I Contain Multitudes: The Microbes Within Us and a Grander View of Life

by Ed Yong

Given all the important roles that bacteria play in our bodies, it should be possible to improve our health by swallowing or applying the right microbes. It’s just that the strains in current use may not be the right ones. They make up just a tiny fraction of the microbes that live with us, and their abilities represent a thin slice of what the microbiome is fully capable of. We met more suitable microbes in earlier chapters. There’s the mucus-loving bacterium, Akkermansia muciniphila, whose presence correlates with a lower risk of obesity and malnutrition. There’s Bacteroides fragilis, which stokes the anti-inflammatory side of the immune system. There’s Faecalibacterium prausnitzii, another anti-inflammatory bug, which is conspicuously rare in the guts of people with IBD, and whose arrival can reverse the symptoms of that disease in mice. These microbes could be part of the probiotics of the future. Their abilities are relevant and impressive. They are well adapted to our bodies. Some are already abundant – in healthy adults, one in every twenty gut bacteria is F. prausnitzii. These are not D-listers of the human microbiome like Lactobacillus; they are the stars of the gut. They won’t be shy about colonising it.20 Then again, effective colonisation carries greater risk along with greater reward. So far, probiotics have enjoyed a mostly clean safety record,21 but that might well be because they’re poor at maintaining a foothold in the body. What would happen if more commo...