"Synthetic biology has already delivered engineered organisms that can churn out a malaria drug, cook up an ideal biofuel or act as biosensors, but questions remain about how such organisms can be eliminated from the environment after they have performed their task. A team of US biotechnologists now thinks it has the answer: gene networks that can count. Endowing cells with this ability could lead to strains with a programmable shelf life, they say. For around a decade, synthetic biologists have been programming cells to detect and respond to external signals, or to hold a memory of past experiences. James Collins's team at Boston University, working with colleagues at the Harvard-MIT Division of Health Sciences and Technology, has designed synthetic gene networks that do both at the same time to build the first synthetic biological systems that can count." - Steven Perez from Bookmarklet