Purple Sulfur Bacteria—The First Alien Lifeform Discovered?

Bacteria - the absolute overlord of time

In an episode of the National Geographic program called "Super Germs", senior researcher Gray from Australia gave the children a wonderful geological biology lesson. She used the tip of her nose as the starting point of the formation of the earth (about 4.6 billion years ago), and then moved her finger along the shoulder to the right. When she reached the shoulder joint, she said: "At this point in time (more than 3 billion years ago), the earliest life forms, bacteria, appeared."

Then, she continued to move her fingers along the arm toward the fingertips. When she reached the wrist, she said, "For a long time when the arm length ratio was the same, there were only microorganisms on the earth. But at this point, plants and fish appeared on the earth." When her fingers reached between the first and second knuckles, she smiled and introduced to the students, "Now it's time for dinosaurs to appear."

Finally, she gave another brilliant example: "Where are we humans? We are at the tips of our fingers. If I give you a nail file, you can just file it lightly and the human beings will be gone."

Purple bacteria

Since the earliest life on Earth was bacteria, which one was it? Currently, scientists believe that the main organisms at that time (more than 3 billion years ago) should be a type of purple bacteria (Purple bacterium). This type of bacteria has special spectral characteristics and is distributed in the primitive ocean and on land.

Purple bacterium

Purple bacteria are actually mainly a type of anaerobic bacteria that can photosynthesize. They contain carotenoids, as well as pigments such as bacteriochlorophyll a and b, which can show red, purple, yellow, brown and other colors. Most of their photosynthesis occurs on the cell membrane. When the reaction center begins photosynthesis, the cell membrane will invaginate, forming a tube, sac, or flat layer.

Purple bacteria do not generate oxygen, which is the same as other bacteriochlorophyll-containing bacteria. Purple bacteria come in various shapes and sizes, and the most typical representative is the purple sulfur bacteria that can grow using thiosulfate and hydrogen sulfide.

In addition to the above types, there are some special purple bacteria that are slightly different. Among them, purple sulfur-free bacteria are their representatives. They can survive in an aerobic, dark organic nutrition environment, and the main organic matter they use is fatty acids and lactic acid, which is similar to general heterotrophic bacteria.

Purple non sulfur bacteria

Interestingly, although all of the above bacteria are collectively referred to as purple bacteria, microbiologists have found that they are not homologous, but have their own species and groups with different relationships.

Exploring space with purple bacteria

Now that we have a clear idea of ​​what is happening on our planet, can we use this information to do something? The answer is yes, and scientists have already put it into practice. By analyzing and simulating the distribution of purple bacteria on Earth, they built a spectral analysis model supported by big data and used it to search for life outside the solar system. In short, if people discover a planet with similar spectral characteristics when observing space in the future, it means that there may be life on it similar to microorganisms on Earth.

Judging from the current search results, Earth is still the only planet with life. However, the universe is so vast that there are countless Earth-like planets in the Milky Way alone, not to mention that the Milky Way is just one of many galaxies. The difficulty and challenge of the search are obvious, but the second Earth will be discovered sooner or later. Under this premise, whether life exists and, if so, at what stage of evolution has become a fascinating scientific question.

What is exciting is that a group of scientists from the Institute of Astrophysics in the Canary Islands have discovered an Earth-like planet through multiple deductions and searches for extrasolar life. The planet is located in a celestial system that also has a star similar to the sun, and its location happens to be in the life-friendly zone around the star, so it is possible that this planet could give birth to life! Since the spectral model used is based on the simulation of the distribution of purple bacteria, the first extraterrestrial life discovered by people is very likely to be a purple microorganism.

Similar "color life discovery theories" continue to ferment in the scientific community, and researchers from other disciplines continue to join in. For example, as early as 2011, scientists simulated the reflectance spectrum of green plants and built a corresponding analysis model to search for life planets. Following the same pattern, they believed that the first extraterrestrial life to be discovered should be a green plant that can photosynthesize.

The progress of science always starts with hypotheses and conjectures, which carry the wisdom and greatness of mankind and are also the marks and symbols of the continuous extension of civilization. Let your thoughts fly, and you will reap the entire blue sky.

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