Plants can survive without nitrogen-fixing bacteria, although they typically rely on these bacteria to convert atmospheric nitrogen into a usable form. Two common ways for plants to obtain nitrogen are through nitrogen fixation by symbiotic bacteria in the root nodules of legumes and through the uptake of nitrate and ammonium ions present in the soil. In the absence of nitrogen-fixing bacteria, plants may require additional nitrogen inputs, such as fertilizers, to ensure their optimal growth.

Dr Lassaad Hedhili thank you for your contribution to the discussion

Organisms are unable to grow in the absence of nitrogen fixation. Plants that are deficient in nitrogen appear pale or yellowish. They produce quite fewer flowers & fruits than other plants. The majority of plants will also not be able to directly consume nitrogen from the environment. Nitrogen gas makes up 78% of the air we breathe. Most nitrogen enters ecosystems via certain kinds of bacteria in soil and plant roots that convert nitrogen gas into ammonia (NH3). This process is called nitrogen fixation. A very small amount of nitrogen is fixed via lightning interacting with the air.Plants can take up two forms of nitrogen: nitrate (NO3-) and ammonium (NH4+). Although you can apply either organic or inorganic forms of nitrogen, plants will only take up these two forms. Once in the soil, all forms of nitrogen undergo chemical changes to ultimately transform into plant-available nitrogen. Plant and animal wastes decompose, adding nitrogen to the soil. Bacteria in the soil convert those forms of nitrogen into forms plants can use. Plants use the nitrogen in the soil to grow. People and animals eat the plants; then animal and plant residues return nitrogen to the soil again, completing the cycle. Nitrogen may be lost from the soil by leaching, denitrification and volatilization. Leaching is the movement of plant nutrients in the soil solution to a point below the root zone. Ammonium, which is held in an exchangeable form on soil particles, does not readily leach. Without it, they'd be unable to produce proteins, create enzymes or even photosynthesize. With nitrogen in such high demand, it's often one of the biggest limits on plant growth — there simply isn't enough of it to go around. The role of nitrogen-fixing bacteria is to provide plants with nutrients that they cannot acquire from the air. Nitrogen-fixing bacteria perform what crops cannot: they obtain assimilative N. Bacteria absorb it as a gas from the air and release it to the soil, typically as ammonia.