(ORDO NEWS) — Living on the walls of caves, HS-3 bacteria form structures from many different types of cells that appear at different stages of the colony’s existence. We can say that these microbes are at the first steps in the development of true multicellularity.
The development of multicellularity has become one of the key events in the evolution of life on Earth. It has led to the emergence of complex animals and plants with cells adapted to perform various functions.
Some prokaryotes are also capable of forming primitive structures from many cells, although they cannot be called truly multicellular.
The new cave bacteria that Japanese biologists have discovered are somewhere in the middle, combining cells of different types.
Kouhei Mizuno and his colleagues at the National Institute of Technology are studying extremophiles, bacteria that live in the most unfavorable conditions.
In particular, they studied the microbial population of the caves of Kyushu Island in southern Japan. Here they isolated HS-3 bacteria, which they managed to grow in the laboratory.
Watching the growth process, the researchers noticed something extremely unusual for prokaryotes. “I felt like I met an alien life form from a science fiction movie,” said Kohei Mizuno.
Instead of separating after division, the HS-3 cells were held together to form very long filaments. These threads were laid on the surface of the nutrient medium in the manner of liquid crystals, filling it with a dense layer, shimmering with all the colors of the rainbow.
A few days later, this layer thickened, and its central parts faded and filled with rod-shaped cells. When water was added, the rods quickly climbed out, ready to give rise to new bacterial colonies.
Unlike the “multicellular” structures that some other bacteria form, HS-3 doesn’t just contain different types of cells.
These cells differ in shape, appear at different stages of the life of the colony, and react differently to changes in the environment (appearance of water).
Obviously, this is due to the unusual living conditions of HS-3. They live on the walls of caves, above water streams, and when moisture reaches the colonies, they immediately throw out stick cells that spread with the flow.
Note that these bacteria cannot be called truly multicellular. Unlike human cells, many other animals and plants, HS-3 are able to survive and multiply and singly, independently of each other.
Nevertheless, such microbes, located on the primitive steps of multicellularity, allow us to better understand how it appeared and developed in the distant past.
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