One step closer to artificial life

Researchers at J. Craig Venter Academy (JCVI), a nonprofit genetic research organization, have published results describing the method in which the entire genome of Mycoplasma mycoides is copied in a yeast cell by adding a yeast plasmid chain to the bacterial chromosome. The researchers transformed this chain in yeast cells using the yeast genetic system. The modified bacterial chromosome then continued to be isolated from the yeast and transplanted into a relative species of bacteria, Mycoplasma capricolum, to create a new form of M. mycoides cell.

This is the first time the genome has been transferred between different branches of life - from a prokaryote to eukaryote and back to the prokaryote. The study was published in the August 21 issue of Science.

Hamilton Smith, one of the leaders of the JCVI team, said: 'I believe this research has important implications for improving our knowledge of the fundamental basis of biology to advance to the final stage in making a synthetic genome. This may be one of the most important findings in the field of gene synthesis'.

This study is based on a previous breakthrough at JCVI. In 2007, the team published results from the transplantation of the M. mycoides genome into M. capricolum cells and led to the M. capricolum cell being transformed into M. mycoides. This study established the concept that DNA is the 'software' of life and it is DNA that determines the genotype.

In 2008 the team reported on the construction of the first synthetic bacterial genome by assembling DNA fragments formed from four chemicals of life - ACGT. The introduction of DNA fragments into the genome is done in yeast using the yeast genome system. However, when the team tried to transplant the synthetic bacterial genome into a bacterial cell, all experiments failed.

Previous researchers have confirmed that no proteins are needed during chromosome implantation, but they also show that DNA methylation (chemical alteration of DNA that bacterial cells use to protect Its genome from limited enzyme degradation, which is DNA-cutting proteins in specific locations, may be needed for this process. When the chromosome is isolated directly from the bacterial cell, it undergoes methylation and is therefore implantable because it is protected from limited enzymes.

Yeast. The entire genome of Mycoplasma mycoides is reproduced in a yeast cell by adding the yeast plasmid chain to the bacterial chromosome. The researchers transformed this chain in yeast cells using the yeast genetic system. The modified bacterial chromosome then continued to be isolated from the yeast and transplanted into a relative species of bacteria, Mycoplasma capricolum, to create a new form of M. mycoides cell. (Photo: Wikimedia Commons. Public Domain Image)

In this study, the team began copying the M. mycoides genome into yeast by adding a yeast medium to the bacterial genome. This is the first time that the bacterial genome has been successfully developed in yeast. The methylase enzymes are isolated from M. mycoides and used to methylate the M. mycoides genome isolated from yeast. When DNA is chromosome methylate can be successfully transplanted into a M. capricolum species. However, if the DNA is not methylate, the transplant experiments will not succeed. To prove that the restriction enzymes in M. capricolum cells were responsible for the destruction of the transplanted genome, the team removed the restriction enzyme genes from the M. capricolum genome. When the implantation of the genome was performed on limited enzyme-removed cells, all experiments succeeded regardless of whether DNA was methylate or not.

'The ability to transform the bacterial genome in yeast is an important step, expanding the genetic effect of yeast on bacteria. If this is extended to other bacteria, we believe that this method could be used in routine laboratory practices to transform organisms, ' said Dr. Sanjay Vashee, a researcher with JCVI is also the author of the article, said.

The team now has a complete cycle of genomic replication in yeast, transforming the bacterial genome as a yeast chromosome and transplanting the genome back to a bacterial cell to create a new strain of bacteria. These new methods will allow the team to achieve success in transplanting and activating synthetic bacterial systems. The study was published August 21 by JCVI researchers, and was funded by the Genomics Company, co-founded by Dr. Smith and Venter.

Refer:

1. Lartigue et al.Tạo Đường dẫn Băm nhỏ từ Genomes Có đã đã bị bỏ qua và Engineered in Yeast.Science, August 20, 2009;DOI: 10.1126 / science.1173759