Trichoderma

Trichoderma is a genus of fungi widely recognized for its significance in agriculture, biotechnology, and environmental sustainability. These fungi are commonly found in soil and plant roots, where they act as biological control agents by suppressing plant pathogens through competition for space and nutrients. Trichoderma species produce enzymes such as cellulases and chitinases that break down the cell walls of pathogenic fungi, thereby inhibiting their growth. These fungi can also induce systemic resistance in plants, strengthening their defense mechanisms against harmful external conditions.

In addition, Trichoderma maintains soil fertility by participating in nutrient cycling and the decomposition of organic matter, contributing to the formation of humus and structured soil. They are highly effective at breaking down cellulose, particularly in environments where other microorganisms may be less active. Their adaptability, non-pathogenic nature, and environmental benefits make Trichoderma an essential tool for sustainable agriculture.

Т. harzianum is particularly beneficial against a wide range of soil-borne pathogens and can colonize plant roots, enhancing nutrient availability and plant vitality. Meanwhile, T. viride excels in decomposing organic material and is widely used in composting and seed treatment for disease prevention.

References:

Druzhinina, I. S., Seidl-Seiboth, V., Herrera-Estrella, A., Horwitz, B. A., Kenerley, C. M., Monte, E., Mukherjee, P. K., Zeilinger, S., Grigoriev, I. V., & Kubicek, C. P. (2011). Trichoderma: The genomics of opportunistic success. Nature Reviews Microbiology, 9(10), 749–759. https://doi.org/10.1038/nrmicro2637

Harman, G. E., Howell, C. R., Viterbo, A., Chet, I., & Lorito, M. (2004). Trichoderma species—Opportunistic, avirulent plant symbionts. Nature Reviews. Microbiology, 2(1), 43–56. https://doi.org/10.1038/nrmicro797

Islam, S. M. S., Hossain, A., Hasan, M., Itoh, K., & Tuteja, N. (2023). Application of Trichoderma spp. As biostimulants to improve soil fertility for enhancing crop yield in wheat and other crops. In S. S. Gill, N. Tuteja, N. A. Khan, & R. Gill (Eds.), Biostimulants in Alleviation of Metal Toxicity in Plants (pp. 177–206). Academic Press. https://doi.org/10.1016/B978-0-323-99600-6.00014-1

Shoresh, M., Harman, G. E., & Mastouri, F. (2010). Induced systemic resistance and plant responses to fungal biocontrol agents. Annual Review of Phytopathology, 48, 21–43. https://doi.org/10.1146/annurev-phyto-073009-114450

Tyśkiewicz, R., Nowak, A., Ozimek, E., & Jaroszuk-Ściseł, J. (2022). Trichoderma: The Current Status of Its Application in Agriculture for the Biocontrol of Fungal Phytopathogens and Stimulation of Plant Growth. International Journal of Molecular Sciences, 23(4), Article 4. https://doi.org/10.3390/ijms23042329

Bacillus

Bacteria of the Bacillus genus are widely used in agriculture due to their positive effects on plant growth, soil health, and pest control. Certain Bacillus strains, including B. subtilis, can enhance the fixation of atmospheric nitrogen in the soil, converting it into a form that plants can absorb. Additionally, these strains can solubilize insoluble phosphate compounds in the soil, making phosphorus available to plants. Since both nitrogen and phosphorus are critical elements for plant growth, the use of Bacillus, especially B. subtilis, allows for a significant reduction in or even elimination of synthetic fertilizers.

Bacillus bacteria also promote plant growth by producing hormones such as auxins and cytokinins, stimulating root development and improving overall plant health. Furthermore, they enhance nutrient uptake efficiency in plants, resulting in higher yields. In addition, Bacillus can suppress the activity of various plant pathogens by producing antifungal and antibacterial substances and inducing systemic resistance in plants, thereby strengthening natural defense mechanisms against diseases.

Bacillus thuringiensis, particularly its specific strains, is known for producing proteins that are toxic to harmful insect larvae but harmless to beneficial insects like bees and other pollinators. This makes B. thuringiensis an effective and environmentally friendly bioinsecticide. Meanwhile, B. subtilis boosts plant immune responses by producing antimicrobial compounds and stimulating plant defense mechanisms, while also increasing nutrient availability by converting complex compounds into forms that plants can easily absorb.

In addition, Bacillus bacteria improve soil structure and aeration, creating a more favorable environment for plant growth. Some strains are also used in bioremediation, as they can degrade organic pollutants. Bacillus can also delay the spoilage of fruits and vegetables, extending their shelf life by inhibiting microorganisms responsible for decay.

Thus, Bacillus bacteria are versatile and effective allies in sustainable agriculture, promoting plant health and productivity while reducing harmful environmental impacts.

References:

Dame, Z. T., Rahman, M., & Islam, T. (2021). Bacilli as sources of agrobiotechnology: Recent advances and future directions. Green Chemistry Letters and Reviews, 14(2), 246–271. https://doi.org/10.1080/17518253.2021.1905080

Hashem, A., Tabassum, B., & Fathi Abd_Allah, E. (2019). Bacillus subtilis: A plant-growth promoting rhizobacterium that also impacts biotic stress. Saudi Journal of Biological Sciences, 26(6), 1291–1297. https://doi.org/10.1016/j.sjbs.2019.05.004

Khan, A. R., Mustafa, A., Hyder, S., Valipour, M., Rizvi, Z. F., Gondal, A. S., Yousuf, Z., Iqbal, R., & Daraz, U. (2022). Bacillus spp. as Bioagents: Uses and Application for Sustainable Agriculture. Biology, 11(12), 1763. https://doi.org/10.3390/biology11121763

Radhakrishnan, R., Hashem, A., & Abd_Allah, E. F. (2017). Bacillus: A Biological Tool for Crop Improvement through Bio-Molecular Changes in Adverse Environments. Frontiers in Physiology, 8, 667. https://doi.org/10.3389/fphys.2017.00667

Singh, S., & Shyu, D. J. H. (2024). Perspective on utilization of Bacillus species as plant probiotics for different crops in adverse conditions. AIMS Microbiology, 10(1), 220–238. https://doi.org/10.3934/microbiol.2024011

Azotobacter

Azotobacter is a free-living, nitrogen-fixing bacterium that plays a significant role in agriculture and is often used as a biofertilizer due to its ability to enhance soil fertility and improve crop yields.

Species of Azotobacter, particularly A. chroococcum, are renowned for their capacity to fix atmospheric nitrogen, converting it into a form readily available to plants. This process is especially important for crops that cannot form root nodules. Research indicates that using Azotobacter can boost crop yields, with potential increases reaching up to 45%, depending on the crop type.

Beyond nitrogen fixation, Azotobacter synthesizes plant hormones, including gibberellins and auxins, which promote root development, enhance plant growth, and improve nutrient uptake. Additionally, Azotobacter produces antimicrobial compounds that help protect plants from pathogens, thereby reducing disease risk.

Azotobacter also facilitates the solubilization of phosphorus and other essential nutrients in the soil, improving soil health and supporting sustainable farming practices by reducing the need for chemical fertilizers. Studies have shown that treating soil with Azotobacter can accelerate the decomposition of organic matter, such as in composting processes, thereby enhancing soil structure and nutrient cycling.

The use of Azotobacter contributes to reducing soil degradation and water pollution. Employing Azotobacter-based biofertilizers can save farmers between 60 – 80 kg of urea per hectare, offering both economic and environmental benefits.

References:

Aasfar, A., Bargaz, A., Yaakoubi, K., Hilali, A., Bennis, I., Zeroual, Y., & Meftah Kadmiri, I. (2021). Nitrogen Fixing Azotobacter Species as Potential Soil Biological Enhancers for Crop Nutrition and Yield Stability. Frontiers in Microbiology, 12. https://doi.org/10.3389/fmicb.2021.628379

Wani, S., Chand, S., & Ali, T. (2013). Potential Use of Azotobacter chroococcum in Crop Production: An Overview. Current Agriculture Research Journal, 1, 35–38. https://doi.org/10.12944/CARJ.1.1.04

Polyangium

Polyangium bacteria are primarily used in agriculture due to their ability to produce bioactive compounds that promote plant growth and protect against plant pathogens.

Certain Polyangium species, particularly Polyangium cellulosum, are capable of processing insoluble organic compounds, including cellulose. This capability enables Polyangium not only to degrade complex organic substances but also to synthesize compounds that inhibit the growth of harmful microorganisms.

Polyangium produces a variety of secondary metabolites with strong antibacterial and antifungal properties. By breaking down organic material, these bacteria enhance nutrient cycling in the soil, thereby improving soil health. Additionally, the metabolic processes of Polyangium improve both soil structure and fertility, making it a valuable asset in sustainable agriculture.

References:

Bhat, M. A., Mishra, A. K., Bhat, M. A., Banday, M. I., Bashir, O., Rather, I. A., Rahman, S., Shah, A. A., & Jan, A. T. (2021). Myxobacteria as a Source of New Bioactive Compounds: A Perspective Study. Pharmaceutics, 13(8), 1265. https://doi.org/10.3390/pharmaceutics13081265

Wang, J., ran, Q., Du, X., Wu, S., Wang, J., Sheng, D., Chen, Q., Du, Z., & Li, Y. (2021). Two new Polyangium species, P. aurulentum sp. Nov. And P. jinanense sp. Nov., isolated from a soil sample. Systematic and Applied Microbiology, 44(6), 126274. https://doi.org/10.1016/j.syapm.2021.126274

Pseudomonas

Bacteria of the Pseudomonas genus are widely known for their diversity and beneficial impact on soil health and plant growth. They are a natural component of soil microorganisms and are often used in agriculture as biological agents to improve crop yields and reduce the spread of plant diseases.

One of the main benefits of plant root systems’ growth by Pseudomonas bacteria is their ability to produce biologically active compounds, such as siderophores, which bind iron and make it more accessible to plants. They also release phytohormones that stimulate both the growth of plant root systems and overall plant elongation and flowering. Additionally, Pseudomonas bacteria secrete enzymes and antibiotics that inhibit the development of pathogenic microorganisms. These properties make Pseudomonas an effective tool in integrated plant protection strategies.

In addition to promoting plant growth, Pseudomonas bacteria help improve soil structure and microbiological balance. They are particularly useful in sustainable and organic agriculture, where there is a strong focus on natural resources and environmentally friendly solutions. With the help of these bacteria, it is possible to reduce the use of synthetic fertilizers and pesticides while maintaining high productivity.

Pseudomonas bacteria play a crucial role in advancing sustainable agriculture. Their ability to enhance plant and soil health makes them an indispensable resource for both traditional and modern agricultural practices.

References:

Mehmood, N., Saeed, M., Zafarullah, S., Hyder, S., Rizvi, Z. F., Gondal, A. S., Jamil, N., Iqbal, R., Ali, B., Ercisli, S., & Kupe, M. (2023). Multifaceted Impacts of Plant-Beneficial Pseudomonas spp. In Managing Various Plant Diseases and Crop Yield Improvement. ACS Omega, 8(25), 22296–22315. https://doi.org/10.1021/acsomega.3c00870

Misra, P., Archana, Uniyal, S., & Srivastava, A. K. (2022). Pseudomonas for sustainable agricultural ecosystem. In R. Pratap Singh, G. Manchanda, K. Bhattacharjee, & H. Panosyan (Eds.), Microbial Syntrophy-Mediated Eco-enterprising (pp. 209–223). Academic Press. https://doi.org/10.1016/B978-0-323-99900-7.00012-2

Nerek, E., Sokołowska, B., Nerek, E., & Sokołowska, B. (2022). Pseudomonas spp. In biological plant protection and growth promotion. AIMS Environmental Science, 9(4), Article Environ-09-04-029. https://doi.org/10.3934/environsci.2022029

Sah, S., Krishnani, S., & Singh, R. (2021). Pseudomonas mediated nutritional and growth promotional activities for sustainable food security. Current Research in Microbial Sciences, 2, 100084. https://doi.org/10.1016/j.crmicr.2021.100084

Sanow, S., Kuang, W., Schaaf, G., Huesgen, P., Schurr, U., Roessner, U., Watt, M., & Arsova, B. (2023). Molecular Mechanisms of Pseudomonas-Assisted Plant Nitrogen Uptake: Opportunities for Modern Agriculture. Molecular Plant-Microbe Interactions®, 36(9), 536–548. https://doi.org/10.1094/MPMI-10-22-0223-CR

Zboralski, A., & Filion, M. (2023). Pseudomonas spp. Can help plants face climate change. Frontiers in Microbiology, 14. https://doi.org/10.3389/fmicb.2023.1198131

Streptomyces

Streptomyces is a genus of bacteria that plays a significant role in agriculture due to its biocontrol and plant growth-promoting properties. These bacteria are widely found in soil and are known for their ability to produce various biologically active compounds, including antibiotics and enzymes, which positively impact crop health and productivity.

Streptomyces species are effective biocontrol agents against various plant pathogens. They produce secondary metabolites with antimicrobial properties that help suppress fungal and bacterial diseases in plants. For example, certain Streptomyces strains combat pathogens like Fusarium, which causes Fusarium head blight, significantly improving the growth of affected crops. Additionally, Streptomyces release volatile organic compounds that inhibit pathogen growth and promote plant health by strengthening their competitiveness in the root zone.

Streptomyces is well-known for its ability to produce antibiotics, which are used in both medicine and agriculture to control plant diseases. These bacteria also produce siderophores that bind iron from the environment, making it unavailable to pathogens while enhancing plant nutrient uptake. By breaking down complex organic compounds through enzymatic activity, Streptomyces improves soil health and provides plants with more accessible nutrients.

Beyond biocontrol, Streptomyces supports plant growth by producing phytohormones such as indole-3-acetic acid (IAA), which promotes root development and overall plant growth. These bacteria can solubilize essential nutrients like phosphorus, making them more accessible to plants. Moreover, by degrading organic matter and enhancing the activity of microbial communities, Streptomyces contributes to maintaining a healthy soil ecosystem.

References:

Khan, S., Srivastava, S., Karnwal, A., & Malik, T. (2023). Streptomyces as a promising biological control agents for plant pathogens. Frontiers in Microbiology, 14. https://doi.org/10.3389/fmicb.2023.1285543

Olanrewaju, O. S., & Babalola, O. O. (2019). Streptomyces: Implications and interactions in plant growth promotion. Applied Microbiology and Biotechnology, 103(3), 1179–1188. https://doi.org/10.1007/s00253-018-09577-y

Pacios-Michelena, S., Aguilar González, C. N., Alvarez-Perez, O. B., Rodriguez-Herrera, R., Chávez-González, M., Arredondo Valdés, R., Ascacio Valdés, J. A., Govea Salas, M., & Ilyina, A. (2021). Application of Streptomyces Antimicrobial Compounds for the Control of Phytopathogens. Frontiers in Sustainable Food Systems, 5. https://doi.org/10.3389/fsufs.2021.696518

Vurukonda, S. S. K. P., Giovanardi, D., & Stefani, E. (2018). Plant Growth Promoting and Biocontrol Activity of Streptomyces spp. As Endophytes. International Journal of Molecular Sciences, 19(4), 952. https://doi.org/10.3390/ijms19040952

Ensifer meliloti

Ensifer meliloti is a symbiotic bacterium that fixes nitrogen by forming nodules on the roots of legumes, particularly alfalfa (Medicago sativa), clover (Trifolium spp.), and other legumes. Nitrogen is fixed and converted into a plant-available form—ammonium. In this symbiotic relationship, plants provide the bacteria with energy in the form of organic compounds, while the bacteria supply the plants with essential nitrogen.

Beyond its symbiotic interactions, the bacterium enriches the surrounding soil with nitrogen, making it more accessible to other plants and helping to improve the soil's microbiological balance. This process enhances soil fertility, promotes crop growth, and reduces the need for synthetic nitrogen fertilizers.

In addition to nitrogen fixation, Ensifer meliloti produces phytohormones that stimulate root system development and enhance the plant's ability to absorb other nutrients. It can adapt to various soil conditions and effectively establish symbiosis with a wide range of legume species.

References:

Alami, S., Bennis, M., Lamin, H., Kaddouri, K., Bouhnik, O., Lamrabet, M., Chaddad, Z., Bacem, M., Abdelmoumen, H., Bedmar, E., & Missbah El Idrissi, M. (2023). The inoculation with Ensifer meliloti sv. Rigiduloides improves considerably the growth of Robinia pseudoacacia under lead-stress. Plant and Soil, 497, 1–19. https://doi.org/10.1007/s11104-023-05974-z

Biondi, E. G., Tatti, E., Comparini, D., Giuntini, E., Mocali, S., Giovannetti, L., Bazzicalupo, M., Mengoni, A., & Viti, C. (2009). Metabolic Capacity of Sinorhizobium (Ensifer) meliloti Strains as Determined by Phenotype MicroArray Analysis. Applied and Environmental Microbiology, 75(16), 5396–5404. https://doi.org/10.1128/AEM.00196-09

Rhizobium

Rhizobium bacteria are well-known for their crucial role in nitrogen fixation and promoting plant fertility. These bacteria can associate with various legumes, forming nodules on the plant's roots, resulting in mutually beneficial, symbiotic relationships. The plant provides the bacteria with carbohydrates and protection, while the bacteria fix atmospheric nitrogen, converting it into a form the plant can absorb. The nitrogen not utilized by the plant is released into the soil, where it becomes available for other plants. Rhizobium bacteria can fix 150–275 kg of nitrogen per hectare per season.

Not all Rhizobium bacteria can form symbiosis with all types of legumes. These relationships are species-specific – certain legume crops will form nodules with specific bacteria. For example, Rhizobium leguminosarum forms symbiosis with peas, vetches, and fava beans, Rhizobium trifolii - with clover, Rhizobium (Bradyrhizobium) - with soybeans, Rhizobium phaesoli - with beans, Rhizobium (Bradyrhizobium) lupini - with lupines, serradella, and sainfoin, Rhizobium galegae - with goat’s rue (Galega) and Rhizobium (Ensifer) meliloti forms symbiotic relationships with alfalfa, fenugreek, and sweet clover.

References:

Graham, P. H., & Vance, C. P. (2000). Nitrogen fixation in perspective: An overview of research and extension needs. Field Crops Research, 65(2), 93–106. https://doi.org/10.1016/S0378-4290(99)00080-5

Masson-Boivin, C., Giraud, E., Perret, X., & Batut, J. (2009). Establishing nitrogen-fixing symbiosis with legumes: How many rhizobium recipes? Trends in Microbiology, 17(10), 458–466. https://doi.org/10.1016/j.tim.2009.07.004

Peoples, M. B., Herridge, D. F., & Ladha, J. K. (1995). Biological nitrogen fixation: An efficient source of nitrogen for sustainable agricultural production? Plant and Soil, 174(1), 3–28. https://doi.org/10.1007/BF00032239

Somasegaran, P., & Hoben, H. J. (1994). Handbook for Rhizobia. Springer. https://doi.org/10.1007/978-1-4613-8375-8

Zahran, H. H. (1999). Rhizobium-Legume Symbiosis and Nitrogen Fixation under Severe Conditions and in an Arid Climate. Microbiology and Molecular Biology Reviews, 63(4), 968–989.