Bacteria with an expanded genetic code were obtained
A group of scientists from The Scripps Research Institute (TSRI), led by Professor Floyd E. Romesberg, published in the journal Proceedings of the National Academy of Sciences an article about the bacteria they obtained with an artificially expanded genetic code (Zhang et al., A semisynthetic organization engineered for the stable expansion of the genetic alphabet).
The DNA of all organisms on Earth contains four nucleotides: adenine, thymine, guanine and cytosine, which combine with each other in pairs, and adenine always combines with thymine, and guanine with cytosine. The sequence of such pairs is our genome. Now scientists have modified the genome of the E.coli bacterium by introducing two additional nucleotides, which no natural organism has. These two additional "letters" of the genetic alphabet are designated by Romsberg and his colleagues as X and Y.
Romsberg first reported on such an experiment in the summer of 2014. But the viability of the resulting bacteria was low, and they soon died. Over the past two years, scientists have been able to make their bacteria much hardier, as well as ensure the transfer of nucleotides X and Y to descendants during bacterial division. In particular, they had to modify the analogue of the immune system existing in bacteria so that it destroys any DNA molecules that do not contain elements X and Y.
The researchers say the modified microorganisms will be the starting point for creating "organisms with completely unnatural qualities and traits not found elsewhere in nature." Bacteria represent "a stable form of semi-synthetic life" and "lay the foundation for achieving the central goal of synthetic biology: the creation of new forms of life."
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24.01.2017