ABSTRACT breaks down mind-blowing scientific research, future technologies, new discoveries and major breakthroughs.
Motility – the scientific term for the ability to move independently – is one of the most important characteristics for living organisms on Earth. But the origin of the cell’s ability to move remains a mystery to many scientists. However, new research in which scientists created the world’s smallest motile organism gives insight into how cell motility came about.
The study, which was published in Scientists progress Wednesday, is the result of a collaboration between graduate student Hana Kiyama, of Osaka City University’s Graduate School of Science, and Professor Makoto Miyatafrom the Graduate School of Science of Osaka Metropolitan University.
As the authors write in their paper, “Motility is observed in various phyla and arguably one of the major determinants of survival.” According to the article, cell motility is thought to arise from small movements of house proteins that are transmitted to a cell, but the proposed process has not been demonstrated experimentally. Their study is therefore a means of testing this theory.
In this experiment, the researchers genetically modified a synthetic bacterium named JCVI-syn-3b, or syn-3, which is nonmotile. To reconstruct syn-3, the group introduced seven genes that code for proteins likely involved in the swimming movement of spiroplasm bacteria. spiroplasm is a small bacterium known to “swim” by essentially changing its cytoskeleton. The introduced proteins evolved from the bacterial actin protein MreB. Actin is a multifunctional protein that is often responsible for cell motility. In an email to Motherboard, Miyata confirmed that prior to this experiment, no one had succeeded in making a minimally mobile synthetic bacterium.
“In a previous study, we suggested that cellular motilities evolved evolutionarily from housekeeping systems possessing movements,” Miyata told Motherboard in an email. “We intended to show evidence through experiments. We chose the spiroplasm system because we were also working on spiroplasm swimming.”
By introducing the proteins responsible for motility into spiroplasm in syn-3, the researchers succeeded in making the previously non-motile bacteria swim, as evidenced by a published video on the University’s YouTube account.
“We were surprised twice swimming by seven proteins and swimming by the proteins MreB4 and MreB5,” explained Miyata. “Hana Kiyama built these cells and observed the findings. She confirmed her observations and invited people in the same room to her microscope. We all understood immediately what happened, because we were waiting for his results with moderate stretches.
The researchers also wanted to see how the expression of different combinations of motility genes would affect bacteria genetically engineered to swim. In doing so, they found that expression of only two proteins was required to promote motility in syn-3, likely indicating that many proteins were redundant and demonstrating a minimal motility system.
“To the best of our knowledge, the motility system comprising only two proteins from the actin superfamily is the smallest system established to date,” the authors write. “Therefore, we can call it a ‘minimal mobile cell’.”
Although this study is primarily a proof of concept, it gives scientists a better understanding of how cell motility could have potentially originated and evolved.
In addition to the pure novelty of creating such a small swimmer, the new study sheds light on the origin of movement in the first mobile life forms to appear on Earth. For example, Miyata stated that the actin protein MreB is not involved in the motility of many other bacterial species, confirming that there are several different evolutionary pathways that have led to microbial movement.
“We are tracing the evolution from the ancestral MreB to the swimming MreB using the current system,” said Miyata, who added that the team was also testing other motility systems in their synthetic creature.
This also has implications for future creations. “The study of the world’s smallest bacterium with the smallest functional motor apparatus could be used to develop the movement of cell-mimicking microrobots or protein-based motors,” Professor Miyata said in a Press release.
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