Microcosm: E. coli and the New Science of Life

E. coli’s pathways all dump their products into the same network in the knot of the bow tie. Likewise, the Internet does not have to link every computer directly to every other one, or use special codes for every kind of file it carries. In both cases this arrangement is possible only because the entire

it takes a lot of energy and material to build hi-fi polymerases. In times of stress, E. coli may not be able to afford the luxury of accurate DNA repair. Instead, it turns to the cheaper lo-fi polymerases. While they may do a sloppier job, E. coli comes out ahead on balance. Natural selection, Tenaillon proposes,

One of these viruses, known as P1, carries a gene that makes a protein called a restriction enzyme. Restriction enzymes are able to grab DNA at specific sites and slice it apart.

Animals defend against peptide-slicing enzymes by stiffening the peptides. The peptides are folded over on themselves and linked together with extra bonds. But microbes have evolved counterstrategies of their own. For example, some species secrete proteins that grab the antimicrobial peptides and prevent them from entering

Along with beta-galactosidase, E. coli makes the protein permease, which sucks lactose molecules into the microbe. When a reluctant E. coli’s lac operon switches on briefly, some of these permeases get produced. They begin pumping more lactose into the microbe, and that extra lactose can pull away more repressors.

along with its main chromosome E. coli carries extra ringlets of DNA, called plasmids.

This elegant network gives E. coli the best of all worlds. When it starts building flagella, it remains very sensitive to any sign that stress is going away. That’s because FlhDC alone is keeping the flagella-building genes switched on. But once E. coli has built a syringe and begins to pump out FlgM, the noise filters kick in. If the stress drops,

At Harvard University, for example, George Church and his colleagues have drawn up a list of 151 genes, which they think would be enough to keep an organism alive.

Once it becomes eager, E. coli will resist changing back. If the concentration of lactose drops, the microbe will still pump in lactose at a high rate, thanks to all the permease