New approach to check toxic genes in disease-causing bacteria devised
Washington, Oct 10 : After studying a bacterium called Photorhabdus asymbiotica,
scientists at Universities of Bath and Exeter have developed a new method, called Rapid
Virulence Annotation (RVA), for checking toxic genes in disease-causing bacteria which
infect insects and humans.
The results of the study could in the future lead to new vaccines and anti-bacterial
drugs.
Photorhabdus asymbiotica, normally infects and kills insects, but can also cause 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.
"Our new technique, called Rapid Virulence Annotation (RVA), allows us to make faster
assessments of the disease-causing agents in multiple types of organism; it lets us
pinpoint sequences of genes which may pose a risk to humans; and it gives us a powerful
tool to identify virulence genes in other known bacteria. Finally, it helps us identify
new targets for drugs to fight these diseases and control pests, and for developing
preventive vaccines."
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."
Already, researchers are using this relatively cheap and highly accurate RVA technique
in other disease-causing bacteria to identify the genes, which allow some diseases to jump
the species barrier.
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.
--ANI
