Bacterial web
Biologists got a web of bacteria
Sergey Vasiliev, Naked Science
Many proteins created by billions of years of evolution of living organisms, their properties and capabilities surpass the best artificial materials obtained by man. For example, a web consisting of fibroin protein is lighter and stronger than the most durable steel grades. Unfortunately, it is not possible to establish its mass production, despite decades of active searches.
This is partly due to difficulties in the correct folding, "packing" of long polymer strands after synthesis. Partly – with the peculiarities of the composition of the protein polymers themselves and the genes encoding them. They contain exceptionally long repetitive sequences that make these genes unstable when introduced into someone else's body, be it bacterial cells, yeast, or even a plant or mammal, which have also been considered as potential producers of artificial webs.
Fuzhong Zhang, a biologist from Washington University in St. Louis, spoke about a possible breakthrough in this direction. Speaking at the American Chemical Society (ACS) exhibition and conference in Orlando, he reported on the first success in creating GM bacteria to produce fibroin and other "difficult" to synthesize useful proteins. Scientists managed to break the original fibroin genes into two smaller fragments and introduce them into bacterial cells. Having received the finished parts of the future protein, they were joined together.
To do this, the inserted fragments of the gene were supplemented along the edges with inteins – special sites that are used in nature to "splice" peptide fragments into large functional proteins. By connecting the ends, the inteins cut themselves out of the finished amino acid sequence. This also happened in the laboratory: having isolated the protein parts of spider silk from bacterial biomass, the scientists mixed them and started the reaction of the compound to form a target protein suitable for the production of threads.
Threads of synthetic web. Pictures from the press release of ACS Bacterial factories could manufacture high-performance proteins for space missions – VM.
According to Zhang, already at this stage, the method allowed to obtain more cobwebs than previously tested variants – up to two grams per liter of bacterial culture. At the same time, its properties turned out to be no worse, and by some indicators even better than natural: the tensile strength exceeded 1000 MPa, and the impact strength was 114 MJ/m3. The authors believe that the bacterial system they created will allow synthesizing other natural proteins difficult to produce, characterized by the presence of long repeating sequences.
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