"The host is prompted to commit suicide by the bacterium, and this really nullifies the capacity of this cell to signal the other cells that there's a danger," says Falkow. "They taken out our first line of defense, the cells that are always on guard to tell the members of the more formalized immune system that they're in trouble.

"It's a battleground at a microscopic level between invaders and the defender. Like guerrilla warfare artists, these bacteria cut the lines of communication, and they do it by stealth."

All the while, the bacteria are preparing for their escape and for the obstacles they'll encounter after they break out of the cell. "They're not only fresh from replication, they also seem to be even more aggressive than before, as if they've adapted to intracellular life inside the host."

Cell Death

Once they invade a human cell, Salmonella establish themselves and eventually kill their host. Video provided by Stanley Falkow. 1.7 Megabyte QuickTime Movie with no audio. Click on the image to view.

Stanley Falkow answers the Question, "Are Bacteria Evil?"
Falkow is openly admiring as he describes the adaptability of pathogenic bacteria and the changes they undergo during the infection process. "When a bacterium first comes into the host, it's coming from contaminated food and water, which from a bacterial standpoint is a cold, cruel world. Once inside the stomach and intestinal tracts, it's bathed in nutrients and bile before it reaches its target in the small bowel and penetrates into the cell. It undergoes an awful lot of different obstacles and different chemical environments and in each case the organism is sensing where it is and what it's supposed to do. It's almost a choreography that the organism undergoes.

Microbe Spy


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