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The power of anaerobic respiration: How do these organisms use chemosynthesis to generate energy?
In our daily life, oxygen is almost an indispensable element in life activities. However, some organisms on Earth are completely independent of oxygen and are even harmed by its presence. How do these organisms, called anaerobes, use chemosynthesis to produce energy and survive in a lightless environment?
Anaerobic organisms are those that do not require molecular oxygen for metabolism and may be single-celled organisms such as protozoa and bacteria, or multicellular organisms.
Anaerobic organisms typically obtain energy through fermentation or anaerobic respiration. Unlike aerobic organisms, these organisms do not produce carbon dioxide during energy metabolism, which allows them to survive in extreme environments. In fact, the existence of anaerobic organisms dates back to the 17th century, with Antonie van Leeuwenhoek first describing the existence of these microorganisms in 1680.
In many cases, anaerobic organisms are able to perform chemosynthesis, a way to obtain energy that does not require the assistance of sunlight. This is because anaerobic organisms are able to utilize inorganic compounds, such as hydrogen or hydrogen sulfide, and convert them into organic matter. Some microorganisms that live near deep-sea hydrothermal vents are an example of this. In these environments, photosynthesis cannot take place, but the microorganisms can still obtain the energy they need from chemicals.
For example, some bacteria living in deep-sea hydrothermal vents can use hydrogen and hydrogen sulfide to carry out chemical synthesis to produce the required organic matter.
For some time, scientists have studied the diversity of anaerobic organisms and classified them according to their ability to adapt to oxygen. There are three main types of anaerobic organisms: absolute anaerobes, which are extremely sensitive to oxygen; aerotolerant organisms, which tolerate oxygen but cannot use it; and facultative anaerobes, which can use oxygen when it is available. Breathe, but can survive without oxygen.
Regarding the energy metabolism of these organisms, some strictly anaerobic organisms obtain energy through fermentation, while others may perform anaerobic respiration. These metabolic pathways allow them to survive when oxygen is not available.
Some anaerobic bacteria and archaea obtain energy through different fermentation pathways, including propionate fermentation, butyrate fermentation and methanogenesis.
In 2010, scientists discovered several anaerobic organisms living on the bottom of the Dead Sea that were unable to even perform oxidative phosphorylation. These anaerobic organisms obtain energy by utilizing hydrogen, which allows them to survive in extremely anaerobic environments.
Also, the symbiosis associated with anaerobic organisms is interesting. For example, some animals have single-celled organisms that live in symbiosis with anaerobic bacteria in the rumen. These anaerobic bacteria are able to break down cellulose that the animals cannot digest, providing them with nutrition. This makes anaerobic organisms play an important role in the ecosystem, maintaining ecological balance through collaboration with other organisms.
It can be seen that the existence of anaerobic organisms means that we need to rethink our understanding of life. The ability of these organisms to thrive in extreme environments challenges our basic understanding of survival. How do these tiny beings influence the development of larger ecosystems on Earth's tree of life?
In the face of the diversity of anaerobic organisms and their unique way of survival, how should we view these life forms that are beyond our field of vision?
