Decloaking the germ

The bacterium Listeria infects humans through contaminated food. Once in the gut, this pathogen can be life-threatening if contracted during pregnancy or by newborns and those with weakened immune systems.

But for most people, an encounter with Listeria causes nothing more than vomiting and diarrhoea because our immune system recognises the
long, propeller-like projections on the bacterial surface – called flagella – and
mounts an assault on Listeria until it is wiped out. Listeria, however, has evolved a way to dodge this fate.

To anyone who has ever tried to cross enemy lines, this bacterium has an enviable ruse. After detecting the warmth of the human body, Listeria shuts down the production of flagella – the equivalent of enveloping itself in an invisible cloak. It does this by activating a protein called motility gene repressor, or MogR for short, which binds to DNA close to the flagella gene and suppresses it.

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