MICROCOSM

The author explains why that bug that lives in your intestine has been a bonanza for biologists.

Though the toxic strain of E. coli is the one that makes news—usually thanks to contaminated food—many strains are weak, harmless and/or helpful, notes seasoned science writer Zimmer (Smithsonian Intimate Guide to Human Origins, 2005, etc.). Newborns are infected with E. coli from birth, and after settling in the gut, the bacteria forms an ecosystem with other bugs that helps us digest foods, make useful proteins and fend off pathogens. The bug’s main claim to fame, however, is the debt owed by genetics and the biotech industry to E. coli and the viruses (bacteriophages) that infect it. Ingenious experiments by a constellation of Nobelists including Salvador Luria, Max Delbrück and Joshua Lederberg established the startling fact that bacteria have sex; that’s how they exchange genes and spread useful mutations such as resistance to antibiotics. The phages that infect E. coli can contribute their genes as well. Zimmer goes on at length to describe how E. coli adapts to life’s vicissitudes. Too hot an environment? Make heat-shock proteins. Only lactose and not glucose for food? Switch on genes that make lactose-digesting enzymes. Need to get away fast? Grow flagella. And more. In somewhat confusing order, the author piles on descriptions and digressions into feedback circuitry, bacterial sensors, bacterial and human evolution, specialization of bacteria within colonies and cooperation across species in aggregates of bacteria in “biofilms.” He explains how E. coli became the darling of the biotech industry when geneticists realized that they could splice human genes into the bacteria and generate useful products like insulin. He rehashes the controversies over recombinant DNA and philosophizes about current concerns regarding genetically modified crops and cross-species hybridization. He ends with an excursion into astrobiology and what forms life might take Out There.

Provides plenty of gee-whiz moments, but Zimmer needn’t have used every single index card from his formidable research.