How engineered microbes could help feed the world’s crops

Engineered microbes that can colonize root zones and then switch on nitrogen-fixing genes are being tested to reduce reliance on synthetic fertilizer, which accounts for about 2% of global greenhouse-gas emissions. Switch Bioworks’ approach uses a genetic switch that triggers ammonia production when soil nitrogen drops, and early corn trials in six U.S. states have shown visibly healthier plants, though commercial rollout is still two to three years away.