It's a book extract: "Excerpted from The Hidden Half of Nature: The Microbial Roots of Life and Health by David R. Montgomery and Anne Biklé. Copyright © 2016 by David R. Montgomery and Anne Biklé. With permission of the publisher, W.W. Norton & Company, Inc. All rights reserved."

Based on that section, I would look for an extract from The Good Gut (1) instead. It leans more towards science and less towards popularization....

(1) http://www.amazon.com/The-Good-Gut-Control-Long-term-ebook/d...