by Janet A. Ginsburg

It’s official: Spinach has become a national obsession. And if real people weren’t suffering real ills, really dying, and finding themselves facing real bankruptcy, it would be kind of funny. Death by spinach? A good food turned bad? It’s so…Monty Python.

Or maybe it’s just business-as-usual biology running head-on into the speedy production schedules and broad distribution networks of 21st century agriculture.

Four years ago, a team of researchers in Karl Matthews’ lab at Rutgers University published

a study showing that the roots of lettuce plants were able to take up e.coli bacteria from soil treated with contaminated manure or contaminated water. Once safely inside, the bacteria

There is nothing particularly unusual about this. Soil is teaming with bacteria--and viruses--including harmless strains of e.coli. It makes sense that, just as plants absorb chemicals from the soil (an urban garden in Montreal recently had to toss their harvest when it tested off the charts for lead), they also take up microbes.

Most of the time, that’s not a problem. It may even be one

of the ways we acquire “good” bacteria. But O157:H7 is definitely a bug with fangs. By some estimates, an infection of as few as 10 cells is enough to send a person to the ER, doubled over and bloody. It is conceivable that only a leaf or two in a package of spinach could be contaminated in this way: Russian roulette in leafy greens.

No one knows whether this is what happened in the current outbreak. But as the FDA's microbe hunters rack up clues pointing to farms in the Salinas “Salad Bowl" Valley in California as the source of the outbreak, it is something to consider. If the problem is within the plants themselves, no amount of high-tech food-safety processing can fix things.

E. coli has been known to survive for long periods both in water and cow manure (O157:H7 is famously found in cow guts, hence the issues with contaminated hamburger). Although composting is required before applying manure as fertilizer, not even that’s a guarantee that all the e.coli will be gone. They’re tough bugs.

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It isn't hard to see how an e.coli outbreak in meat can get around: A single infected cow in a batch of hundreds of carcasses ground together into hamburger can contaminate literally tons of meat. (And since those hundreds of cows could have come from many different herds, including herds from other countries, isolating the source of the bacteria is an almost a hopeless task.)

But spinach isn’t hamburger. It isn’t chopped up into tiny pieces, stirred and crammed together. Which means that for so many people to get sick across so many states, the contamination most likely happened right in the field, affecting a fairly large growing area. And that suggests contaminated irrigation water.

Most of the crops in the Valley are irrigated by well water, which is usually pretty clean. Flooding from streams and rivers can carry e.coli, and investigators are pouring over weather records. But the problem may be with recycled or “reclaimed" water, which is used on about 12,000 acres in the region.

According to an article in the Kansas City Star, the general manager of the regional water pollution agency says the recycled water is fine. “You can't drink it but you can put it in a lake where people swim.”

Maybe. But in other states recycled water can only be used to irrigate edible crops that will later be peeled, cooked or somehow thermally treated before being eaten. Fresh spinach doesn’t qualify.

Even this more stringent policy, however, has a few microbe-size loopholes. Robert Tauxe, a medical epidemiologist specializing in food-borne illness at the CDC notes that e.coli – and Salmonella -- can coat seeds and so position themselves to infect plants as soon as they germinate. If the germs are inside, whether by seed infection or irrigation contamination, peeling is as irrelevant as washing. (NOTE: The above link is to an article,"Enteric bacteria may be leading a secret life in plants," from Infectious Disease News. It is very good, but requires a free sign-up.)

As to why animal pathogens make themselves at home in vegetables, Tauxe points out that everything from cows to people eat plants and that one of the fastest ways to get inside a host is to get eaten.

Who knew that the little green leaves you put on top of burgers to make them look slightly healthier would turn out to be the real threat? Or that Twinkies would ever one day start to look (maybe) like a good idea…