New technique for assessing essential genes in bacteria in one experiment

Research lead

Researchers at the Sanger Centre in Cambridge, UK, have developed a new technique that makes it possible to assess every gene in a bacterial cell in a single experiment, an advance that will transform the search for essential genes as targets in the development of antibiotics.

Using the new sequencing method, Transposon Directed Insertion Site Sequencing, the researchers have singled out the essential genes in Salmonella Typhi, showing that only 356 of 4,162 genes are essential for survival.

The method is ten times more powerful than existing methods according to one of the researchers, Gemma Langridge. “By combining transposon-induced mutagenesis, a method for disabling individual genes, and high-throughput sequencing, we have been able to determine which genes are essential for the survival of S. Typhi and which are non-essential. Crucially this can be done in a single experiment.”

The researchers have also applied the method to look at how S. Typhi survives in humans. Typhoid can be spread by carriers who, without showing symptoms, act as reservoirs, storing the bacterium in the gallbladder and passing it to others. Bacteria cannot survive in the fairly hostile environment of the gall bladder unless they are tolerant to bile, and thus looking at genes involved in bile resistance, makes it possible to single out the genes that are essential for allowing S. Typhi to persist in a carrier.