Biologist Rob Dunn, an applied ecology professor at North Carolina State University and the author of several books, including “Never Home Alone: From Microbes to Millipedes, Camel Crickets, and Honeybees, the Natural History of Where We Live,” talks with us about his studies into sourdough starters, the impact of fast food and industrial farming on our gut’s “garden,” and the transformative nature of embracing global networks and communication.