Super-strength spider silk made by bacteria

If you’re scared of spiders but also need really strong silk, have no fear, because engineers at Washington University, US, have developed bacteria that can make super-strong spider-inspired fibres.

The bacteria were genetically engineered to artificially produce proteins very similar to spider silk, which has a lot of nanocrystals – the main source of strength in the silk.

“Spiders have figured out how to spin fibre with a desirable amount of nanocrystals,” says Fuzhong Zhang, who supervised the project. “But when humans use artificial spinning processes, the amount of nanocrystals in a synthetic silk fibre is often lower than its natural counterpart.”

The paper, published in ACS Nano, describes how the artificial silk – called polymeric amyloid fibre – is stronger than some spider silks because small changes to the protein code introduce more nanocrystals.

Read more: As tough as spider silk

The bacteria-produced proteins were amyloids – abnormal proteins – that consisted of 128 repeated amino acid sequences that maximised the number of nanocrystals but remained simple enough to be expressed by bacteria without difficulty.

A chart. The left axis says toughness. The botton axis says ultimate tensile strecgh. The red dot that shows the bacteria make sils is at the top right corner
This chart compares the toughness and strength of different natural and recombinant silk fibers. In red is the polymeric amyloid fiber developed in Fuzhong Zhang’s lab. Credit: Washington University in St. Louis/Jingyao Li

The fibres were stronger than common steel of the same diameter and required more energy to break than Kevlar – one of the materials used to build spacesuits.

“This demonstrates that we can engineer biology to produce materials that beat the best material in nature,” says Zhang.

The study explored just three of thousands of amyloid sequences, which means there may be a way to engineer the silk to be stronger than spiders’ natural silk, say the researchers.

“There seem to be unlimited possibilities in engineering high-performance materials using our platform,” says lead author Jingyao Li.

“It’s likely that you can use other sequences, put them into our design and also get a performance-enhanced fibre.”

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