For three billion years bacteria were the sole living inhabitants on Earth. Today humans host around 100 trillion bacterial cells, outnumbering human cells 10 to one. The three pounds of bacteria that we contain forms what is called the microbiome, the ecosystem of microorganisms on which we all depend. But what if this elaborate community of organisms was threatened? Today’s guest Dr. Martin Blaser spells out exactly that scenario in his new book Missing Microbes: How the Overuse of Antibiotics is Fueling Our Modern Plagues. Dr. Blaser is director of the Human Microbiome Program at New York University, former president of the Infectious Diseases Society of America and is the cofounder of Bellevue Literary Review. His work has appeared in The New Yorker, Nature, The New York Times, The Washington Post and the Wall Street Journal and he has studied the role of bacteria in human disease now for more than 30 years.