Full PDF (not open access): http://www.nature.com/nature/journal/v518/n7537/pdf/nature14121.pdf http://www.nature.com/nature/journal/v518/n7537/pdf/nature14...

Full PDF (not open access): http://www.nature.com/nature/journal/v518/n7537/pdf/nature14121.pdf http://www.nature.com/nature/journal/v518/n7537/pdf/nature14... Auxotrophy[1] been exploited for years to select for engineered organisms. Reverse mutation to prototrophic strain is often an issue. This work by Mandell, et al., is novel because it relies on the organism being auxotrophic for a non-standard amino acid, L-4,49-biphenylalanine. It's cool the system is stable. 1. https://en.wikipedia.org/wiki/Auxotrophy https://en.wikipedia.org/wiki/Auxotrophy