The following is an excerpt from Wild Fermentation: The Flavor, Nutrition, and Craft of Live-Culture Foods  by Sandor Katz . It has been adapted for the Web. Our culture is terrified of germs and obsessed with hygiene. The more we glean about disease-causing viruses, bacteria, and other microorganisms, the more we fear exposure to all forms of microscopic life. Every new sensationalized killer microbe gives us more reason to defend ourselves with vigilance. Nothing illustrates this more vividly than the sudden appearance, everywhere in the United States, of antibacterial soap. Twenty years ago, mass marketing of antibacterial soap was but a glimmer in some pharmaceutical executive’s eye. It has quickly become the standard hand-washing hygiene product. Are fewer people getting sick as a result? “There’s no evidence that they do any good and there’s reason to suspect that they could contribute to a problem by helping to create antibiotic-resistant bacteria,” says Dr. Myron Genel, chair of the American Medical Association’s Council on Scientific Affairs. Antibacterial soap is just another exploitative and potentially dangerous product being sold by preying on people’s fears. The antibacterial compounds in these soaps, most commonly triclosan, kill the more susceptible bacteria but not the heartier ones. “These resistant microbes may include bacteria . . . that were unable to gain a foothold previously and are now able to thrive thanks to the destruction of competing microbes,” says Dr. Stuart Levy, director of the Tufts University Center for Adaptation Genetics and Drug Resistance. Your skin, your orifices, and the surfaces of your home are all covered with microorganisms that help protect you (and themselves) from potentially harmful organisms that you both encounter. Constantly assaulting the bacteria on, in, and around you with antibacterial compounds weakens one line of defense your body uses against disease organisms. Microorganisms not only protect us by competing with potentially dangerous organisms, they teach the immune system how to function. “The immune system organizes itself through experience, just like the brain,” says Dr. Irun R. Cohen of the Weizmann Institute of Science in Israel. A growing number of researchers are finding evidence to support what is known as “the hygiene hypothesis,” which attributes the dramatic rise in prevalence of asthma and other allergies to lack of exposure to diverse microorganisms found in soil and untreated water. “The cleaner we live . . . the more likely we’ll get asthma and allergies,” states Dr. David Rosenstreich, director of Allergy and Immunology at the Albert Einstein School of Medicine in New York. Paranoia about germs has been magnified by the recent anthrax terror and fears of biological warfare. According to the December 2001 newsletter of Household and Personal Products on the Internet, “A widespread fear of disease—specifically anthrax bacteria—has caused consumers to take a more serious look at cleansing. . . . Antibacterial cleansers are expected to spike in sales.” Well-informed hygiene is very important, but it is impossible to avoid exposure to microbes. They are everywhere. A 70s made-for- TV movie called The Boy in the Plastic Bubble dramatized the tragic saga of a young man born with an immune disorder who could only survive in a germ-free environment. The boy, portrayed by John Travolta en route to superstardom, lived in a hermetically sealed, sterilized room and could only interact with other people through protective barriers. He periodically ventured out of his room in a spacesuit-like outfit. He grew so lonely and sad in his sterile cage that he chose to leave it and live normally for the brief time before the inevitable pathogenic organism killed him. This is a pop culture parable of the impossibility and undesirability of sequestering oneself from the biological risks of being alive. Much of Western chemical medicine aims to eradicate pathogenic organisms. In the case of my AIDS drugs, the treatment strategy is called “highly active anti-retroviral therapy.” Having benefited from the miracles of high-tech pharmaceuticals, I’m in no position to argue against the value of this approach. I firmly believe, however, that microbial warfare is not a sustainable practice. “Bacteria are not germs but the germinators—and fabric—of all life on Earth,” writes Stephen Harrod Buhner in The Lost Language of Plants. “In declaring war on them we declared war on the underlying living structure of the planet—on all life-forms we can see—on ourselves.” Health and homeostasis require that humans coexist with microorganisms. Bacteria-counting scientists have quantified this simple fact, estimating that each person’s body is host to a bacterial population in excess of 100 trillion, and noting that “the interactions of these colonizing microbes with the host are nothing if not complex.” Humans and all other forms of life evolved from and with these organisms, and we cannot live without them. “Nature appears to maximize mutual cooperation and mutual coordination of goals,” wrote ethnobotanist Terence McKenna. “To be indispensable to the organisms with which one shares an environment—that is the strategy that ensures successful breeding and continued survival.” The study of symbiogenesis views evolutionary innovation as a consequence of symbiosis, tracing the source of all life to prokaryotes, which are cells distinguished by the absence of nuclear membranes. Bacteria are prokaryotes. Their genetic material is free-floating in the cell. “Genes from the fluid medium, from other bacteria, from viruses, or from elsewhere enter bacterial cells on their own,” write biologists Lynn Margulis and Karlene V. Schwartz. By incorporating DNA from their environment into themselves, prokaryotes assimilate genetic traits. They evolved first into eukaryotes (cells with nuclear membranes) and eventually into complex organisms such as ourselves. But they never left their progeny; they are with us always. “Prokaryotes are the master engineers of our complexity,” explains my excited scientist friend Joel Kimmons, recent recipient of a Ph.D. in nutrition from the University of California. Inside our bodies, most dramatically in the gut, prokaryotes absorb genetic information that informs our function as organisms; they are an integral part of our sentient experience. “We eat and thus we know,” says Joel. Humans are in mutually beneficial and mutually dependent relationships with these and many different microbes. We are symbiotic, inextricably woven together, in a complex pattern far beyond our capacity to comprehend completely.