Genome sequence of the world's most lethal toxin

Botulism toxin is the deadliest poison on the planet. 2kg of it is enough to kill every person on the planet - although this doesn't stop the rich and tasteless from injecting it into their faces as Botox, where it stops nerves from working and has a slight smoothing effect on wrinkles. The toxin is produced by the Clostridium Botulinum bacteria - and scientists at the UK's Wellcome Trust Sanger Institute have just completed some fascinating genome research on the development of this incredibly effective killer and its survival mechanisms. Where some bacteria use complex and even elegant methods to dance around our immune systems, C. Botulinum goes for the direct hit with a "microbial sledgehammer." More please, just around the jawline.

The genome of the organism that produces the world's most lethal toxin is revealed today. This toxin is the one real weapon in the genome of Clostridium botulinum and less than 2 kg - the weight of two bags of sugar - is enough to kill every person on the planet. Very small amounts of the same toxin are used in medical treatments, one of which is known as Botox®.

The genome sequence shows that C. botulinum doesn't have subtle tools to evade our human defences or tricky methods of acquiring resistance to antibiotics. It lives either as a dormant spore or as a scavenger of decaying animal materials in the soil, and doesn't interact with human or other large animal hosts for prolonged periods of time.

Occasionally it gets into a living animal, via contaminated food or open wounds, leading to infant botulism or wound botulism, both of which are serious human infections. The host can be quickly overpowered and, in some cases, killed by the toxin, and C. botulinum has a new food source.

"Although in the same group as Clostridium difficile - the Cdiff superbug - C. botulinum has a genome that is remarkable because it is so stable," commented Dr Mohammed Sebaihia, lead author on the paper from the Wellcome Trust Sanger Institute. "Unlike Cdiff, in which more than 10% of genes have been acquired from other bacteria, there is almost no footprint of these in C. botulinum."

There are several types of C. botulinum: although described as variants of a single species, they are really very different organisms linked simply because they have the deadly toxin. For each type, there is also a near-identical but harmless relative that lacks the toxin. C. sporogenes is the non-malignant, near twin of the organism sequenced.

Professor Mike Peck, from the Institute of Food Research, commented that "It is astonishing that 43% of the predicted genes in the C. botulinum genome are absent from the other five sequenced clostridia, and only 16% of the C. botulinum genes are common to all five. Our findings emphasise just how different clostridia are from each other."

C. botulinum toxin stops nerves from working - the basis of its use in medicine to control tremors and in cosmetic treatments. For the prey of its opportunistic attacks, death is swift. Perhaps the most important tool it has to act out its stealth attacks is its ability to hibernate when times are hard by forming dormant spores.

...continued