Researchers from the Osaka City University, the Osaka Metropolitan University and the Bioproduction Research Institute have created a swimming synthetic bacterium from the actively swimming crustacean pathogen Spiroplasma eriocheiris and a non-motile synthetic bacterium.
Reconstitution of Spiroplasma swimming in JCVI-syn3B by expressing seven genes. Image credit: Kiyama et al., doi: 10.1126/sciadv.abo7490.
“Studying the world’s smallest bacterium with the smallest functional motor apparatus could be used to develop movement for cell-mimicking microrobots or protein-based motors,” said lead author Professor Makoto Miyata, a researcher at the Osaka Metropolitan University.
Using genetic engineering, Professor Miyata and colleagues introduced seven proteins — believed to be directly involved in allowing Spiroplasma eriocheiris to swim — into a synthetic bacterium named JCVI-syn3B.
JCVI-syn3B was designed and chemically synthesized to have the smallest genomic DNA possible including the minimum essential genetic information required for growth from the smallest genomes of naturally occurring Mycoplasma bacteria.
“In 2016, scientists with the J. Craig Venter Institute (JCVI) created a synthetic bacterium called JCVI-syn3.0 as a combination of a cell of Mycoplasma capricolum and a genome designed on the basis of Mycoplasma mycoides,” the researchers explained.
“Both Mycoplasma species belong to the Spiroplasma clade, one of four Mollicutes clades.”
“JCVI-syn3.0 has the genome of minimal gene set and a fast growth rate, which is beneficial for genome manipulation, roughly spherical morphology, and no motility.”
“The next version of JCVI-syn3.0, JCVI-syn3B, has 19 genes returned from Mycoplasma mycoides for better growth,” they added.
“In our study, we reconstituted Spiroplasma swimming in JCVI-syn3B by adding seven genes and identified the minimal gene set for Spiroplasma cell helicity and swimming.”
The genetically re-engineered JCVI-syn3B changed from its normal spherical shape into a spiraling helix, which was able to swim by reversing the helix’s direction just like Spiroplasma.
The further experiments revealed that only two of these newly added proteins were required to make JCVI-syn3B capable of minimal swimming.
“Our swimming JCVI-syn3B can be said to be the ‘smallest mobile lifeform’ with the ability to move on its own,” Professor Miyata said.
“The results are expected to advance how we understand the evolution and origins of cell motility.”
The findings appear in the journal Science Advances.
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Hana Kiyama et al. 2022. Reconstitution of a minimal motility system based on Spiroplasma swimming by two bacterial actins in a synthetic minimal bacterium. Science Advances 8 (48); doi: 10.1126/sciadv.abo7490
