Researchers led by Imperial College London's Martin Buck report in Nature Communications their construction of a novel modular and orthogonal AND gate in E. coli using a Pseudomonas syringae module. This, says Gunnar De Winter at the Curious Cub, is another step toward a biological computer. "In short, environmental signals can bind to promoters and result in the activation of two genes, hrpR and hrpS. When the products of both genes are present, they bind to the activator sequence of another gene. The result of this is that a closed transcription complex is remodeled into an open one, leading to the transcription of the third involved gene, which is a reporter gene (gfp) that enables the researchers to see that their inputs result in the desired output," De Winter says.