biologically fixed nitrogen. This reduces the reliance on synthetic nitrogen fertilizers, which can have negative environmental impacts when used excessively.

Regarding the other options provided:

• Cyanobacteria do produce mucilage, which is a slimy substance that helps them adhere to surfaces and form colonies. However, mucilage production is not the primary reason why cyanobacteria are used as biofertilizers.
• Cyanobacteria are actually autotrophic organisms, not heterotrophic. They can perform photosynthesis to produce their own energy using sunlight.
• While cyanobacteria are known for their ability to tolerate diverse environmental conditions and can grow in various habitats, this trait alone is not the main reason why they are used as biofertilizers. Their nitrogen-fixing ability is the primary characteristic that makes them valuable for this purpose.

Therefore, the correct reason why cyanobacteria are used as biofertilizers is their capability to fix atmospheric nitrogen.