Clostridium botulinum is the bacterium that causes botulism (a form of food poisioning). The bacterium produces a potent toxin that causes muscle paralysis by reducing the release of the neurotransmitter acetylcholine from motor neurons.  For many other bacteria, the value (from the point of view of the microbe) is clear (for example, cholera is spread by contamination of food and water with feces from infected individuals; the cholera bacterium produces a toxin that leads to massive watery diarrhea which increases the likelihood of contamination), but I don't see how this toxin helps Clostridium.

A condition called ‘pine mouth’ is on the rise. It is characterized by an extremely bitter taste in the mouth after eating or drinking. The bitter taste occurs the day after eating pine nuts, and lasts for up to 10 days. It does not happen to all individuals who eat the nuts, and appears to only be from certain batches of pine nuts. It has been suggested that a toxin on the surface of some imported nuts may be responsible. Can anyone provide a plausible biological explanation for this.

Marian Brennan

Newcastle, Wicklow, Ireland

I once read that apple pips contain cyanide. Is this substantial enough to be harmful to humans who choose to eat all of the apple, including the core? If it's not a high content, then how many pips would you have to eat to feel the effects?

Similarly, do other fruits also contain harmful amounts? Stones from peaches and plums are much bigger than the pips in an apple...

My husband says not to fuss, but I never feel relaxed eating at a table under a poisonous tree. Who's right ?