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Kindle Notes & Highlights
by
Ed Yong
Read between
May 11 - May 28, 2021
there are more bacteria in your gut than there are stars in our galaxy.3
The latest estimates suggest that we have around 30 trillion human cells and 39 trillion microbial ones –
There are fewer than 100 species of bacteria that cause infectious diseases in humans;8
Your cells carry between 20,000 and 25,000 genes, but it is estimated that the microbes inside you wield around 500 times more.9
Islands are where you go if you want to find life at its most outlandish, gaudy, and superlative.
Speaking of palms, your right hand shares just a sixth of its microbial species with your left hand.
Put simply, the bacteria on your forearm are more similar to those on my forearm than to those in your mouth.
almost three-quarters of a newborn’s strains can be traced directly back to its mother.
When a human mother breastfeeds her child, she isn’t just feeding it; she is also feeding the child its first microbes, and ensuring that the right pioneers settle inside its gut. Knight wonders if the same applies to meerkats. Do the abandoned pups start their lives with the wrong microbes because they don’t get mother’s milk? Do those early changes affect their health in later life?
If one partner benefited at the expense of the other, it was a parasite (or a pathogen if it caused disease). If it benefited without affecting its host, it was a commensal. If it benefited its host, it was a mutualist. All these styles of coexistence fell under the rubric of symbiosis.
We see it as a defence force that discriminates self (our own cells) from non-self (microbes and everything else), and eradicates the latter. But now we see that microbes craft and tune our immune system in the first place!
The immune system isn’t just a means of controlling microbes. It is at least partly controlled by microbes.
He collected many samples of stomach acid, and he sometimes dangled food through the open hole to watch it being digested in real time. The experiments continued until 1833, after which the men finally parted ways. St Martin returned to Quebec, where he died as a farmer at the age of 78. Beaumont became known as the Father of Gastric Physiology.39
Psychiatric problems and digestive problems often go hand in hand. Biologists speak of a “gut–brain axis” – a two-way line of communication between the gut and the brain.
Ever wonder why two people can walk through a midge-filled forest and one emerge with dozens of welts while the other just has a smile? Your microbes are part of the answer.11
Symbiosis is conflict – conflict that can never be totally resolved.”
Mucus is made from giant molecules called mucins, each consisting of a central protein backbone with thousands of sugar molecules branching off it. These sugars allow individual mucins to become entangled, forming a dense, nearly impenetrable thicket
bacteriophages – literally, “eaters of bacteria”
The immune system’s main function is to manage our relationships with our resident microbes. It’s more about balance and good management than defence and destruction.
why babies are vulnerable to infections for their first six months of life.30 It’s not because their immune system is immature, as is commonly believed: it’s because it is deliberately stifled to give microbes a free-for-all window during which they can establish themselves.
Gut microbes also partly explain the remarkable success of gastric bypass surgery: a radical operation that reduces the stomach to an egg-sized pouch and connects it directly to the small intestine. After this procedure, people tend to lose dozens of kilograms, a fact typically accredited to their shrunken stomachs. But the operation also restructures the gut microbiome, increasing the numbers of various species, including Akkermansia. And if you transplant these restructured communities into germ-free mice, those rodents will also lose weight.
There have got to be a few major factors in our modern lifestyle that explain a large proportion of this. There aren’t going to be 30 different things that we’re doing that cause 30 different diseases. My guess is that there are five, or three, or maybe even one thing that explains 90 per cent of 90 per cent of these diseases. It seems that there’s got to be a single unifying cause.”
When Susan Lynch hoovered up the dust of 16 homes, she found that those without furry pets were “microbial deserts”. Those with cats were far richer in microbes, and those with dogs were richer still.23 It turned out that man’s best friend is a chauffeur for man’s old friends.
“If you pass small stools, you have big hospitals.”26
But antibiotics are shock-and-awe weapons. They kill the bacteria we want as well as those we don’t – an approach that’s like nuking a city to deal with a rat.
Our planet has entered the Anthropocene – a new geological epoch when humanity’s influence is causing global climate change, the loss of wild spaces, and a drastic decline in the richness of life.
This isolation ends when we pass through the birth canal and encounter vaginal bacteria. These are our first colonisers – the pioneers of the empty ecosystems inside us. Much like a Japanese stinkbug, we emerge into the world slathered in mum’s microbes.
Contact breeds conformity. Sometimes, the long waltz involves hip-checks.
By changing the flies’ diet, Dodd had somehow altered their sexual preferences.
after just two generations, the flies were more attracted to individuals that were reared on the same diet. And if the insects swallowed a dose of antibiotics and lost their microbes, they also lost their sexual biases.27
Simeon Burt Wolbach will forever be immortalised in Wolbachia. Louis Pasteur lives on as Pasteurella. You’ve probably never heard of the obscure American veterinarian Daniel Elmer Salmon, but you’ll probably know of his namesake Salmonella. Which name to graft onto the aphid’s symbiont? There was never really any choice. She called it Buchnera.3
At a depth of 2,400 metres, about a mile and a half straight down, the team found the vents they had predicted, but also something they had not – life, in extreme abundance.
For Riftia’s bacteria, that’s sulphur, or rather the sulphides that spew out of the vents. The bacteria oxidise these chemicals and use the liberated energy to fix carbon. This is chemosynthesis: making your own food using chemical energy instead of light or solar energy. And rather than producing oxygen as a waste product, as photosynthetic plants do, these chemosynthesising bacteria churn out pure sulphur. Hence the yellow crystals in Riftia’s trophosome.
By internalising those bacteria, the animals gained a ticket to the Hadean depths from which all life emerged.
The plant-eating herbivores typically had the highest diversity of bacteria. The meat-eating carnivores had the lowest. The omnivores, with their broad diets, were in the middle.
To eat a diet of plants, animals need microbes in both great diversity and great abundance.
But the spider mite is impervious. One of its genes can make an enzyme that converts hydrogen cyanide into a harmless chemical. The same gene is present in the caterpillars of various butterflies and moths; they, too, shrug at cyanide. Neither the spider mite nor the caterpillars invented the cyanide-busting gene for themselves, nor did they inherit it from the common ancestor. The gene came from bacteria.34
These jumps are all the more impressive because we humans, with all our intelligence and technology, positively struggle to create new antibiotics. So flummoxed are we that we haven’t discovered any new types for decades. But simple animals like ticks and sea anemones can make their own, instantly achieving what we need many rounds of research and development to do – all through horizontal gene transfer.
“The future will be à la carte.”
Every person aerosolises around 37 million bacteria per hour.
sterility is a curse not a goal, and a diverse ecosystem is better than an impoverished one.
