The microbiome has been one of the major science stories in recent years. It seems that barely a week goes by that we don’t learn something new about the relationship between the human body and the millions of microbes that call it home.
But a study in the January issue of PLoS ONE suggests that the colonization may be more complete than we’ve imagined.
Despite the pervasiveness of bacteria in our bodies, biologists have long assumed that at least certain parts of it are off limits to foreign organisms. It’s been dogma for more than a century that healthy lungs are sterile—although recent research has shown the microbiome probably lives there, too. And if you were to ask physicians which compartment of the body is least likely to have resident bacteria, most would probably identify the brain: It seems improbable that the central nervous system could function with microbes jumping across the synapses.
Or maybe it could. The PLoS ONE study looked at brain tissue from 10 people, all of whom had either HIV, epilepsy, or some other control disease—and in all 10 samples they found bacterial RNA. The main type of bacteria they found is something called “a-proteobacteria,” which is surprising because it’s different from the kinds of microbes researchers have found in adjacent parts of the body like the skin and the nasal passages. This raises the possibility that a-proteobacteria is some kind of highly specialized brain bacteria performing an as-of-yet unrecognized function.
This study is the first of its kind, but if these results are confirmed, researchers will have a number of provocative questions on their hands: Why are these brain bacteria not harmful? Are they recognized by the immune system and tolerated, or do they somehow fly under the immune radar? And most importantly of all, what exactly are the bacteria doing in our brains? We consider our thoughts to be the ground zero of our identities, but perhaps even the act of thinking is a team effort.
Image of symbiotic cyanobacteria courtesy of Wikimedia Commons
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Leon Neyfakh is the staff writer for Ideas. Amanda Katz is the deputy Ideas editor. Stephen Heuser is the Ideas editor.
Guest blogger Simon Waxman is Managing Editor of Boston Review and has written for WBUR, Alternet, McSweeney's, Jacobin, and others.
Guest blogger Elizabeth Manus is a writer living in New York City. She has been a book review editor at the Boston Phoenix, and a columnist for The New York Observer and Metro.
Guest blogger Sarah Laskow is a freelance writer and editor in New York City. She edits Smithsonian's SmartNews blog and has contributed to Salon, Good, The American Prospect, Bloomberg News, and other publications.
Guest blogger Joshua Glenn is a Boston-based writer, publisher, and freelance semiotician. He was the original Brainiac blogger, and is currently editor of the blog HiLobrow, publisher of a series of Radium Age science fiction novels, and co-author/co-editor of several books, including the story collection "Significant Objects" and the kids' field guide to life "Unbored."
Guest blogger Ruth Graham is a freelance journalist in New Hampshire, and a frequent Ideas contributor. She is a former features editor for the New York Sun, and has written for publications including Slate and the Wall Street Journal.
Joshua Rothman is a graduate student and Teaching Fellow in the Harvard English department, and an Instructor in Public Policy at the Harvard Kennedy School of Government. He teaches novels and political writing.