September 15, 2006

Popeye's Greens

I've had something of a problem with the hyperventilated warnings issued by the FDA about bagged spinach "infected" with E. Coli. As anyone who's taken a course in microbiology knows, E. Coli is rather ubiquitous in the human gut, so it didn't strike me as a murderous microbe on par with Bubonic Plague. Mainstream news hasn't really clarified the situation much, either... falling into a familiar alarmist rut without actually understanding or communicating the nature of the problem. It turns out that the danger is real, and created by a very specific strain of E. Coli called O157:H7. According to blogger and science writer Carl Zimmer it has some fairly unfriendly properties:

Once it gets in our bodies, E. col O157:H7 starts causing serious trouble. It builds a needle that it can jab into the cells of our guts. Through it they inject a cocktail of molecules. One of the first of these molecules is a receptor, which inserts itself into the wall of the intestinal cell. In other words, Escherichia coli makes our cells part human, part microbe. The receptor can take in more of the molecules Escherichia coli O157:H7 produces, which alter how the cell reads its genes. Over 2000 genes in the cell change their patterns of expression. Some genes make more proteins and others shut down.

As its genes are manipulated, the cell begins to behave oddly. The skeleton-like fibers that support the cell begin sliding over one another to create a new shape. A pedestal-shaped cup rises from the top of the cell, offering Escherichia coli O157:H7 a place to rest. The cell also begins to leak fluids, which rush past the microbes. Safely cradled on their pedestals, the microbes can absorb nutrients in the flow. They also release toxins that dislodge hemoglobin, the oxygen-ferrying molecule, from blood cells. O157:H7 needs iron to grow, and hemoglobin is an iron-rich molecule. As the host bleeds, the microbe pulls fragments of hemoglobin into its interior and prizes the iron atoms free.

These changes cause blood diarrhea, but they are not the worst of Escherichia coli O157:H7's symptoms. Sometimes a few of the bacteria swell with toxins and burst.Their toxins enter our own cells, where they jam up the cellular factories that build proteins. Unable to make new proteins, the cells die and burst open. These toxins can slip into the blood vessels lining the intestines and soon spread to other organs. The kidneys are especially vulnerable to their attacks.

So this isn't the E. Coli we know. I'm not sure why MSM doesn't bother to tell us this stuff, but the performance seems on par with their war coverage.

Posted by Demosophist at 03:29 PM | Comments (0)