New 'Semi-Synthetic' Organism Formed Under Unique 6-Letter Genetic Code

Scientists may have heralded the rise of a totally new life form. A team of scientists has engineered the first ever "semi-synthetic" organism, courtesy of breeding E. coli bacteria with an expanded six-letter genetic code.

Every living thing on Earth is formed according to a DNA code using four bases, as in G, T, C, and A codes. However, the modified E. coli carry new types of DNA, additionally two new bases namely X and Y.

The team is led by Floyd Romesberg from the Scripps Research Institute in California. Their team created synthetic nucleotides or molecules that serve as the building blocks of DNA and RNA to create an additional base pair and have inserted this into the genetic code of the E. coli.

Now the world has seen its first semi-synthetic organism, with a genetic code of two natural base pairs and an additional "alien pair."

The researchers reported that these new organisms now provide a suitable platform to create living things with wholly unnatural attributes that cannot be found in nature.

According to Nature, the team actually announced that they have successfully engineered a synthetic DNA base pair made from the X and Y molecules back in 2014. Since then, they have been working on getting their modified E. coli to not only take the synthetic base pair into their DNA but to hold onto it for their lifespan.

The engineered bacteria were initially weak and sickly and soon died. Over the years, they devised three methods to engineer the new version of E. coli that could hold onto these new pairs indefinitely.

The first was to build a better version of a nucleotide transporter, which transports pieces of the synthetic base pair into the DNA.

The next is to change the molecule they used to make the Y base and found it could be easily recognized by enzymes in the bacteria that synthesize DNA molecules via replication.

In a report from Science Alert, the last method is to use CRISPR-Cas 9, a revolutionary gene-editing tool, to engineer E. coli that do not register the two new base pair as foreign invaders.