Invisible Friends How Microbes Shape our Lives and the World around Us

As the invisible glue that holds the world together, microbes might well be some of the most underappreciated life forms on our planet. Invisible Friends discusses the many beneficial and vital roles microbes play in our lives. This is an enthusiastic and hopeful romp through microbiology that encourages readers to rethink their relationship with nature and see themselves as embedded in it. Keep your critical thinking caps at hand though, as the book gets starry-eyed in places.

Microbial ecologist Jake M. Robinson is a man on a mission: to challenge our negative perception of microbes and to encourage people to rethink their place in nature by showing how, when it comes down to it, microbes run the show. As used here, microbes encompass not just bacteria but also fungi, algae, viruses, archaea, and protozoa. I expected coverage of the microbiome, and Robinson indeed discusses the ecosystem of invisible organisms that live in and on us. One chapter in particular delves into the microbiota-gut-brain axis, i.e. how our diet affects our gut flora, how our gut flora communicates with our brains, and how this whole ensemble influences our physical and mental health. Now, this topic has already been thoroughly explored by other popular science writers. Fortunately, Robinson considers many other topics and does so in a chatty and conversational tone. Many of these I found both novel and eye-opening.

For example, I was familiar with one formulation of the hygiene hypothesis: the idea that we have weakened our immune system through the constant indoor use of household cleaners and disinfectants. An interview with immunologist Graham Rook discusses how this hypothesis morphed over time and why he thinks it does not stack up. He instead proposes that our indoor environments are lacking the so-called "old friends" found outdoors that humans evolved in symbiosis with. In their absence, opportunistic bacteria can more easily overwhelm us. Meanwhile, growing up without sufficient exposure to outdoor environments does not properly train our immune system, leading to an increased risk of allergies or even autoimmune diseases as an adult. Another intriguing idea is that microbes impact our behaviour and decisions. Robinson has argued in print that our microbiome might influence our decisions to spend time in certain environments favourable to these microbes, while some of our impulsive behaviours could be driven by "our microbial puppet masters" (p. 98). Or what about the prospects of forensic microbiology? Microbes left behind at a crime scene could be linked to specific places and people, potentially identifying perpetrators, or revealing the cause of death. He admits more research is needed to ground truth these methods, but I would argue that the field of forensic entomology offers a noteworthy precedent, while two forensic botanists have previously written about their use of microscopic plant remains to solve crimes.

However, other topics fall into the "sure, but" category where I find Robinson is not critical enough and becomes optimistic to the point of being starry-eyed. He is enthusiastic about the idea of getting people outdoors and in contact with health-promoting microbes through e.g. community gardens. Sure, I do not want to downplay the benefits, but he does not mention that urban agriculture has been criticized for in practice not producing much food and being a boutique hobby for well-off urbanites.

Robinson furthermore visits a farm practising regenerative agriculture which puts soil health, and thus soil microbes, above all else. Sure, conventional agriculture does much environmental harm in the name of feeding people, but he glosses over important details. George Monbiot's book Regenesis critically asked whether this kind of farming has comparable yields and highlighted there is little land left that we can still bring under cultivation. He also does not challenge the farmer who claims to grow "delicious chemical-free vegetables" and use "all-natural matter, soil and compost" (p. 127). This is surprising; as a microbiologist, Robinson understands that food is nothing but (bio)chemistry. I am sure this farmer means he avoids synthetic pesticides, but this kind of sloppy language has the appeal-to-nature fallacy written all over it. One notable gaffe is that Robinson supports the idea that modern food is less nutritious by claiming (p. 126) that today's apples contain 26 times less iron than those in 1940 – only to then in an endnote (p. 252) immediately add that he could not verify this claim. Next to this idea having been questioned, throwing in unverified claims is just bad science writing – the risk of readers missing that asterisk and the book perpetuating potential misinformation is high. No need to add to the noise already out there.

Fortunately, this seems to be an isolated incident. Robinson thinks more critically when discussing bio-integrated design, i.e. the use of microbes in architecture. Could algae be used to create buildings that can purify the air? Possibly, but "ideally, we should be focusing on reducing the pollution at the source" (p. 156). Many design firms hype the idea of e.g. making bricks out of fungi, but Robinson does not comment on whether such solutions can be scaled up beyond prototypes. Plus, if you mention biodegradable buildings, why overlook traditional practices such as mud or wattle and daub?

Somewhere on page 165, Robinson jokes about churning out conference posters with new research ideas in the hopes of attracting a rich benefactor. I think this explains some of my criticism: here is someone of boundless enthusiasm constantly throwing out new ideas. Not all of these will necessarily stick, but, arguably, we need creative minds to inspire new directions in research.

Finally, it is worth mentioning Robinson has a progressive outlook. He discusses issues around social equity: poor people and minorities frequently have less easy access to healthy, biodiverse environments. He highlights where indigenous cultures have held ideas that modern science is now verifying and is especially keen to draw lessons from their holistic worldviews that see humans as an integrated part of nature. Research on the microbiome and its link to human health and well-being resonates with such ideas. His last chapter considers how we can rekindle our relationship with nature through e.g. mindful outdoor activities such as forest bathing – while being exposed to a healthy dose of outdoor microbes.

Overall then, Invisible Friends is interesting, optimistic, and hopeful, but also speculative in places. Does it succeed in making you reconsider your place in nature? Sure, but readers are advised to keep their critical thinking caps on.