Reconstitution of Spiroplasma swimming by expressing two bacterial actins in synthetic minimal bacterium

Motility is one of the most important features of life, but its evolutionary origin is still unknown. Here, we focus on Spiroplasma , commensal or parasitic bacteria. They swim by the helicity switching of a ribbon-like cytoskeleton composed of six proteins each evolved from a nucleosidase and a bacterial actin called MreB. We expressed these proteins in a synthetic minimal bacterium, JCVI-syn3B whose genome was computer-designed and chemically synthesized. The synthetic bacterium showed swimming motility with the features common with Spiroplasma swimming. Moreover, some combinations of two proteins showed helical cell shape and swimming, suggesting that the swimming was originated from differentiation and coupling of the bacterial actin. One-Sentence Summary Expression of two bacterial actins gave cell helicity and swimming to a synthetic minimal cell. ### Competing Interest Statement The authors have declared no competing interest.