The genome of the organism that produces the worlds 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 doesnt 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 doesnt 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 per cent 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 per cent of the predicted genes in the C. botulinum genome are absent from the other five sequenced clostridia, an
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Contact: Don Powell
press.officer@sanger.ac.uk
University of Nottingham
25-May-2007