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Life hidden in the soil: Why are denitrifying microorganisms the guardians of the environment?
In our daily lives, people who are worried about environmental pollution and ecological balance may not know that there are some tiny lives lurking in the soil. It is they who are exerting invisible power to protect the health of the earth. The name of these microorganisms is denitrifiers and they play a vital role in the nitrogen cycle.
Denitrification is a process facilitated by microorganisms that reduces nitrate (NO3−) to ultimately produce molecular nitrogen (N2). This process is mainly performed by facultative anaerobic bacteria, which reduce highly oxidized nitrogen compounds in an anoxic environment and use organic matter as a source of energy. Denitrifying microorganisms require extremely low oxygen concentrations, usually less than 10%, in order for the process to proceed smoothly.
The denitrification process not only provides energy for organisms that perform the reduction of nitrate to dinitrogen, but some anaerobic ciliates can also use denitrifying endosymbionts to obtain energy, similar to the way oxygen-breathing organisms use mitochondria.
In nature, the denitrification process is not only hidden in the soil, but also throughout the marine ecosystem. This process occurs mainly in an anoxic environment, where nitrate or nitrite can serve as the terminal electron acceptor instead of oxygen. This process is particularly important in environments such as wetlands, oil fields and some marine environments. In addition, denitrification can even occur in environments with more surface oxygen, showing its biological adaptability.
Many factors affect denitrification rate, such as temperature and pH. For example, in a bacterium called Pseudomonas mandelii, its denitrification gene expression decreased significantly when the temperature was below 30°C or the pH was below 5.
One of the most well-known applications of the denitrification process is nitrogen removal in water plants, which plays an important role in wastewater treatment. The denitrification process is effective in reducing groundwater contamination caused by excessive fertilizer use in industry and agriculture, and it can also reduce nitrogen leakage when creating wetlands and riparian areas.
Efficient wood chip bioreactors have been studied since the 2000s, showing their potential to remove nitrates from agricultural runoff and manure.
As we celebrate the changes these tiny creatures have made to the environment, we must also pay attention to the possible release of nitrous oxide (N2O) during the denitrification process. This gas is not only a greenhouse gas but also a depletor of the ozone layer. substance. Therefore, balancing the effects of the denitrification process and preventing its negative effects are issues that scientists need to pay attention to.
In the treatment of industrial wastewater, many denitrification bioreactors (such as membrane bioreactors) are commercially applied. These technologies are based on different electron donors and use these microorganisms for denitrification treatment. Not only biology, but also modern chemical methods such as reverse osmosis and ion exchange can effectively remove nitrates from water, but these methods also have their own shortcomings and challenges.
Taken together, denitrifying microorganisms play an indispensable role in maintaining ecological balance and promoting soil health. Are there more tiny beings living around us, and how do they affect the world in obscurity?
