Wonders Large and Small

WONDERS LARGE AND SMALL

Our planet’s microbes (microscopic life-forms) remain mostly unknown to us. This is a strange state of affairs given their abundance and importance. It’s like there is an entire parallel universe of life right here with us and yet we understand relatively little about it. Despite our limited knowledge, however, we have managed to figure out that they pretty much run the planet. Microbes support processes on which human life and civilization depend. Our own bodies can’t even function without them. Not only are they around us, on us, and in us, but also microbes live in the muck at the bottom of the deepest ocean, miles below the surface of land in near-solid rock, and even up in the clouds above us. If you are attracted to mystery and monsters, then give microbes a chance because they’ve got it all. I can hardly look down at a patch of common dirt without hearing the voice of Edward O. Wilson, a scientist who specializes in ants but has a fondness for life even smaller. He admits that if he could take another lap in life, he would make a career in microbes:

Ten billion bacteria live in a gram of ordinary soil, a mere pinch between the thumb and forefinger. They represent thousands of species, almost none of them known to science. Into that world I would go with the aid of modern microscopy and molecular analysis. I would cut my way through clonal forests sprawled across grains of sand, travel in an imagined submarine through drops of water proportionately the size of lakes, and track predators and prey in order to discover new life ways and alien food webs. All this, I need venture no farther than ten paces outside my laboratory.6

Those who choose paranormal promises over scientific realities have no idea what they are missing. For example, I recently learned that Desulforudis audaxviator, a microscopic bacterium, has been found living more than half a mile down in the ground near Death Valley, California. This is believed to be the same species that was found a few years earlier living more than two miles below the Earth’s surface in South Africa. The account describes these tough guys living in a very hot (temperatures up to 140°F/60°C), sunless environment without oxygen. The striking claim is that a community could be sustained without other species supplying its energy. That is what alone means here—not a lone bacterium living for hundreds of millions of years. So how does it survive? What does it eat? It relies on the by-products of radioactive decay in the rocks around it. But the coolest thing of all about Desulforudis audaxviator is this: Scientists think some members of this species take wild rides up to the surface via natural water springs where wind blows some of them thousands of feet up in the air. After traveling halfway around the world, they ride raindrops back to Earth and then work their way back down to where they like it best, dark and deep.7 I don’t know how you feel about it, but I love sharing a planet with freaks like Desulforudis audaxviator. By the way, lonely as it may be for them miles down in rock, they certainly are not alone during their journeys up in the sky. It turns out that the air above us may be yet another huge and important ecosystem, one totally overlooked until very recently. The research cited here reports more than 2,100 different microbial types in air samples and describes microbes traveling from Asia to North America in the upper troposphere. It’s like they have their own highways up there. Some researchers think that these microbes are not just dormant hitchhikers but are active while in flight, possibly mating, for example. (Twelve-mile-high club?) It’s even possible that this microbial high-altitude highway has significant influence on the world’s weather.8

In addition to land and sky, the microbes seem to rule the oceans as well. The next time you are walking the sands of your favorite beach, glance out to sea and think about what is out there. Alongside fish, plankton, and dolphins, imagine the viruses infecting organisms throughout the ocean, from bacteria to whales. Their size makes them easy to overlook; their effects are harder to ignore.

It is now clear that the ocean is pretty much one big viral infection. Marine viruses are the most abundant form of “life” on all the Earth. (Viruses are so weird that technically they don’t qualify as life. But they’re close enough.) The estimate given here is more than one hundred billion viruses in a liter (0.26 gallons) of ocean water! That’s about the same number of all people who have ever lived throughout the entire existence of humans. The account also reports a million or more viral types in a kilogram of seafloor mud or sediment; what counts as a distinct type matters when interpreting such estimates. Most viruses are much smaller than even bacteria, so they weigh very little, of course. But they are so prolific that their collective weight adds up quickly. One comparison cited here puts their combined weight at that of 75 million blue whales. These are illustrations of estimated scale, rather than direct counts. An even more extravagant comparison imagines them end to end, stretching farther than the next sixty galaxies9 — Figure unavailable in the source files.

Okay, gaudy numbers and dramatic analogies aside, what’s the big deal about a bunch of creepy little parasites that float around, infecting fish, plankton, and everything else in the ocean? They matter because infections affect microbial populations and the movement of nutrients through ocean food webs. Those processes connect the living ocean to the atmosphere and life on land. It’s a common human fault to imagine that we are somehow above or disconnected from the rest of nature. The reality, however, is that we are far more dependent upon worms, bacteria, and viruses than we are on cars, computers, and credit cards. Given the importance of viruses to the way the world is, shouldn’t people devote some time to understanding a bit about them? But no, for millions of people, ghost hunting, astrological research, and other such pursuits beckon, and there is only so much time in a day.

Most viruses pose no direct threat to us, by the way. But that doesn’t mean they aren’t ruining somebody’s day. They have their chosen targets, and that’s just what viruses do. They can’t reproduce without hijacking a cell and turning it into their own personal virus factory, so their mission always is to invade and conquer. The account gives daily mortality estimates of about half of marine bacteria and 20 percent of ocean life. The latter figure is too broad to interpret without knowing which organisms and measure of abundance it refers to; it should not be read as an established daily loss of that share of every form of ocean life. This is amazing, especially when you consider what would happen if all those trillions and trillions of bacteria and other creatures were not being snuffed out by viruses on a daily basis. The food chain we rely on would be very different without viral population control—possibly not so well suited to our needs. For example, scientists have known for many years that the microbial ocean plays a major role in the Earth’s atmospheric makeup—and marine viruses have perhaps the biggest say in all of that. So, if you appreciate having food to eat and air to breathe, be sure to thank a virus.

If the virosphere still feels distant, consider the traces of viral ancestry in your genetic code. Like it or not, viral footprints are all over humanity. This might not go over well with people who still can’t bring themselves to invite bright bonobos to the family picnic, but viruses deserve a place at the table too. They have been around for billions of years, and that means they have coexisted closely with plants and animals, including us, so close that we are now part them. Our long and intimate evolutionary dance with viruses can’t be denied. It happened. It’s happening. But don’t worry; this is nothing to be ashamed of. We can take pride in having such prominent and influential kin.

As is probably clear by now, I’m so fascinated and excited by this branch of science that it’s difficult for me to shut up about it. As a result of living in the same house with me, for example, my otherwise-normal twelve-year-old daughter knows far more about viruses, bacteria, and mites than most college students. What I don’t understand is why everyone isn’t excited about this stuff. Science continues to pull back the curtain on a breathtaking and important show that’s underway. The more we learn, the more it becomes apparent that this is the microbes’ world and we’re just living in it. For example, “you” are described here using figures of 10 trillion or so human cells and about 100 trillion other cells and microscopic inhabitants, plus an estimate of one billion bacteria per square centimeter of skin. Such figures depend on what is counted, where, and how; they are not fixed counts for every body or patch of skin. The comparison between “you” and “other” life is a metaphor about sharing the body, rather than a biological definition of identity.

Right now, there may be herds of tiny Demodex mites grazing on your face like buffalo on the plains of nineteenth-century North America. Closely related to spiders, these microscopic beasts look like a medieval mace, the stick weapon with spikes on one end. Regardless of how clean you are or what you may be up to, these creatures are busy with their own lives. They mate on your face and lay eggs in follicles. The account describes them feeding on oily skin secretions.10 See? Reality is never boring.

Here’s a trick question you can irritate your friends with: How many visitors from Earth have been to the Moon? The likely answers you will get are: (1) Thirty or so because the astronauts took some frogs, worms, and bugs for experiments in space [Wrong, Apollo astronauts conducted no animal experiments on the Moon.]; (2) None, because the Moon landings were a hoax [Maybe you should find some new friends.]; (3) Twelve, the number of Apollo astronauts who landed on the Moon [Respectable answer, but also very wrong.]. The right answer, of course, is many, many trillions. Only twelve astronauts may have walked on the Moon, but every one of them was host to a staggering assortment of microbes at the time, so each landing was really more like a mass invasion.

Yes, you are a bipedal ecosystem, a kind of rainforest or coral reef with legs. Wherever you go, remember that you carry with you a vast and diverse collection of wildlife. You are a wilderness of known and unknown bacteria, viruses, and arthropods. And I won’t even bother going into detail about the fungal forests that cover large tracts of your body’s surface. Clearly you needn’t ever feel alone—because you’re not. I encourage you to think about these things when someone suggests to you that all the exciting and cool action is happening over on the supernatural/paranormal side of the tracks. No, reality holds its own just fine.