The Download: food from thin air, and finding new materials

A new crop of biotech startups, armed with carbon-guzzling bacteria and plenty of capital, are promising something that seems too good to be true. They say they can make food out of thin air. But that's exactly how certain soil-dwelling bacteria work. In nature, they survive on a meager diet of oxygen, nitrogen, carbon dioxide, and water vapor drawn directly from the atmosphere. In the lab, they do the same, eating up waste carbon and reproducing so enthusiastically that their populations swell to fill massive fermentation tanks.