Minimum mobile cell
Scientists have synthesized the smallest possible moving microorganism
Japanese scientists from Osaka University used a synthetic bacterium with the smallest possible genome to create the smallest creature capable of independent movement. The results of the study are published in the journal Science Advances (Kiyama et al., Reconstruction of a minimal motility system based on Spiroplasma swimming by two bacterial actins in a synthetic minimal bacterium).
During the experiment, experts used the DNA of spiroplasm — a small bacterium of the genus Mollicutes, leading a parasitic lifestyle, having a spiral shape and moving in an unusual way for such microorganisms. Instead of rotating like a propeller, the spiroplasmas change the structure of the cytoskeleton. This creates an "inflection" that moves along the body and switches the direction of the spiral, pushing the water. The cytoskeleton itself consists of six types of proteins, small displacements of which are enough to generate movement.
These genes were inserted into the genome of a synthetic JCVI-syn3.0 cell, first developed in 2016, and the genetically reconstructed syn3B changed its usual spherical shape to a spiral shape that could float using the same principle as the spiroplasm. Further investigation showed that combinations of two proteins — MreB4-MreB5 and MreB1-MreB5 — are enough for the cells to acquire a spiral shape and begin to swim.
According to the authors, the motility system, which includes only two actin proteins, is the smallest system that exists today, and can be called a "minimal motile cell".
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