The message is always in the mucus
Modern monsters can rarely do without slime and slobber, be it on screen in movies like Alien or in stories like the ones H.P. Lovecraft wrote. In a sense, slime makes humans biological creatures, yet becomes the line of demarcation between us and the Other. Is this because slime as a phenomenon is slippery to grasp but nonetheless elicits strong emotions? Physically speaking, it can be defined and therefore contained. Slime is an extremely aqueous and viscously fluid hydrogel, which also bears the properties of a solid under certain conditions. Biological slimes are so flexible that they can easily adapt as required. Scientists are trying to copy or emulate these sophisticated structures for applications like soft robots, smart wound dressings or tailor-made glues, but often come unstuck when attempting to unravel their biological complexity.
Yet the first steps have been taken and, in the future, it may be possible to imitate even more specialized slimes, which serve as the adhesives, lubricants and selective barriers vital to microbes, animals and plants. There is probably no single living creature that does not depend on slime in some way. Most organisms use slime for a number of functions, be it as a structural material, as jellyfish do; for propagation, as plants do; to catch prey, as frogs do; for defense, like the hagfish; or for movement, like snails. The ubiquity of slime is little recognized, because many biological hydrogels hide behind pseudonyms like “mucilage,” “mesoglea,” “marine snow,” and, of course, “mucus,” which barely give an inkling of their true and common nature.
Since many of these biological hydrogels are secreted outwards, they work beyond the single organism. Even in the natural environment they are invisible cement, holding different ecosystems together, from desert to coastline to marine habitats, primarily at the interfaces where water, land, and air meet. Slime is a central cog in the world we live in and even slight changes could have global effects. The looming reality of climate change and other environmental crises like the loss of ecosystems and biodiversity threatens hydrogel-based relationships and processes. However, a new equilibrium in a warmer world might also favor slime in some habitats, allowing it to return to dominance. It would be a step back into an early era of evolution, a new era of slime.
Slime and evolution: spanning billions of years. Slime and the planet: gluing global cycles and processes together. Slime and life: a foundation to us and all organisms. Slime in the lab: technology going soft. Slime on paper: linking nature and art. Slime and monstrosity: a trigger of disgust. Little by little, enough pieces of the puzzle came together: slime is neither an accident nor an exceptional presence in the world. It is an omnipresent rule.
Dr. Jekyll and Mrs. Slime
Patricia Highsmith’s great love of snails began as a young woman, when she came upon two brown-striped specimens locked in “a bizarre embrace” at a New York fish market and took them home. Her fascination for the creatures’ mating ritual inspired two of her protagonists. The first was Victor Van Allen in Deep Water (1957), who observed an intimacy in the animals which was lacking in his destructive marriage. In her short story “The Snail Watcher”, however, the ominous beginning hints where the short story is going: “When Mr Peter Knoppert began to make a hobby of snailwatching, he had no idea that his handful of specimens would become hundreds in no time.” Spoiler alert: they don’t stop till they overwhelm their host in a “glutinous river”.
Highsmith herself was unafraid of slimy armies, keeping hundreds of snails as pets and taking them in a salad-filled handbag to dinner parties for company. When she moved to France and wasn’t allowed to bring foreign escargots legally into the country, she even resorted to smuggling. In several trips she brought the snails across the border, stowing a few of them under her bosom each time. A surprising degree of care, perhaps, for a woman with an abrasive personality, but maybe less surprising for an author who felt drawn to the grotesque, the gruesome and the macabre.
Organism
There is probably no slime-free life form in existence and maybe there never was. Human beings are not special or different in this regard; we’re simply the best-researched multicellular organism when it comes to slime. Our bodies are equipped with four different hydrogel or gel-like systems, so that invading pathogens encounter a new slimy barrier at every level. These are highly specialized gels, adapted to particular needs with a multitude of functions, and they cooperate with the immune system. The extensive slime barriers which coat our internal interfaces, such as the digestive tract, also interact with billions of resident microbes, which live inside us and contribute to our well-being. This symbiotic community is so tightly interlinked that it’s hardly possible to view animals and plants as individuals. Each multicellular organism forms what is known as a holobiont, the assemblage of a host and the microbes living in and on it, and slime makes that coexistence just so much more peaceful.
Gaia and the Gel
Microbes are the foundation and engineers of global ecosystems, as in the depth of the planet so on its surface, where no single habitat has been found free of them so far, from the hottest deserts to the Arctic and darkness of the deep sea. They have had billions of years to adapt to these extreme places and paved the way for evolutionary newcomers—basically, the rest of us. Other species benefit from the eons-long microbial activities that tap into otherwise unusable sources of energy or buffer extremely inhospitable conditions, in short, prepare new ground for all kinds of life.
Slime is a microbe’s protective armor, anchor, and cement, invisibly holding whole landscapes together. The Earth would look very different without it even though the goo has only been inadequately researched in many cases. But this is changing, both in the deep and on the surface of the planet. The role of biological adhesives is becoming a major focus of research, and not only because they’re under threat. Many of the ecosystems which slime has had a role in shaping could be fundamentally changed by environmental destruction, the loss of biodiversity and a warming climate. That is a threat to all of life, and humans too. Once-fertile areas could become dry and deserts expanded, coastlines could rapidly erode and global cycles could be destabilized.
Medea and the New Era
We live in a rapidly changing environment which will affect every living being, including us humans. What will the future hold—and what role will slimes play in it? They could help save us from our own environmental follies, or stifle whole ecosystems. They could give us inspirations for novel eco-friendly applications, or be lost before we even know about them. From technology to biomedicine, they offer a flexible Lego system of seemingly base hydrogels with an endless supply of extra pieces to customize them for every need and preference. Our own mucus protects us, but it can contribute to an unhealthy imbalance in our bodies. In short, slimes can offer new ways to connect us with ourselves, other life and the environment—or make already bad situations catastrophically worse.
The above quotes are from the nonfiction book Slime: A Natural History, Susanne Wedlich’s meditation on all things gooey. It is published by Granta Books and translated from German by Ayça Türkoğlu. It was first published in German as Das Buch vom Schleim in 2019, the Naturkunden series, and edited by Judith Schalansky at Matthes & Seitz Berlin.
Susanne Wedlich studied biology and political science in Munich and has worked as a writer in Boston and Singapore. She is currently a freelance science journalist for Der Spiegel, National Geographic, and Spektrum der Wissenschaft. She lives in Munich.
Cite This Source
Wedlich, Susanne. Slime: A Natural History, Granta Books, 2021.
