Microbes Rule the World

Microbes make up 80 percent of all biomass, says microbiologist Carl Woese. In one-fifth of a teaspoon of seawater, there are a million bacteria (and 10 million viruses), Craig Venter says, adding, “If you don’t like bacteria, you’re on the wrong planet. This is the planet of the bacteria.” That means that most of the planet’s living metabolism is microbial. When James Lovelock was trying to figure out where the gases come from that make the Earth’s atmosphere such an artifact of ...

 The Immune System Reaction and Overreaction

The body has a very ingenious and usually effective system of natural defence against parasites, called the immune system. The immune system is so complicated that it would take a whole book to explain it. Briefly, when it senses a dangerous parasite the body is mobilized to produce special cells, which are carried by the blood into battle like a kind of army, tailor-made to attack the particular parasites concerned. Usually the immune system wins, and the person recovers. After that, the imm...

 The Placenta and Toxicity

“During most of pregnancy, the placenta separating mother and fetus is only one cell thick,” Koren tells me. “But it has an array of mechanisms to help it do its job of protecting the fetus.” These subcellular tools, he explains, include tiny pumps that expel toxins before they can do any damage, immune agents that guard the placenta’s perimeter, and placental enzymes that chemically break down intruding molecules. This armamentarium does an impressive job of blocking bacteria from...