Plants are a very important part of our lives. They provide oxygen, wood, medicine and food, but they don’t do it alone.
Friendly bacteria and fungi help plants to grow by assisting them in obtaining nutrients such as phosphorous and nitrogen, or by defending the plants from pests.
With the help of bacteria and their DNA, scientists have also developed ways to artificially improve plants via a process called “genetic modification”.
Rhizobia (like Mesorhizobium ventifaucium LMG 29643T) are a group of nitrogen-fixing bacteria that form a symbiotic relationship with leguminous plants, such as beans, peas, and clover. This partnership has several positive effects on plant growth, which are essential for both the plant and the surrounding ecosystem:
- Nitrogen Fixation: Rhizobia have the remarkable ability to convert atmospheric nitrogen (N2) into ammonia (NH3) through a process called nitrogen fixation. Rhizobia provide plants with a direct source of fixed nitrogen, which is readily available for plant uptake. This can significantly enhance the plant's nitrogen supply, promoting lush and vigorous growth. Moreover, farmers can reduce their reliance on synthetic nitrogen fertilizers.
- Enhanced Plant Health: Rhizobia also stimulate plant growth through the production of growth-promoting substances like auxins. This can lead to healthier and more robust plants, better equipped to withstand environmental stressors such as drought and disease.
- Soil Improvement: The presence of rhizobia in the root nodules of leguminous plants can improve soil structure and nutrient content. The organic matter produced as a result of decaying root nodules contributes to soil fertility over time, benefiting other non-leguminous plants in the ecosystem.
Nostoc sp. (ULC 046)
Nitrogen (N) is an essential element for the growth and development of plants. Actually, crop yield depends on great inputs of N-based fertilizers, which are expensive and limited. Some prokaryotic microorganisms, such as cyanobacteria, perform N2 fixation, converting nitrogen gas from the atmosphere into ammonia, a nitrogen source that is assimilable for plants. Accordingly, cyanobacterial strains can be used as biofertilizers, as in rice cultivation, in association with the fern Azolla. By incorporating cyanobacteria into agricultural systems, other negative environmental impacts, such as water pollution and greenhouse gas emissions, can also be reduced.
Arbuscular mycorrhizal fungi
One of the major challenges of the 21st century is the sustainable production of food for an ever-growing population, which is expected to reach 9.7 billion people by 2050 (United Nations, 2019). Increases in yields of food production systems over the last two centuries have been heavily reliant on chemical pesticides and mineral fertilizers. However, these products are part of the world’s most energy-intensive production processes and are often dependent on finite resources such as phosphorus fertilizers. The extensive use of fertilizers in food production systems is a major factor contributing to agricultural global greenhouse gas emissions, and can have severe adverse effects on biodiversity and environmental sustainability. Other pressing issues include the development of pesticide resistance, the emergence of new crop pathogens, and increasing consumer demand for pesticide-free food. There is rapidly emerging interest to reduce our agricultural footprint and reliance on agrochemicals through the use of biostimulants, including microbial inoculants (Salomon et al., 2022).
Many microorganisms inhabiting the rhizosphere can be used as biofertilizers and biopesticides. Among these are the arbuscular mycorrhizal fungi which are beneficial for plant growth, nutrition and protection against stresses. These organisms live in association with above 72 % of plant species among which most if not all the important agricultural and horticultural crops. These organisms form an intricate network of hyphae within the roots and develops profusely in the soil extending the exploration zone of the root by up to 700 times. These tiny hyphae are able to take up nutrients such as phosphorus and nitrogen in the soil not accessible to the roots and transport them to their host, feeding the plant in exchange of carbon resources from the photosynthesis. These fungi thus improve plant vigor and yields and have significant potential to reduce the demand of agrochemicals. The development of microbial products with these root symbionts have gained importance because they have the potential to increase farm productivity and yield resilience for sustainable food production.
Genetically modified crops
Plasmids are small, circular DNA molecules that naturally occur in bacteria and yeasts. Artificial plasmids have become pivotal tools in biotechnology, and among their many applications, the development of genetically modified crops (GMOs) is probably the most notorious. Plasmids can be used to introduce new genes into plants, which can make crops more resistant to droughts and pests, increase crop yield per acre and improve the nutritional value and shelf life of the harvested food.
While in principle, genetic engineering is an improved form of traditional plant breeding, there are still concerns about the impact of foreign genes on consumer health and the environment, and about the consequences on the economic model of farming.