Given that botulism thrives in dented/damaged canned foods, why doesn’t it grow everywhere there is spoiled food on a surface for any extended period of weeks?
Or does it not like open air and light?
Clostridium botulinum forms inert spores in response to oxygen. In an oxygen depleted environment, like poorly sterilized canned food, the spores germinate to form the growing cells. These cells produce a pre-formed toxin that is harmful to us, even if the bacterial cells are later killed before consuming the food.
Just to clarify a little further…
It’s important to draw the distinction between the botulism spores, which are indeed everywhere, and the botulism toxin those spores produce in an anaerobic environment such as home canned food. The toxin is what poses the danger to us. Even that can be rendered harmless by boiling home canned food for 10 minutes. Of course, if you think the seal has been breached, throw it out. Boiling is done as a precaution.
OK, so food left at room temperature indefinitely, *exposed to oxygen, *will develop a variety of other nasty organisms, but not botulism spore growth?
Yes, the bacteria that cause botulism poisoning are anaerobic, meaning they won’t grow in the presence of oxygen.
BTW, botulism poisoning from canned foods may be caused not only by leaky containers, but by improper sterilization. The cans or jars must be heated and kept at a high enough temperature to kill any Clostridium botulinum spores. If this isn’t done right, unkilled spores can grow in the sealed can or jar and produce botulism toxin. These days this is more of a problem with home canning than with commercial products.
Botulism bacteria can also grow in aged sausage that is improperly cured. Nitrates and nitrates prevent the growth of the bacteria. Without these curing agents, botulism bacteria can grow in the interior of the sausage over time, producing toxin as they grow. The word “botulism” is derived from the Latin word for “sausage” (botulus). People got botulism from sausages long before canning was invented, so botulism was associated with sausages. Again, these days you’re more likely to get botulism from homemade sausage than from commercial sausage.