Great turning point: People have 'programmed' bacteria

Scientists have succeeded in producing E. coli with artificial original DNA, not from nature.

Researchers at Cambridge University say they have rewritten the DNA of Escherichia coli, creating a four-fold synthetic genome and much more complex than any previous attempt.

The bacteria have lived well. Despite their relatively irregular and reproductive shapes, their cells work in a purely biological set of rules, creating a familiar protein.

This achievement could one day create a creature that produces new drugs or other valuable compounds. These synthetic bacteria may also provide clues about how DNA codes were born in the early stages of life on our planet.

Big milestone of biotechnology industry

That is the affirmation of Tom Ellis, director of the Center for Synthetic Biology at the Royal University of London."No one has ever done this before , " he said.

Each gene in the genome of life is encoded only by four basic molecules, adenine, thymine, guanine and cytosine (often described by the first letters: A, T, G, C). A gene can be made up of thousands of such molecules.

Color scan of E. coli bacteria.Scientists at the University of Cambridge have created bacteria with re-encoded DNA.(Photo: Carl Zimmer).

Gene is a 'guide' to cells that produce different proteins for organisms. Protein performs most of the work in the body, from transporting oxygen in the blood to generating force in human muscles.

Nine years ago, researchers built a genome that synthesizes a million pairs of molecular pairs. The new set of E. coli genes consists of four million pairs of molecules, built using completely new methods.

The study was led by Jason Chin, a molecular biologist at Cambridge University, England. The production of each amino acid in the cell is driven by three molecules of molecules arranged in the DNA sequence. Each of these trio is called a codon. For example, the TCT codon ensures that an amino acid called serine is attached to the end of each new protein.

Because there are only 20 amino acids, scientists think the genome only needs 20 codons to create them. But our genetic code is abundant, for reasons no one understands.

In fact, amino acids are encoded by 61 codons and not 20. For example, the production of serine is regulated by six different codons. (Three of those codons are called stop codons, letting DNA know where to stop the sequence of one amino acid).

Like many scientists, Dr. Chin is intrigued by the excess of the genome. Are all these DNA fragments necessary for life?

'Because of the common life forms that use 64 codons, we really don't have the answers to the rest of the genome' , Dr. Chin said. Therefore, he tried to create a living creature to find the answer.

A color scan of the electron microscope of Mycoplasma mycoides, showing the image of a bacterium containing a genome containing one million base pairs.Now scientists have created an E.coli genome four times larger.(Photo: Thomas Deerinck).

After some preliminary experiments, he and his colleagues designed a modified version of the E. coli genome on a computer, requiring only 61 codons to produce all of the organism's amino acids.

Instead of requiring six codons to create serine, the genome uses only four. It has two stop codons instead of three. In fact, the researchers treated E. coli DNA as if it were a giant text file, performing search and replacement functions at more than 18,000 points.

Now researchers have a detailed design for the new genome of four million pairs of molecules. They can synthesize DNA in the laboratory, but putting these DNA into bacteria is a difficult challenge. This is like replacing natural DNA with artificial DNA.

The set of genes is too long and extremely complex to put into a cell. The researchers built small segments and swapped each piece in the genome of E. coli. Finally, E. Coli's entire gene was replaced by 100% artificial genes.

Fortunately, artificial E. coli did not die. These artificial bacteria grow more slowly than regular E. coli. They develop longer rod cells.

Dr. Chin hopes to build on this experiment by removing many codons, while compressing more genetic code.

Still very expensive

The Cambridge team is just one of many research groups to build a synthetic genome. The applications of this technology are numerous, but most significantly, the antiviral capabilities of artificial genes .

Many companies today use genetically modified bacteria to create drugs such as insulin or useful chemicals such as cleansing enzymes. If a viral outbreak attacks fermentation tanks, it will be disastrous. However, bacteria with synthetic DNA will be immune to such attacks.

The technology for making bacteria is still very expensive.(Photo: Rankred).

Scientists can also program cells so that their genomes do not work in other species, a type of 'biological firewall'.

In addition to the 20 amino acids used by all living organisms, there are hundreds of other types. A compressed genetic code will release the codons used by the genome to produce many other proteins. However, this technology is still very expensive.

E. coli has clearly demonstrated that its genome can be synthesized. So it won't be far away when we start 'programming' other species. ' In theory, you can program any living thing,' said a biologist.