Microcosm: E. coli and the New Science of Life

Genes do not work in isolation. They work in circuits. Over the next few weeks, Jacob tried to

E. coli’s bacteriophages were not all alike. Some could infect certain E. coli strains but not others. By triggering mutations in the viruses, the scientists could cause the viruses to infect new strains. The ability to infect E. coli passed down from virus to virus.

It is only through the switching on and off of genes that our cells can behave differently from one another,

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.

Within the human gut alone there are about a thousand species of viruses. As viruses pick up host genes and insert them in other hosts, they create an evolutionary matrix through which DNA can shuttle from species to species.

Bernhard Palsson, a biologist at the University of California, San Diego, has overseen the construction of a model of E. coli’s metabolism.

make neither the amino acid methionine nor biotin, a B vitamin. The other strain he picked couldn’t make the amino acids threonine and proline. Lederberg put the bacteria in a broth he stocked with all four compounds so that the mutant microbes could grow and multiply. They mingled in the broth for a few weeks, with plenty of opportunity for hypoth

Those two types turned out to be ecological partners. The large colonies are inhabited by microbes that do a better job than their ancestors at feeding on glucose. One of the waste products they give off is acetate. E. coli can survive on acetate, although it grows more slowly on

Hypermutation has an obvious risk: along with a beneficial mutation, it can also cause many harmful ones. Susan Rosenberg of Baylor College of Medicine and her colleagues argue that E. coli minimizes this risk by spreading it across an entire colony.

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.