Microbiology

Scientists Create First Semi-Synthetic Organism

The scientist at Scripps Research Institute has been designing bacteria having unnatural bases i.e. other than common bases of DNA G, C, A & T. These new unnatural bases are named as X and Y.

The beginning of life on earth is started by just letters in its genetic code (just four letters). On this earth, every organism’s proteins are spelled by the genetic code instruction (as we know all proteins are encoded by genes. These scientists have a belief that someday these unnatural bases will help in producing new molecules for medical therapies. According to a new study published in nature, a semi-synthetic strain of E. coli has been made which has X and y bases in its DNA and these bases guide cell to synthesize a new protein.

Fluorescent cells express a protein encoded by artificial DNA bases (Credit: Bill Kiosses, The Scripps Research Institute)

It is the first time that proteins are made by translating bases other than natural one. By including these two new bases X and Y, 152 new amino acids could be coded by an organism. As we know only 20 amino acids can be encoded by four bases. Researchers are hoping that new medicines can be made by using these new amino acids as building blocks.

“I would not call this a new lifeform—but it’s the closest thing anyone has ever made,” said TSRI Professor Floyd Romesberg, Ph.D., who led the study. “This is the first time ever a cell has translated a protein using something other than G, C, A or T.”

In 2014, Rosenberg and team announced the creation of semi-synthetic strain containing a copy of X and Y in its DNA. During their study, researchers also found that bacteria can easily pass on these unnatural bases to their daughter cells and can stably store it. But the main aim of this research is not only to store these bases but to transcribe it into RNA or to translate into protein so that it can be of therapeutic use.

For this Rosenberg and his colleagues embedded the unnatural bases in genes that contained A, C, G, T and transcribed those genes of semi-synthetic organism into RNA molecules. They also found that the cell could easily integrate these unnatural amino acids into their proteins. The protein which was produced into the process was found to be a GFP variant (GFP is the glowing marker often used in a genetic expression).

During this research, researchers also found that hydrogen bond is not as important for the stableness of DNA structure as many as scientists thought. In fact, they also found a force that can effectively contribute to every step of information storage and recovery of DNA. The scientist made the part of X and Y hydrophobic so that they won’t form the pair with other normal bases. So during this research, scientist studied that lack of complementary cell does not bother cell and X and Y were transcribe and translated successfully. He also said that hydrophobic bonds are actively participating.

According to researchers, this is just a small successful step. It will take time for unnatural bases to be replicate independently i.e. without being sandwiched between natural bases.The scientists added that without right chemicals it is impossible for the semisynthetic bacteria to survive so they can only stay alive in the laboratory in an artificial environment.

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