Forbes Thinking Small and Large

How Microbes Made and Can Save Our World
1. Auflage 2025
ISBN: 978-1-83773-171-8
Verlag: Icon Books
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 288 Seiten

The environmental crisis will not be solved by battery technology. We are looking for answers in the wrong places. Life began with the hydrogenation of CO2, and this is the process we must return to in order to heal the planet. Ground-breaking ongoing research into bacterial processes means our knowledge of bacterial processes is ever-expanding, and we can harness this new knowledge to develop a parallel carbon economy using engineered bacteria for fuel, food, and materials. This would enable rewilding on a vast scale, with the small land footprint of bacterial technologies solving the current conflict in land use between farming and fuel and materials production. In this fascinating and illuminating book, Peter Forbes shines a light on this crucial technology and offers a tantalising glimpse at what is possible. To solve the big problems, sometimes you have to think small.

Peter Forbes is a science writer and journalist writing mainly on life sciences and natural history. He read chemistry and worked for the Pharmaceutical Society of Great Britain and in natural history publishing before becoming a freelance writer. He lives in London and teaches the Narrative Non-Fiction course at City St George's, University of London His first full-length non-fiction book, The Gecko's Foot: How Scientists are Taking a Leaf from Nature's Book, a ground-breaking introduction to the new field of engineering and materials solutions inspired by nature, was longlisted for the Royal Society/Aventis Prize. He followed this with Dazzled and Deceived: Mimicry and Camouflage, which won the Warwick Prize for Writing.

Autoren/Hrsg.

Forbes, Peter

Leseproben

2. TORNADO IN THE JUNKYARD

How a simple equation has been at the heart of life for around four billion years

The purpose of life is to hydrogenate carbon dioxide.

MIKE RUSSELL

So many atoms struck by every kind of blow,

Or borne by their own weight, contrived to go,

And meet in every conceivable combination,

To test the result of their congregation.

LUCRETIUS, DE RERUM NATURA

In 1977 researchers on the deep-sea submersible vessel Alvin discovered hot upwelling mineral vents – black smokers – in the deep Pacific Ocean, off the coast of California. It became a hot news story because of the very strange, previously unknown creatures, especially giant tube worms up to three metres long, that lived on the mineral-rich effluents.

There was nothing remotely primal about these creatures themselves, but the interest of biologists and biochemists was piqued by the constant flow of hot, chemically rich effluents, which suggested that vents like this this might have been life’s birthplace.

The energetic chemistry discovered in the black smokers bore some resemblance to the energy metabolism of life today, especially the presence of iron-sulphur (FeS) clusters. These clusters lie at the heart of many of the nanomachines that perform life’s key functions but, after investigation, the black smokers were ruled out as life’s originators: they were too hot and the chemistry was all wrong.

Fast-forward 23 years. Alvin was still in business and its mothership the Atlantis was scanning the sea floor near the mid-Atlantic Ridge when ghostly whitish towers were seen rising from the sea floor. The towers reached 60 metres high and were composed of limestone. Alvin was launched to investigate further.

For the discoverers – research scientists Deborah S. Kelley, Jeffrey Karson and Gretchen Früh-Green at the School of Oceanography, University of Washington, Seattle – the discovery was as profound and surprising as that of the first smokers. This new venting system, called Lost City, was unlike any place ever previously visited. Investigation of the site is changing our views not only about the conditions under which life can thrive on our planet, but on others as well.

But for one scientist, the geochemist Mike Russell – a professor of geology at Glasgow University before becoming a researcher at NASA – the find didn’t change his views but confirmed them. In a series of papers beginning in 1988, he had predicted the existence of just such structures: hydrothermal vents, alkaline and much cooler than the black smokers. He hypothesised that in these vents, through a well-known geological process called serpentinisation, a common rock, olivine, would have reacted with water under pressure beneath the ocean to produce hydrogen; this could then have reacted with dissolved CO2 in the ocean waters, creating the precursor chemicals of life. In fact, Russell went so far as to make that claim: ‘The purpose of life is to hydrogenate carbon dioxide’. The very best science is done like this: a prediction – often seemingly improbable – followed by a clinching discovery.

Russell’s insight has led to the most convincing account, backed up by substantial laboratory evidence, for the mechanism of life’s origin. What was once wishful thinking for Darwin – ‘But if (and oh what a big if) we could conceive in some warm little pond with all sorts of ammonia and phosphoric salts, light, heat, electricity etcetera present, that a protein compound was chemically formed, ready to undergo still more complex changes’ – is now an experimental science.

Calcium carbonate chimneys in the Lost City hydrothermal vent system at the Mid-Atlantic Ridge.

I can trace the genesis of my interest in this topic back to Joseph Bronowski’s TV blockbuster and book The Ascent of Man in the 1960s. It had an appealing aura, clothing science in a suave, wise voice that made it the equal of the arts. But, specifically, it was a topic I first encountered in Bronowski’s programme, the primitive origin of life experiment of Harold Urey and Stanley Miller conducted at the University of Chicago in 1952, that piqued a lifelong interest.

The Miller–Urey experiment caught people’s imagination because it was the beginning of experimentation on the subject. But, of course, it still had to start with a hypothesis. They assumed that on the early earth the atmosphere would have contained water vapour, methane, ammonia, hydrogen, and that the world then was a very violent place with bombardment from space. They also assumed in this hellish climate (the period is named the Hadean) that there would be heavy and frequent lightning strikes with the potential to trigger the synthesis of simple organic chemicals.

So they circulated these gases through a series of flasks and administered electric shocks to simulate the lightning. Miller reported that ‘the water in the flask became noticeably pink after the first day, and by the end of the week the solution was deep red and turbid’. The simple amino acids glycine, a-alanine and ß-alanine were definitively identified in the product.

This broke a spell, showing that the synthesis of some of the essential building blocks of life was possible under real-world conditions. But this was a false dawn. Although useful chemicals were found in Miller and Urey’s flask, on the early earth they would have been instantly dissipated, just as they would in Darwin’s scenario. Life processes require a watery environment but water flows where it wants, and nothing can be confined in a pond, let alone an ocean.

A more realistic scenario required tiny mineral compartments that could harbour the early prebiotic chemicals and a ceaseless flow of the right gases at a good temperature to encourage reactions that would reliably run for at least thousands of years. You’ve probably realised that we have now rejoined the undersea vents story because they have both these features.

But there are still two vital factors missing in the scenario I’ve painted. Firstly, where is the energy going to come from? All living things require a constant supply of energy and the process was never going to start without a steady source of it. Miller and Urey were not considering the energy needed to create and maintain organic synthesis. Lightning was their putative spark of life, but that is hardly the constant source needed to sustain it. Life cannot be created by a bolt from the blue, however appealing that Frankensteinian idea may be, although life’s ‘secret’ is, in a sense, electrical, as we’ll see. And secondly, if the purpose of life is to hydrogenate carbon dioxide, as Mike Russell put it, nature has perversely made that quite hard to do. In all living things today, the reactions of life are catalysed by protein enzymes honed by billions of years of evolution. In the popular imagination, enzymes mean just a slightly better washing powder, but in fact they run the whole shooting match of life’s metabolism. Some primal equivalent of these was necessary in the early stages that led to life.

As for the energy needed, a revolutionary hypothesis, made nine years after the Miller–Urey experiment, led to an understanding of the source of all life’s energy. This was the work, in 1961, of the maverick English scientist Peter Mitchell (1920–1992; Nobel Prize 1978) and his co-worker Jennifer Moyle. Despite Mitchell’s Nobel Prize, these two remain unknown to the general public and relatively uncelebrated. Yet Mitchell and Moyle have as much claim as Watson and Crick to be discoverers of the ‘secret of life’. Because there isn’t just one secret of life: there are many.

Mitchell, a notably individual scientist, was one of the very few who were rich before they won the Nobel Prize, his uncle’s fortune (he owned the building contractors Wimpey) allowing him to indulge his passion for fast cars. Retiring from his academic post at Edinburgh University in 1963 through ill health, he set up a private research unit, the Glynn Institute, with co-researcher Jennifer Moyle, in a Regency-fronted mansion in Bodmin, Cornwall, half an hour away from where that other, much better known maverick freelance scientist James Lovelock was later to set up home and laboratory.

Mitchell published most of his work eccentrically as Glynn Institute papers (although his most important paper was published in the leading journal Nature in 1961) and was at odds with the biological establishment for much of the time on nature’s energy-generating process. The conflict was known as the Ox-Phos Wars (oxidative phosphorylation being the technical name for the process that uses oxygen to generate the energy that powers life). The dispute went on for more than a decade but, eventually, experiment – mostly done by Jennifer Moyle – confirmed the theory, known as the chemiosmotic theory, now one of the pillars of biology.

Mitchell believed that the energy of life arises from a concentration gradient of hydrogen ions across the membrane of the cell, generating an electrical potential that can do chemical work. This occurs at the boundary between bacteria and their environment, and, in organisms with nucleated cells, including all the animals and plants, in specialised organs, the mitochondria, which are life’s energy packs (and much more, as we’ll see in the next chapter).

The hydrothermal vent theory, hatched by Mike Russell in the late-1980s,...