For the first time, researchers have looked at the need for every gene in a bacterial cell in just one experiment. They showed that Salmonella Typhi — which every year infects 22 million people and causes 220,000 deaths — needs only 356 genes for survival: 4162 genes are not essential. The method, which harnesses next-generation sequencing technologies, will aid the search for weaknesses in bacterial armories, allowing researchers to seek treatments to target those genes.