The bowels are a difficult place to live. It's damp and crowded and the landlord keeps trying to kick you out. Find out how salmonella uses the body's immune response to transform the inside of your body into someplace liveable.
The major problem with living in someone's intestinal tract is it's unlikely that you're next to the window. That means there's no way to get fresh air. In fact, there's no way to get air at all. Since respiration is a major way that living cells generate energy, the cells in the body fall back on fermentation. The products of fermentation are usually gases, which is why indigestion is so . . . fragrant.
Salmonella, though, isn't interested in brewing something. It wants to breathe, and it has figured out a way to do it. When cells that a body deems harmful show up, the body attacks them with oxygen radicals. An oxygen radical is a form of oxygen that needs another electron, and it's a hungry thing. It will grab one from anywhere. It rips into cells and damage DNA and RNA. Doesn't work that way with salmonella, though.
Although some Salmonella bacteria are killed by this response, many more benefit: the oxygen radicals create a sulfur compound called tetrathionate, which Salmonella are able to use instead of oxygen for respiration.
Interestingly, tetrathionate has been used since 1923 by microbiologists as a way to promote the growth of Salmonella in biological samples containing competing microbes. But because tetrathionate was not known to exist in living people, it was assumed prior to this study that this process had little relevance for food poisoning. Up until now, tetrathionate was believed to mainly exist naturally in decaying corpses or in thermal springs.
Salmonella literally takes a body's best shot at rubbing it out and uses the bullet to build its own atmosphere. First step, a salmonella atmosphere. Second, a salmonella planetary alliance. Third, a salmonella rebellion. Fourth, a tiny salmonella Captain Mal.