200709 spider prev

Doing spiders out of a job

Spider silk has a lot going for it. It’s strong, very light, biodegradable and biocompatible, and has the potential to be used in everything from tear-resistant clothing to aerospace components.

The Golden Silk Spider (Nephila clavipes). Credit: RIKEN

The one downside is that it tends to be in short supply because only spiders produce it, and they’re slow. But that might be about to change.

Japanese researchers say they have succeeded in producing the thin threads, or draglines, by using photosynthetic bacteria.

Writing in the journal Communications Biology, a team led by Keiji Numata at the RIKEN Centre for Sustainable Resource Science says the photosynthetic bacterium Rhodovulum sulfidophilum is ideal for establishing a sustainable bio-factory because it grows in seawater, requiring only carbon dioxide, nitrogen and solar energy.

They genetically engineered it to produce MaSp1 protein, the main component of the Nephila spider dragline which is thought to play an important role in the strength of the spider silk.

By optimising the gene sequence that they inserted into the bacterium’s genome, they were able, they say, to maximise the amount of silk that could be produced.

They also found that a simple mixture of artificial seawater, bicarbonate salt, nitrogen gas, yeast extract and irradiation with near-infrared light allowed R. sulfidophilum to grow well and produce the silk protein efficiently.

Further observations confirmed that the surface and internal structures of the fibres produced in the bacteria were very similar to those produced naturally by spiders.

“Our current study shows the initial proof of concept for producing spider silk in photosynthetic bacteria,” Numata says. “We are now working to mass produce spider-silk dragline proteins at higher molecular weights in our photosynthetic system.”

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