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The Miracle of the Deep Sea: How do green sulfur bacteria find energy on the seafloor 2,500 meters deep?
In the depths of the vast ocean, there are some mysterious and unique organisms living. Among them, green sulfur bacteria (Chlorobiota) have become a hot spot for scientists to study due to their special growth form and ecological role. These photosynthetic and autotrophic anaerobic organisms can not only survive in an oxygen-deficient environment, but can also use compounds of elemental sulfur as energy and carbon sources, showing amazing adaptability.
Green sulfur bacteria mainly live hundreds of meters underwater and use hydrogen sulfide as an electron donor, which makes them self-sufficient during photosynthesis and able to survive in low-light environments.
Characteristics of green sulfur bacteria
Green sulfur bacteria are Gram-negative and mostly rod-shaped or spherical in shape. These bacteria possess bubble sacs that allow them to float in water and use their photosynthetic pigments to capture light energy. The main photosynthetic pigments are bacteriochlorophyll c or d. These pigments are located in their unique photopolymers (chlorosomes) and can effectively capture light energy under extremely low light conditions.
Habitat
Most of these bacteria are mesophytic, prefer mild water temperatures, and mostly live in sediments at the bottom of water bodies. They require an anaerobic (anaerobic) environment and can photosynthesize in low light environments. In a surprising discovery, at a depth of about 100 meters in the Black Sea, scientists found large populations of green sulfur bacteria that survive with almost no light.
In the Pacific Ocean 2,500 meters deep from the surface, scientists discovered a type of green sulfur bacteria called GSB1. These bacteria rely on the low light of thermal vents to survive and do not rely on sunlight at all.
Photosynthesis and metabolism
Green sulfur bacteria use a photosynthetic process similar to that of plants, but their electron donors are primarily derived from inorganic sulfides. The reverse tricarboxylic acid cycle they use effectively uses carbon dioxide as the only source of carbon to synthesize the organic materials needed by cells. This allows them to continue to survive and reproduce even in waters with extremely low light.
When these bacteria perform photosynthesis, they usually oxidize sulfide to total sulfur to form sulfur beads, which is where their name comes from.
Relationship with other living things
Green sulfur bacteria often play an important role in the ecosystem of coral reefs, and in fact on Taiwan's coral reefs, these bacteria form the characteristic green layer. Not only do they provide nutrients to corals, they may also help detoxify them, making them integral to the entire ecosystem.
Future research directions
Because green sulfur bacteria play an important role in ecosystems in Earth's deep oceans, future research will provide a deeper understanding of their metabolic processes and the unique way they absorb and convert energy. This will be of great significance for exploring the diversity of life and its survival strategies in extreme environments.
The existence of green sulfur bacteria not only reveals more possibilities for life, but also inspires us to think deeply about the origin of life and its evolution. Is it possible that we can find such life forms that can survive in extreme environments on other planets?
