The Loh Down On Science

Here's what happens when quality control runs amok

Black symbols and arrows indicate plasmid's toxin/antitoxin pairs. Image credit: Kofpmann & Hess, J. of Biol. Chem.

We humans are obsessive about killing bacteria. But can bacteria themselves have a death wish?

This is Sandra Tsing Loh with the Loh Down on Science.

Meet Synechocystis. This bacterium contains a small extra fragment of DNA called a plasmid.   The plasmid contains instructions for simultaneously making both a toxin and an antitoxin.  And once made, the toxin is much more stable than the antitoxin. Uh oh­—sounds like trouble!

When Synechocystis reproduces, the original bacterium duplicates its DNA, then splits into two.   Now, both cells contain some leftover toxin.   So if, during division, either cell lost its antitoxin-producing plasmid, the old toxin is still very present, and very deadly.  

Because other important genes are on the plasmid, this ensures that future generations of bacteria are correctly formed and tough enough to survive. 

What's more? Synechocystis produces not one but seven toxin/antitoxin pairs.   So if six of them fail, there’s still that last one to make sure the defective cell bites it.  

And we think we're so superior with our hand sanitizer. Please.

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Thursday, from 2-3 p.m. on the LDOS blog: Sandra chats with author Po Bronson about his book NurtureShock.

The Loh Down on Science is produced by LDOS Media Lab, with 89.3 KPCC. And made possible by the generous support of the Gordon and Betty Moore Foundation.

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