CC BY
0INTERNATIONAL SCIENTIFIC AND PRACTICAL CONFERENCE "STATUS AND DEVELOPMENT PROSPECTS OF FUNDAMENTAL AND APPLIED MICROBIOLOGY: THE VIEWPOINT OF YOUNG SCIENTISTS" _25-26 SEPTEMBER, 2024_
MICROBIAL MEDIATORS OF ECOSYSTEM FUNCTIONS: NITROGEN FIXATION, BIODEGRADATION, AND
BIOREMEDIATION
1Akanksha Bansal, 2Shahla Tanveer
1Research scholar, Department of Chemistry, St. John's College, Dr. Bhimrao Ambedkar
University, Agra, India.
2Assistant Professor, Department of Chemistry, Integral University, Lucknow, India. https://doi.org/10.5281/zenodo.13842141
Abstract. Microorganisms play a pivotal role in ecosystems by driving essential processes such as nitrogen fixation, biodegradation, and bioremediation. Nitrogen-fixing bacteria, such as Azotobacter and Rhizobium, transform atmospheric nitrogen into ammonia, which increases soil fertility and makes nitrogen available to plants. Plant growth and sustainable agriculture depend on this mechanism. Microorganisms like fungi and bacteria break down organic materials during the process of biodegradation, releasing nutrients back into the environment and dissolving contaminants like plastics and hydrocarbons. Furthermore, microbes play a crucial role in bioremediation, which involves cleaning up or detoxifying contaminants from the air, water, and soil to restore ecosystems that have been harmed by heavy metals, oil spills, and industrial waste. These microbialfunctions support pollution prevention, nutrient cycling, and ecosystem resilience, underscoring the significance of these processes in preserving the sustainability and health of the environment.
Keywords: microorganism, Nitrogen-fixing bacteria, Ecosystem, Agriculture.
INTRODUCTION
Microorganisms may be found anywhere, even in the most unfriendly settings. They are appealing agents for bioremediation because of their capacity to change almost any type of organic material, whether manufactured or natural. However, microbial activity needs certain conditions. Organic pollutants may not break down rapidly in a soil environment for a variety of reasons, including high concentrations of pollutants, a lack of electron acceptors, insufficient nutrient availability, and unfavorable environmental factors like moisture, temperature, pH, ionic strength, or redox status. The majority of organic matter is mineralized aerobically in nature, with oxygen serving as the ultimate electron acceptor. The degradation of organic materials is often the result of a series of steps carried out by several microbes working together or sequentially to bring about the mineralization of the material. The mineralization frequently follows the same pattern as xenobiotics. Slater, J. H. and Lovatt, D. (1984) showed that mixed communities of microorganisms may be more efficient at mineralizing some pollutants, such as chlorinated aromatic hydrocarbons and alkylbenzene sulfonates, than individual species. Sometimes pollutants cannot be directly assimilated by the microbes that oxidize them (co-metabolism) but may instead be further transformed by other populations. These commensal relationships can significantly enhance the mineralization of recalcitrant pollutants and prevent the accumulation of toxic intermediates [1, 2].
NITROGEN FIXATION BY MICROORGANISMS
N2 is the most abundant gas in Earth's atmosphere, it is extremely unreactive [3]. Biological nitrogen fixation is an important part of the microbial processes [4]. Biological nitrogen fixation
INTERNATIONAL SCIENTIFIC AND PRACTICAL CONFERENCE "STATUS AND DEVELOPMENT PROSPECTS OF FUNDAMENTAL AND APPLIED MICROBIOLOGY: THE VIEWPOINT OF YOUNG SCIENTISTS" _25-26 SEPTEMBER, 2024_
is carried out only by prokaryotes, which may be symbiotic or free living in nature. The process of biological nitrogen fixation, which is facilitated by nitrogenase enzymes, is widely known to be crucial for soil biological activity. The amount of nitrogenase present in the soil is determined by a variety of biological factors, including the ability of particular microbes and plant genotypes to fix nitrogen under different climatic circumstances. On the other hand, nitrogenase activity varies depending on the plant. Free-living, non-photosynthetic aerobic bacteria's ability to fix nitrogen is highly reliant on an abundance of organic C substrates, an oxygen-rich environment, and favorable moisture levels [5].
Nitrogen-fixing organisms are generally active in plant root zone soil. Plants that are capable of releasing exudates exhibit higher nitrogen fixation activity in soil [6]. Before it can be incorporated into biological molecules, N2 must be chemically reduced to the equivalent of ammonia. The biological reduction of nitrogen is catalyzed by a multimeric enzyme complex, nitrogenase [3], Nitrogenase consists of two conserved proteins: an iron (Fe) containing dinitrogenase reductase (or Fe protein), encoded by the nifH gene and a molybdenum iron (MoFe) dinitrogenase (or MoFe protein) that is encoded by the nifDK genes [5]. This enzyme is irreversibly inhibited by molecular oxygen and reactive oxygen species. Oxygen stress on diazotrophic (nitrogen-fixing) organisms triggers a wide range of protective responses aimed at deterring the inhibitory effects of oxygen on nitrogenase. The level of resistance to oxygen stress and the mechanisms involved vary among diazotrophs and influence niche selection. The evolutionary trajectory of adaptive mechanisms that protect nitrogenase from molecular oxygen and reactive oxygen species can be discerned in physiological patterns in microbial morphology, biochemistry, physiology, and community structure along a gradient from anaerobic to fully aerobic environments [3]. Nitrogen-fixing free-living microorganisms have frequently been reported as plant growth promoters [7].
ROLE OF BACTERIA IN MICROORGANISMS
Azotobacter: Even though it may thrive in environments with low O2 concentrations, Azotobacter is an obligate aerobe. This bacterium's ecological spread is a complex topic that depends on several variables that affect whether the organism is present in a particular soil or not [8]. One well-known example of what is known as associative nitrogen fixers is the genus Azospirillum of bacteria, which are found in the soils of tropical, subtropical, and temperate climates. These bacteria form intimate connections with the roots of a variety of cultivated and wild plants [9-10].
Rhizobium: Rhizobium is known for its ability to establish symbiotic interactions with leguminous plants by the formation and colonization of root nodules, where bacteria fix nitrogen to ammonia and make it available for the plant. The bacteria are mostly rhizospheric microorganisms, despite their ability to live in the soil for a long period [8].
MICROBIAL BIODEGRADATION AND BIOREMEDIATION
The term "microbial biodegradation" describes how microorganisms break down organic materials. By recycling nutrients and lowering pollution, microbes are essential to ecosystems. Enzymes are used by bacteria, fungi, and other microorganisms to convert complex organic materials such as hydrocarbons, polymers, and pesticides into simpler compounds like carbon dioxide and water. The capacity of bacteria, such as Pseudomonas, Bacillus, and Mycobacterium, to break down a wide range of substances via aerobic and anaerobic metabolic pathways makes them particularly important. Fungi are excellent at breaking down lignin and other persistent
INTERNATIONAL SCIENTIFIC AND PRACTICAL CONFERENCE "STATUS AND DEVELOPMENT PROSPECTS OF FUNDAMENTAL AND APPLIED MICROBIOLOGY: THE VIEWPOINT OF YOUNG SCIENTISTS" 25-26 SEPTEMBER, 2024
organic contaminants. White-rot species such as Phanerochaete chrysosporium are one example of this. Applications of biodegradation include sewage treatment, composting, and minimizing landfill trash, where bacteria assist reduce the build-up of hazardous organic compounds [12, 13, 14].
Figure 1. The three groups of nitrogen-fixing organisms include some main genera. In red: genera including symbiotic nitrogen-fixing species; in black: orders or genera (in italics) including free-living nitrogen-fixing species [11].
Microbial Bioremediation is the process of using microorganisms to detoxify and remove pollutants from contaminated environments. This natural and cost-effective method involves microbes metabolizing pollutants into less harmful compounds, making it an essential tool for environmental cleanup. There are two main approaches: in situ bioremediation, where the cleanup occurs at the contamination site, and ex-situ bioremediation, which involves the removal of contaminated material for treatment elsewhere. Specific techniques like bio venting (supplying oxygen to stimulate microbial activity), bioaugmentation (introducing specialized microbes), and phytoremediation (using plants in conjunction with microbes) are commonly applied. Microorganisms like Pseudomonas and Bacillus are known for their ability to immobilize or transform toxic heavy metals such as arsenic, lead, and mercury. Meanwhile, bacteria like Alcanivorax and fungi such as Aspergillus are effective at degrading hydrocarbons in oil spill cleanups. Notable case studies include the use of indigenous bacteria to accelerate oil breakdown after the Exxon Valdez oil spill in 1989 and the bioaugmentation efforts in the Ganges River to mitigate heavy metal contamination [16, 17, 18].
Figure 2. Scheme of Microbial biodegradation of organic pollutants [15]
INTERNATIONAL SCIENTIFIC AND PRACTICAL CONFERENCE "STATUS AND DEVELOPMENT PROSPECTS OF FUNDAMENTAL AND APPLIED MICROBIOLOGY: THE VIEWPOINT OF YOUNG SCIENTISTS" 25-26 SEPTEMBER, 2024
Figure 3. Microbial Bioremediation has been an efficient process for the removal of heavy metal contaminants. The figure shows various positive aspects and some drawbacks associated with this process over other physicochemical techniques [19]
CONCLUSION
Microorganisms play a crucial role in preserving ecological equilibrium by employing nitrogen fixation and biodegradation. Microbial technological advancements, such as bioremediation, provide long-term solutions for soil enrichment and pollution cleaning.
ACKNOWLEDGEMENTS
I express my deep sense of gratitude to my Ph.D. supervisor, Prof. Susan Verghese P., Department of Chemistry, St. John's College, Dr. Bhimrao Ambedkar University, Agra for suggesting the problem, valuable guidance, encouragement, and constant help during the study period.
REFERENCES
1. Slater, J. H.; Lovatt, D. (1984), In Degradation of Organic Compounds; Gibson, D. T., Ed.; Marcel Dekker: New York.
2. Bollag, J. M., Mertz, T., & Otjen, L. (1994). Role of microorganisms in soil bioremediation.
3. Frank, I.B., P. Lundgren and P. Falkowski, (2003). Nitrogen fixation and photosynthetic oxygen evolution in cyanobacteria. Research in Microbiol., 154: 157-164.
4. Simon, T., (2003). Utilization of biological nitrogen fixation for soil evaluation. Plant Soil Environ., 49: 359-363.
5. Matthew, C.J., M.K. Bjorkman, M.K. David, A.M. Saito and P.J. Zehr, (2008). Regional distributions of nitrogen-fixing bacteria in the Pacific Ocean. Limnol. Oceanogr, 53: 63-77
6. Egamberdieva, D. and Z. Kucharova, (2008). Cropping effects on microbial population and nitrogenase activity in saline arid soil. Turk. J. Biol., 32: 85-90.
7. Requena, N., T.M. Baca and R. Azcdn, (1997). Evolution of humic substances from unripe compost during incubation with lignolytic or cellulolytic microorganisms and effects on the lettuce growth promotion mediated by Azotobacter chroococcum. Biol Fertil Soils, 24: 59-65
8. Gonzalez, L.J., B. Rodelas, C. Pozo, V. Salmeron, M.V. Mart nez and V. Salmeron, (2005). Liberation of amino acids by heterotrophic nitrogen-fixing bacteria. Amino Acids, 28: 363367.
INTERNATIONAL SCIENTIFIC AND PRACTICAL CONFERENCE "STATUS AND DEVELOPMENT PROSPECTS OF FUNDAMENTAL AND APPLIED MICROBIOLOGY: THE VIEWPOINT OF YOUNG SCIENTISTS"
_25-26 SEPTEMBER, 2024_
9. Doroshenko, E.V., E.S. Boulygina, E.M. Spiridonova, T.P. Tourova and I.K. Kravchenko, (2007). Isolation and characterization of nitrogen-fixing bacteria of the genus Azospirillum from the Soil of a Sphagnum Peat Bog. Microbiol., 76: 93-101.10. Rawia, E.A., M.A. Nemat and H.A. Hamouda, (2009). Evaluate the effectiveness of bio and mineral fertilization on the growth parameters and marketable cut flowers of Matthiola incana L. American-Eurasian J. Agric. and Environ. Sci., 5: 509-518.
11. Soumare, A., Diedhiou, A. G., Thuita, M., Hafidi, M., Ouhdouch, Y., Gopalakrishnan, S., & Kouisni, L. (2020). Exploiting biological nitrogen fixation: a route towards a sustainable agriculture. Plants, 9(8), 1011.
12. Singh, S. N. (Ed.). (2011). Microbial degradation of xenobiotics. Springer Science & Business Media.
13. Van Hamme, J.D., et al. (2003). Microbial hydrocarbon degradation: Insights from the genomics era. Microbiology and Molecular Biology Reviews.
14. Pointing, S. (2001). Feasibility of bioremediation by white-rot fungi. Applied Microbiology and Biotechnology.
15. Singha, S., & Chatterjee, S. (2022). Soil pollution by industrial effluents, solid wastes and reclamation strategies by microorganisms. In Soil Health and Environmental Sustainability: Application of Geospatial Technology (pp. 471-488). Cham: Springer International Publishing.
16. Vidali, M. (2001). Bioremediation. An overview. Pure and Applied Chemistry.
17. Prince, R.C. (2005). The microbiology of marine oil spill bioremediation. Marine Pollution Bulletin.
18. Ghosh, M., and Singh, S.P. (2005). A review on phytoremediation of heavy metals and utilization of its byproducts. Applied Ecology and Environmental Research.
19. Zango Usman, U., Mukesh, Y., Vandana, S., Sharma, J. K., Sanjay, P., Sidhartha, D., & Sharma Anil, K. (2020). Microbial bioremediation of heavy metals: Emerging trends and recent advances. Research Journal of Biotechnology Vol, 75(10)
