Invisible Empire , livre ebook

PRAISE FOR THE BOOK
‘Viruses have shaped human civilisation and life on Earth in ways we are only beginning to understand. Pranay Lal’s Invisible Empire shows us tantalising glimpses of powerful hidden forces that affect each and every one of us. Fascinating and illuminating.’
—SIDDHARTHA MUKHERJEE, Pulitzer Prize-winning author of The Emperor of All Maladies
‘Most of us think of viruses as agents of disease but they are among the most diverse and abundant organisms in the natural world, right at the boundary between the living and non-living. In this engaging and beautifully illustrated account, Pranay Lal takes us on a grand tour of the world of viruses, revealing their history and the amazing and varied roles they play in nature. Anyone interested in the natural world including young readers will greatly enjoy this book.’
—VENKI RAMAKRISHNAN, winner of the 2009 Nobel Prize in Chemistry
‘Viruses are one of life’s most powerful and mysterious forces, and shape our world in ways that we don’t fully understand. Invisible Empire illuminates a world which has so far only been looked at through the narrow lens of disease. This is one of those rare books that can truly change the way you see the world around you.’
—LARRY BRILLIANT, epidemiologist and author
Pranay Lal

Invisible Empire
The Natural History Of Viruses
CONTENTS
1 BOUNTY
2 A WHOLE NEW WORLD
3 SUPERSIZE ME
4 THE VIRUS IS US
5 A DEEP CONTROL
6 INVADERS, HITCH-HIKERS, SENTINELS, KILLERS
7 A SPOTTY HISTORY OF THE SPECKLED MONSTER
8 GUT FEELING
9 A VIRUS VANISHES
10 BEAUTY
11 HOW A VIRUS SAVED A GIANT
12 ZOMBIES
13 ENEMY’S ENEMY
14 QUO VADIS?
Notes
List of Illustrations
Acknowledgements
Follow Penguin
Copyright
1
BOUNTY
Let’s get this out of the way first:What, exactly , is a ‘microbe’? Quite simply: any life form that can only be seen under a powerful lens or microscope. And how many microbes exist in the world? If you were to say a trillion to the power of trillion, chances are you will still be well short of the actual number, which is likely to be inestimable, perhaps even unimaginable. Consider this: the ongoing COVID-19 pandemic (short for coronavirus disease 2019) started out as a tiny speck in the airway of a wild animal before it passed through hundreds of millions of human lungs, trailing havoc in its path. At the time of writing this, there have been nearly 122 million recorded cases of COVID-19 in the world. A British mathematician has, however, estimated that all of the world’s circulating SARS-CoV-2 (short for ‘severe acute respiratory syndrome coronavirus 2’, the causative agent of COVID-19) virus could easily fit inside the confines of a single can of cola!
From what we know, only an infinitesimally small fraction of microbes make us sick, even fewer have the power to kill us. Most simply pass through us, and a few use us as a suitable substrate to make more of their kind. They usually don’t bother us in the least and some, in fact, many , actually do us good.
In every pinch of undisturbed soil, in every drop of water, there live a billion bacteria and ten times that number of viruses. Every lungful of breath we take contains about a thousand microbes. Most of them are unknown to us. Into this mysterious universe of microbes, come the scientists diving deep, like Captain Nemo, stooped over modern microscopes. They sit gazing at a wondrous world to explore the lives of predators and prey, producers and parasites. Some of the microbes are solitary, a few are in conjugal bliss or are colonisers; many are barely minutes old, the rest are mature, dying or already dead. Each speck of life you see under a microscope has a well-defined role, and in their plurality, they make up habitats no less complex than that of a multi-storeyed tropical forest. The crucial difference is that life in the microbial world plays out several times faster. Microbes come in tantalising forms and often in geometry-defying shapes. They can be translucent and iridescent, twitching or fleeting as one watches them; a plethora of awesome diversity in just a thimbleful of pond water or in soil taken from under leaf litter.
There is no singular world of microbes. Every ecosystem has its own set of curious microbial communities—from the freezing ice of Antarctica to the hot sands of the Sahara, in the placid pond in your neighbourhood to deep-sea volcanic vents. They are everywhere. The surface of a pond teems with numerous photosynthetic organisms. Delve just a foot deeper and the character of organisms changes, while the benthic bottom of the pond and its sediments may have nothing in common with what is on top. A change of seasons or even the time of day can alter the proportions and number of microbes present. Microbial diversity shifts across the surface of the Earth as a consequence of the same three forces that Charles Darwin highlighted to explain the diversity of plants and animals— environment, dispersal and diversification. Microbes mirror the same geographic patterns of diversity as those found in larger organisms, with the variety of microbes (or bacterial species richness) twice as large in the warmer tropics than it is at the frigid Poles.
Microbes come in bewildering shapes, are deeply complex, and in terms of sheer numbers are unmatched by any other life form. Try this for size—it is estimated that there are 100 million times as many bacteria in the oceans (1.3 × 10 29 ) as there are stars in the known universe. There are more microbes in natural water than in the soil around it, or in the air above. Even on dry land, their numbers are immense and surpass the imagination. The average number of microbes in a single teaspoon of soil (10 9 ) is as large as the human population of Africa. The human jowl alone, on average, has more than 6 billion microbes that can be made up of more than 600 separate species. A single gram of the stale-smelling yellow grimy film on our teeth, good old plaque, has approximately 10 11 bacteria, which is about the same number as that of all the humans that have ever lived.

Under a microscope, a pinch of moist soil (1) from the edge of a pond reveals wondrouscreatures. A 2-millimetre worm-like nematode wriggles like a giant amidst the soil debris. About 4/5 of all animals on Earth are nematodes—there are 57 billion nematodes forevery human on earth. A single gram of soil can house up to several hundreds of these tinybacteria-feeding worms. If you dive deep using your lens, between grains of soil where thereare pockets of water you can see protozoa, like the translucent slipper-shaped Paramecium , gliding over one another (2). Shift along the slide and you will encounter a solitary cell ofa free-living freshwater alga with amazing geometric shapes like this Micrasterias (about 0.2 millimetres or 200 microns across [3]). Sharpen your resolution and move further along the plane of the slide and you may encounter a network of fungi with grey heads filled with spores (0.035 mm in diameter) which is Aspergillus (4).Alongside it is a bacterial colony of yeast (stained pink), and each of its individual cells are about the size of the knobby head of Aspergillus . If you are lucky, you may find a fungal meshwork called Arthrobotrys which uses its strands to lasso nematodes which it then slowly suffocates and digests. Each drop of pond water or soil is a complete ecosystem in itself, with its own producers, predators and prey, and parasites, and holds within it the excitement of a tropical safari!
Communities of microbes are so deeply interdependent that every species relies on one or more of another kind for its survival. The microbial world is organised like a town fair—under the microscope, you will see in a drop of pond water or diluted tropical soil a network of thread-like fungi that run like the tracks of roller coasters and toy trains. Next to them you may see a huddle of amoebae, and close by, congregations of different bacteria each minding their own business, but all in some way cooperating to exploit a particular environment. Pale-green photosynthetic creatures of various shapes and sizes compete for light; some jostle and trade for minerals they seek; a few may fancy their chances to mate or are in the act of gobbling up another while others are in active pursuit; and some still want to be the first to scavenge on the dying and the dead. The effect of this interdependence is deeply significant as it sets the tone of relationships for all life on Earth.
The interdependence of microbes with all life that we see around us began in deep time, long before we were even a speck on nature’s timeline, as it were. The earliest ancestors of modern microbes kick-started life in a hot and extremely inhospitable world. These minutiae forged partnerships to create colonies and together they broke down and recombined compounds to create new minerals, and especially, free oxygen. For nearly 3 billion years (from 3.5 billion years until 580 million years ago) microbes evolved, and slowly but inexorably and fundamentally, created conditions for multicellular life to emerge. Over these billions of years, microbes developed new cellular processes and chemical pathways which enabled them to utilise minerals and energy, like sunlight and heat, from the earth and water. This is the essence of the balance of the flow of minerals and energy which, at a most basic level, is maintained by microbes. All energy that fuels life rises and ends with microbes. Cooperation and collaboration exist among those with shared interests, whether or not they are related. And there are frequent wars between those who compete for resources.
Among all microbes, viruses are possibly the most enigmatic and certainly the most feared. Although you need special high-powered microscopes to even see them, they far outnumber and outweigh all other microbes. So much so that if just the 10 31 viruses estimated to live in the oce