Sunday, June 5, 2011

E. coli and humans: a love/hate relationship

It's all over the news again.  Another new strain.  Another food scare.  This time, it's in bean sprouts.  Is there anything left that I can safely eat anymore?  This bug is a zombie.  And each time it comes back, it seems to be more deadly than before.  Why doesn't science just get rid of it?

Well, we can't.  And furthermore, we won't.

For one thing, you need it.  E. coli lives happily in your intestine and helps you digest your food.  When a bad strain of E. coli invades, one of the harmful things it does in your poor body is wipe out the good E. coli, along with many other beneficial species of bacteria that live there.  Hardly seems fair, eh?  But such is the law of natural selection.

Furthermore, science loves E. coli.  Indeed, the ratio of E. coli bacteria to humans within any molecular biology lab is generally about ten billion to one.  As I type this, there are probably twenty liters or so of stinky E. coli being cultured in my lab.  It's the safe kind.  We could bathe in it (not that I would...) with no ill effects. 

Why is it there?  Well, we know how to exploit the very nature of this bug that can make it so harmful: it replicates like crazy.  We use this fact to our advantage and use E. coli to clone any gene we are interested it. 

It's quite simple, really.  We can pop a gene into an E. coli bacterium (this is frequently done by electrocuting the bug!) and the next morning, an entire population of clones from that bug will have our DNA of interest inside them.  We crack those bugs open and pull out our gene, which they have been so kind as to replicate for us in droves overnight.  We can then chop that gene up and splice it into other genes.  And this is molecular cloning at its most basic.

So please don't expect these little guys to go away any time soon.  Just wash your bean sprouts.

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