Here\u2019s what you\u2019ll learn when you read this story:<\/p>\n
Most organisms on Earth have the same basic genetic code, but it comes with some flaws.<\/p>\n<\/li>\n
Scientists sought to work out those errors by creating their own artificial genome, which replaced E. coli\u2019s original genome and used less genetic material.<\/p>\n<\/li>\n
Future applications of this could create enhanced organisms that are, among other things, virus-resistant.<\/p>\n<\/li>\n<\/ul>\n
The genetic code for just about all forms of life on Earth is fairly universal<\/a>. It has the same 64 codons (sequences of nucleotides<\/a>), molecules that both encode the amino acids (which encode the formation of proteins) and create the bases of nucleic acids such as DNA and RNA. Why mess with something that hasn\u2019t changed in billions of years?<\/p>\n Despite nature having its reasons for leaving some things unchanged, biologist Jason Chin from Oxford University, still decided to change things up. It turns out some codons have extra copies of directions for encoding amino acids and signals for switching the formation of proteins on and off. Chin wanted to see if life could still function with less. He already managed to prove that when he synthesized Syn61<\/a>\u2014E. coli bacteria with three fewer codons than before. But now, he has gone even further with the synthetic organism Syn57\u2014E. coli with a 57-codon genome.<\/p>\n Narrowing down the codons that encode protein synthesis can make some organisms resistant to viruses\u2014synthetic genetic codes<\/a> transferred to organisms can actually block viruses, which genetically alter an organism by injecting cells with RNA that carries codes for producing viral proteins<\/a>. It can also enable more efficient protein synthesis and help build protein polymers (chains of at least 500 amino acids). Protein polymers<\/a> can behave like natural proteins, but they can also be designed to solve problems on a molecular level.<\/p>\n \u201cEmerging methods for the total synthesis of genomes provide opportunities to explore genome sequences that cannot be accessed by editing,\u201d Chin and his research team said in a study recently published in Science<\/a>. \u201cSynthetic genomes may be radically different from those accessed by natural evolution, and genome synthesis provides a route to generating sequence and function that is [nonexistant] with respect to extant life.\u201d<\/p>\n Previously, other teams of researchers have removed stop codons<\/a>, which signal protein synthesis to end, from the E. coli genome. This was done through mutagenesis<\/a>, or creating gene mutations by tweaking DNA. However, mutagenesis has its downsides\u2014it often ends up with excess mutations, and can have difficulty adjusting the numbers of sense codons<\/a> (which encode amino acids) versus stop codons.<\/p>\n Syn61 already showed how organisms could survive with just 61 codons, but the question was whether or not that was the limit. In synthesizing the genetic code for Syn57, Chin swapped out repeating codons and made over a hundred thousand codon changes to the original. Some re-coded groups of codons needed to be tolerated over an entire region of the genome, while in other cases, a codon only needed to be replaced with a viable substitute. He then assembled the DNA into an artificial chromosome<\/a>, introduced it into the E. coli genome (this was done for each group of codons), and sequenced the clones to see how successful they were.<\/p>\n Several strains of E. coli were cultured before the final version emerged. As bacterial strains within the lab-created genome cloned themselves, they were analyzed for growth. Taking a closer look at two strains revealed that recoded regions of the genome actually limited growth. When more alterations were made to these sections of the genome, however, growth improved in these strains. It was the final synthetic strain that Chin named Syn57. In upcoming research, he plans to continue testing the limits of a genome.<\/p>\n