Silicon is the second most common element in the Earth’s crust, after oxygen. However, aside from its non-organic use by certain sea sponges and microorganisms, very little silicon is used by Earth’s biology, despite making heavy use of other common elements, such as carbon, hydrogen, iron, magnesium and oxygen. This has presented a long-standing puzzle for scientists: why would nature ignore such an otherwise useful substance?
While artificial methods of binding carbon and silicon have been available for some time, researchers with the California Institute of Technology were curious to see if they could get an organism to produce the same result, as a product of its metabolism. They selected the gene for producing an enzyme that could accomplish this from a bacterium, Rhodothermus marinus, that lives in Iceland’s hot springs, and introduced the involved DNA into a strain of ordinary E. coli bacteria.
When fed a particular type of silicon-containing precursors, the enzyme produced by the modified bacteria began catalyzing the silicon-carbon bonding process. After tweaking the bacteria with specialized mutations, the team was able to produce microbes that showed an increased efficiency in producing the silicon-organic compounds, to the point where they could out-produce artificial production methods.
“It’s remarkable that nature is poised to do all sorts of wild things in the presence of this new manmade food,” exclaims study lead and CalTech chemical engineer Frances Arnold. Arnold hopes that this development will help researchers understand if there was a reason as to why Earth biology evolved to exclude silicon, or if it was just a matter of luck. “We can start to explore what are the costs and benefits of incorporating silicon into life.”
While nature mightn’t have had as much of a use for it, humans have incorporated silicon into modern technology, capitalizing on the element’s properties, from the piezoelectric properties exhibited by quartz crystals, to the growth of silica wafers for microchips. And this is where the divide between man and machine could possibly be bridged: this new biological Si-O bonding process could one day lead to the melding of silicon electronics to carbon-based human tissue. This could potentially allow us to directly benefit from advantages that are currently only found in machines: the instant download of knowledge directly into our brains, medical diagnostic nanomachines — a new world of possibilities.
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