Novel Insecticidal Toxins From Bacteria, UK

A light-emitting strain of bacteria and a nematode worm, which work together to prey
on soil-dwelling insects, use insecticidal toxins to kill their insect hosts. Scientists
speaking today Wednesday 5 September 2007 at the Society for General
Microbiology's 161st Meeting are now investigating the potential role of these toxins
in bacteria pathogenic to humans. The meeting is at the University of Edinburgh,
UK, and runs from 3-6 September 2007.



Speaker Michelle Hares, of the University of Exeter, studies insect-killing nematode
worms which have symbiotic bacteria living in their guts. When the worm encounters
insect prey, it burrows into the insect's body and regurgitates the bacteria. These
bacteria, called Photorhabdus luminescens, then release toxins directly into the
insect's bloodstream, rapidly killing it. The insect's flesh then provides food for the
bacteria and in turn the bacteria are food for the nematode.



"Once inside an insect, caterpillar or larva, the bacteria release a mixture of toxins
which kill the victim", says Michelle Hares of the University of Exeter's Cornwall
Campus. "The toxins we identified are made up of three different proteins, and all
three are needed to kill the insect". The Cornwall based scientists also discovered
that the same genes needed to make these protein toxins are found in the Yersinia
pestis bacteria which caused the bubonic plague, and in Yersinia
pseudotuberculosis which causes thousands of cases of gastroenteritis today.



When the toxic proteins from both these human pathogenic bacteria were fed to
tobacco hornworm caterpillars they had no effect, but when the same proteins were
put on living cells from humans both Yersinia bacteria strains killed the cells.



"Our initial interest in this group of toxins, was centered around the hunt for novel
insecticides, but our work now suggests they may also play an important role in the
evolution of human and mammalian disease", says Michelle Hares. "Our findings
suggest that insecticidal toxin complexes have been adapted by the Yersinia family
of bacteria to attack mammalian cells. We are therefore currently investigating
exactly how the toxin complexes elicit their response and how they are involved in
the evolution of pathogenic disease in Yersinia".




Mrs Hares is presenting the poster 'Insecticidal Toxins of Photorhabdus luminescens and
Yersinia' at 1400 on Wednesday 05 September 2007 in the Cells & Cell Surfaces Group
session of the 161st Meeting of the Society for General Microbiology at the University of
Edinburgh, 03 - 06 September 2007.




Full programme details of this meeting can be found on the Society's website here. Hard copies are available
on request from the SGM.




The Society for General Microbiology is the largest microbiology society in Europe, and
has over 5,500 members worldwide. The Society provides a common meeting ground for
scientists working in research and in fields with applications in microbiology including
medicine, veterinary medicine, pharmaceuticals, industry, agriculture, food, the
environment and education.



The SGM represents the science and profession of microbiology to government, the media
and the general public; supporting microbiology education at all levels; and encouraging
careers in microbiology.

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