Microcosm: E. coli and the New Science of Life

You may begin to imagine its genome as an instruction manual for an exquisite piece of nanotechnology crafted by some alien civilization.

a pair of membranes, one nested in the other. The membranes block big molecules from entering E. coli and keep the microbe’s molecules from getting out.

Except for the proteins it needs to defend against stomach acid, E. coli simply stops making proteins altogether.

When scientists map the pathways that a carbon atom can take through E. coli’s metabolism, the picture they see looks like a bow tie. On one side of the bow tie are the chemical reactions that draw in food and break it down. These reactions follow each other along simple pathways, a fan of incoming arrows. Eventually the arrows all converge on the

radically different ways even though they were all genetically identical.

Genes can shuttle between bacteria by many routes. Plasmids deliver some of them, but viruses deliver them as well. They accidentally incorporate

controlled by the switch that turned on the original gene.

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,

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

host genes into their own genome, which the viruses then carry to new hosts that they infect. Sometimes bacteria simply slurp up the DNA that spills out when other microbes die.