Rapid Virulence Annotation (RVA) is the new method that scientists at Universities of Bath and Exeter have devised for screening toxic genes in disease-causing bacteria which infect insects and humans. This novel approach, the results of which could lead to new vaccines and anti-bacterial drugs, was developed after studying a bacterium called Photorhabdus asymbiotica (which generally infects and kills insects and sometimes causes an unpleasant infection in humans). The researchers tested groups of genes from the bacteria against three types of invertebrates (insects, worms and amoebae) and mammalian cells.
They then identified toxins and other molecules, called virulence factors, made by the bacteria that allow it to infect each type of organism.
After pointing out the genes responsible for each of these possible virulence factors and comparing them with the genes of well known bacteria, the scientists have been able to map out which regions of the bacteria’s DNA control its ability to infect and damage invertebrates, and also potentially humans.
“Many bacteria have evolved to infect one particular type of plant or animal and most of the toxins they use to do this also have an effect in other hosts,” said Dr Nick Waterfield from the University of Bath’s Department of Biology & Biochemistry.
He added: “Some of the toxins they use for infecting can also allow the bacteria to jump across into another species like humans, perhaps with fatal consequences.”
Dr Maria Sanchez-Contreras, who works with Dr Waterfield at the University of Bath said: “We have developed a new way of discovering a greater number of previously unknown toxins and measuring how dangerous or virulent these bacteria are. Identifying the genes responsible for the production and secretion of these bacterial toxins will allow us find ways to prevent disease.
Richard ffrench-Constant, Professor of insect microbiology from the University of Exeter’s Cornwall Campus added: “RVA allows us to look for virulence factors that are totally novel and does not rely upon traditional searches based on factors already known from other bacteria. We have already discovered that some totally unexpected genes are indeed involved in bacterial virulence. This technique should prove to be a gold mine for potential vaccine candidates.”
The findings of the study have been published in the prestigious journal Proceedings of the National Academy of Sciences of the United States of America.