Only 473 genes to bacteria are enough to stay alive and multiply every three hours as researchers have demonstrated J. Craig Venter Institute in La Jolla (California, USA) and the company Synthetic Genomics.
A third of these genes have no known function, which reveals that scientists still ignore fundamental aspects of how living things work
The bacteria, which is living with the world’s smallest genome being, not found in nature. It was created in the laboratory by typing its genetic sequence in computers, building your DNA as a layman with synthetic biology techniques and transplanted the genome of another bacterium that has been used as a surrogate mother Its creators named. JCVI-Syn3. 0.
The aim of the researchers, who presented the progress this week in the journal Science, is twofold. One is basic science: understanding what is necessary for life minimal genome and find out what the function of each of the genes essential for cell.
search ?? We started twenty years ago; we think that the only way to answer basic questions about life would get a minimal genome, and probably the only way to get it would be synthesizing ?? , said Craig Venter, who led the research.
The second objective is applied science: convert the minimum cell into a factory of organic products of commercial interest as drugs, food, tissues or biofuels. To do this, you should add some additional genes. ?? We think these cells have many advantages. For example, as each gene is essential, they have few mutations. They would be efficient in energy use. And, as are simple organisms, would be easy to design ?? , said Daniel Gibson, co-author.
Build the minimal genome cost Venter and his team more than five years in 2010 presented the first living being created by computer. On that occasion they showed they could design a genome from computer data and which, if introduced into a bacterium, the genome took control of the cell and began to self-replicate.
Using the same technique, they designed the minimal genome as they thought it should be. But every time I tried to give life to a cell from the DNA fragments had devised, the cell died. ?? The big news is that we fail ?? recognizes Venter quoted by Science. ?? Our current knowledge of biology is not enough to sit, to design and build a living organism ??.
instead of building the minimal genome from scratch, it would build by trial and error based on an existing bacteria.
They chose a bacterium of the species Mycoplasma mycoides, which causes respiratory infections in cattle, because it is the same one he had worked in 2010 and because it has a small genome with only 901 genes and one million base pairs ( or letters of the genome). By comparison, E. coli bacterium has more than 4,000 genes and the human species, more than 20,000.
With patience ant, researchers defused one by one the genes of M. mycoides to see which of them were vital. If bacteria were dying to be deprived of a gene, it was considered essential, so it should be of the minimal genome. If the bacteria survive, then the gene could be eliminated.
After completing the pruning process has been a genome half a million base pairs and 473 genes. The initial genome of M. mycoides, therefore, has halved. And the end result is 10% smaller than the smallest genome known to date, which belongs to the bacterium Mycoplasma genitalium and has 525 genes.
When the new genome was inserted into a bacterium, it has taken control of the cell and has begun to multiply. The new bacteria form colonies of spherical cells of various sizes and population doubles every 180 minutes, a relatively short period which is an advantage for future commercial applications.
Surprisingly, nearly a third of the essential genes (149 of 473) has no known function. ?? It is the most interesting result of research ??, highlights Luis Serrano, director of the Centre for Genomic Regulation (CRG) and specialist in synthetic biology whose work is cited in Science by Venter’s team.
Many of these genes are shared by multiple species, suggesting that handle very fundamental biological functions. ?? We know about two-thirds of the essential biology, ignore the other third; is an important lesson ??, Venter said in the press conference. ?? We are showing how complex life even in the simplest organisms ??.
According to Venter, this explains why all attempts to build the minimal genome from scratch fail. It was impossible to design a viable genome ignoring a third of its essential genes.
Another important result is that genes do not divide so sharp between essential and dispensable. Researchers have identified an intermediate category they call quasi-essential genes. Those ?? that are not absolutely critical to the viability but are needed for robust growth ?? , according to the definition proposed in Science.
Therefore, it recognizes Venter, the genome JCVI-syn3.0 is not the smallest possible. If it is accepted compromise growth, you could get an even smaller genome to continue to be viable. Or if, instead of working with bacteria of the genus Mycoplasma, had worked with other microorganisms, they might have managed to reduce more the genome.
In addition, Venter said, ?? each genome depends on the context ?? in which an organism lives. ?? It makes no sense to speak of a minimal genome if we do not define both the context and the phenotype ?? . According to him, the new bacterium is present inScience work ?? an approximation to a minimal cell ??
. Source: La Vanguardia
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