HENRY PERRY raises his wine glass to his nose and inhales the rich scent of the claret. Across the rim of the glass he stares into the startling blue eyes of the young woman he bought for tonight. She is dressed in lavender, and her auburn hair falls onto bare shoulders. Henry hasn’t seen such pale and perfect flesh in months. Her name is Adrienne, and she smells of musk. She smiles at Henry as his eyes swallow her.

He is enjoying himself. For the past six months he has fought trench foot and Germans in the mud at Soissions. But not tonight. Tonight, Henry’s uniform is only for show. His eyes and his nose and his mouth, even his bravery, are for Adrienne only. Henry places his wineglass next to his linen napkin.

“You are a lovely woman, Adrienne.”

“And you are a lovely man,” she says to Henry in words wrapped in the syrup of her French.

Henry laughs nervously.

But she is right. Henry is young, blond-haired, and tall. The weeks at war have thinned him, and now he is shaped more like a man than a boy. His uniform, by some monumental accident, fits him perfectly. Tonight, Henry’s long arms and legs seem just right to Adrienne and the others who have noticed the young American and his escort.

The waiter, in his clipped French, interrupts to ask Henry if he would like more wine. Adrienne translates.

“Tell him I do,” Henry says to her. “Tell him I want all the wine he can bring. And then I want you.”

Adrienne tells the waiter to bring one more bottle of wine. Beneath the table she adjusts her stockings and straightens her skirt. She reaches across the table for Henry’s hand. Oddly, she finds a nugget of eagerness inside her own stomach this evening. How surprising, she thinks. The waiter arrives with another bottle of wine and uncorks it as they both watch. He fills their glasses and leaves. The lights here are dim, the carpet and curtains thick, the food spiced. Before the war, lovers came here often to sit in dim corners beneath dark wood and eat from one another’s forks.

And that’s what those who surround Henry and Adrienne imagine them to be, lovers. But these others, with their own reasons and purposes tonight, are wrong. Henry and Adrienne are not lovers. Theirs is a practical arrangement. Henry and Adrienne have agreed on the cost of love, and it is too high. Both are here for something else, something less expensive, something a soldier on a short furlough can afford. Or so they think.

Everything Henry sees is just as it should be this night. The room, the candlelight, Adrienne, her dress, her ears, her mouth, her neck. The thick red wine and the salty food. Outside, even the darkness seems dressed just for Henry and Adrienne. The things he cannot see, Henry has decided to ignore. There is so much to leave behind—the Germans, the trenches, pieces of people in the mud. Not tonight.

Tonight, Henry will fill his eyes and thoughts only with Adrienne. Who could blame him? But in the end, that choice will cost Henry his life.

“Is it time?” he asks.

“Nearly,” she says.

Neither of them expects any of this to last beyond tonight. That is what they have planned. That is what they have agreed upon. But there are others here tonight, making plans of their own.

By the time I met Henry, he could no longer speak in complete sentences.

He couldn’t walk the fifty feet or so across our backyard without jerks and staggers. Sometimes he drooled. These were Adrienne’s gifts.

Henry was living, then, at the VA hospital in Salt Lake City, Utah. Every Sunday afternoon, my father would gather him up in our family’s Ford station wagon and bring him out to our house in Bountiful for dinner. Henry seemed to like that.

Henry was my mother’s brother. She and her mother, who lived with us then, had arranged for Henry to be moved from the VA hospital in Kansas City to the VA in Salt Lake City so that he would be closer to them.

His eyes were still piercingly blue, his hair still blond, though mottled with gray, and he still had the whippet-thin frame of a soldier. But the rest was no longer Henry.

In spite of his peculiarities, or maybe because of them, I enjoyed my uncle. He cursed and spat and wore soiled clothes, all of which I admired. But even I could see that something about Henry was not right.

More than once I asked my mother to explain Henry’s peculiarities, but it wasn’t until long after his death that she told me the truth. Henry had syphilis. For my mother, that was a like slap in the face. Syphilis was a disease of the poor, the deviant, the unwashed. It was a sickness that fell upon the godless as punishment for their sins.

Syphilis, of course, isn’t punishment for anything. It is a disease caused by a bacterium––Treponema palidum––a little curlicue of catastrophe known as a spirochete. T. palidum moves from person to person during the most intimate of human acts. Wounds, torn tissues, cracked skin are all open doors for syphilis.

That night in Paris, another was sitting at the table with Henry and Adrienne, one no human could see, but one who knew full well that this was not to be a one-night stand. Even Adrienne’s eagerness that night was fired by the bacterium. The next morning, as Adrienne stayed behind in her small flat overlooking the Rue Michelet, the spirochete left with Henry.

Fleming’s penicillin wouldn’t come along for decades, so over the years, T. palidum had its way with Henry. First, there was a minor wound, a chancre, not at all painful. And then it went away. Henry was relieved. Later, a rash spread across Henry’s palms and the soles of his feet. He assumed it was left over from the trenches of France.

Headaches followed. Then the spirochete took Henry’s joints—his knuckles, his knees—then it took his eyes, his spine, and his mind. When there was nothing more to take, T. palidum took my Uncle Henry’s life. After all, Henry had dared to take a night off from the war and a moment’s pleasure from a beautiful woman in a simple flat one night in Paris.

A microscopic curl of protoplasm, overlooked in the frenzy of lust. When I finally understood what happened to Henry, I was shocked. Not because Henry had acquired his disease during an act of illicit love, but because of the immensity and the voracity of his infection. The idea that something as tiny and as simple as a bacterium could so unrelentingly and so easily take both a man’s mind and his life scared me.

That, of course, changed nothing. A single child’s fear was of no consequence to the dominant form of life on planet Earth.

That’s simply how things are.

Henry was my uncle. But Henry’s story is not unique, not nearly. Bacteria are the most numerous living things on Earth. Everything on the face of this planet, living or dead, has been changed by bacteria––the color of our skies and seas, the air we breathe, the soil beneath our feet, our immune systems, our digestive systems, and each and every human cell. Infection is the way of life. We owe everything we have to bacteria.



The Bacteria That Make Us Human

I read a science fiction story once in which space travel for humans was possible only when men and women were disassembled into their component cells and stored in vats of salt water. In this way, while rockets accelerated to the enormous speeds needed to reach distant planets during anyone’s lifetime, the effects of the massive g-forces were diminished.

At the end of such trips, a very complicated computer would suck up each man and each woman from their tubs of brine and reassemble them into human beings.

One young woman, faced with the prospect of dis- and reassembly, expressed considerable concern over the computer’s ability to put her back together properly. And worse, she wondered if the computer erred whether she would ever know.

To assure herself of accurate reconstruction, she asked a male friend to go over her body very carefully before and after the space flight. Not surprisingly, he agreed. And in the end, he concluded that the woman was herself once again. This reassured her. But the man’s assertions were meaningless. There was no way he could possibly have known if she was or wasn’t the same woman.

Each of us is made from billions of little bits of life. In an average person, there are about 1.1 × 1014 of these bits. That’s 1.1 with thirteen zeros after it. 1.1 × 1014 is roughly equal to the number of seconds in thirty million years, one hundred thousand times the number of people on Earth, the number of thimblefuls of water in the ocean, or the number of grains in a hundred thousand cubic kilometers of beach sand. A lot of bits. We call these bits of living things cells—skin cells, red blood cells, white blood cells, liver cells, nerve cells, epithelial cells. Certainly 1.1 × 1014 is more pieces than any man could verify in a lifetime, regardless of how earnestly he might try.

But let’s suppose the young man could have checked every single cell in the young woman’s body (after all, this was science fiction). When he did, he would have found something startling. After their long space flight and biological metamorphoses, he would have found that the woman’s body contained nearly ten times as many bacteria cells as human cells. And if, as he panicked over this discovery, he had checked his own body, he would have found that most of his cells were also bacteria.

Imagine their horror. Imagine the setback this would have dealt space travel if word of it had leaked out. But the bacteria inside both of them had nothing to do with their space flight. Though we don’t often notice it, every human is mostly bacteria. In an average human body—even one that has never left Earth—only about 10 percent of the cells are what we call “human” cells. The rest—the vast majority, about 90 percent—are bacteria.

And, actually, not even one of the 10 percent of cells we call human is fully human. Even these cells contain bacteria. That means, as I write these words, by cell number I am less than 10 percent human—and that’s stretching it. And as you read these words the same is true of you.

Humans are at best only 10 percent human.

How does this happen? How does each one of us come to be so massively infested with these microscopic vermin?



Betrayed at Birth

At the dark moment of fertilization—when, with a final flash of its pearly tail, a sperm penetrates an egg—we are more human than we will ever be again. Sperm, egg, zygote, blastula, embryo, human. And for the next nine months, nestled in the sterile seas of our mothers’ wombs, we remain nearly human.

But as birth nears, everything changes. In anticipation of our arrival, soon-to-be mothers begin preparing a special nursery. Inside these women’s birth canals, bacteria sprout like weeds. Lactobaccili, the same bacteria found in yogurt and buttermilk, divide and spread throughout the passage that we must traverse as we enter this world. Like tiny sausages, about one-one hundredth the thickness of a human hair and as long as one-twenty fifth the thickness of this page, these bacteria rise like fingers to prod us into reality.

Then, on our way into this world these bacteria immediately infect us. Before our mothers have shared so much as a single caress, they have inoculated every one of us, infected us with billions upon billions of squirming, wriggling, living bacteria. Before we draw a first breath, our own mothers have compromised our humanity.

And cruel as that seems, it appears they must. If Lactobacilli don’t flourish inside a mother’s vagina, premature delivery happens more often than in infected mothers. And infants born prematurely or by cesarean section face many challenges that full-term and fully infected infants don’t. So everything conspires to ensure our immediate infection.

After birth, things get dramatically dirtier. Our first breaths, the arms of the doctor, or midwife, or forest floor, the mother’s breasts—all are teeming with microbes. Even in the relative sterility of a hospital delivery room, we roll in the powdered sugar of this world like a warm doughnut fresh from the oil. And as we do, we are quickly covered with layer upon layer of bacteria and fungi and viruses and even a few parasites. Life as a separate entity is over. From this moment on, no one of us ever walks alone.

As a mother nurses her child, she lays the groundwork for further infection. The milk she feeds her child is laced with proteins. Some of these proteins are fertilizers for more infectious microbes, especially Bifidobacteria.

These bacteria push aside a few of the Lactobacilli and attach to the baby’s intestines. Together these two bacteria weave a blanket inside the child, a protective blanket.

Children with too few bacteria often develop a disease called oral thrush. Candida albicans causes oral thrush. Candida albicans is a yeast, the same yeast that causes vaginal yeast infections in women. Without protective bacteria, a child’s mouth sprouts thick white crusts of yeast across cheeks and gums and lips. As it spreads, Candida albicans digests the human tissues beneath and causes painful destructive ulcers. Without bacteria, life is harder.

The process of our infection appears completely chaotic, but it isn’t.

Lactobacilli and Bifidobacteria come first. Then, as the mother withdraws her milk, the Bifidobacteria give way to other strains of bacteria, and much later, as the hormones of puberty flood the body, still other bacteria arrive and thrive. Layer upon layer is laid down. Ordered and structured by time and chemistry, we absorb our surroundings. Literally, we become what we eat, or drink, or touch, or breathe. We are what we wear. We become those who caress us and whom we caress in return. From the world that surrounds us, we gather ourselves.

Once a pulp of nearly pure, pale, human cells, we transform into a microbiological metropolis covered with living things whose names read like a Linnaean litany—Staphylococcus aureus and epidermidis; Streptococcus mitis, mutans, viridans, pyogenes, and pneunominiae; Trichomonas tenax; Candida albicans; Haemophilus influenzae.

Our skin sprouts a cornucopia of microorganisms, including at least four different strains of bacteria and several species of fungi. Our eyes gloss over with three or four strains of bacteria. Noses, throats, the upper reaches of our respiratory systems clog with more than six different types of bacteria. Mouths bloom with half a dozen species of bacteria and fungi. Lower urethras fill with more than ten different bacteria, a few fungi, and a parasite or two. But, by far, the greatest numbers of bacteria settle and prosper in our intestines. In places, the bacterial coat in our large intestine is an inch thick. And our feces, by dry weight, are 50 to 60 percent pure bacteria.

While no one notices, and with little or no effort on our part, we become a menagerie, a walking ecosystem, a universe apart. This world is infectious. So whether we like it or not, wherever we go, hosts of others follow.

There is no longer an “I.” Now and forever, there is only “we.” And it isn’t just the number of microbes that is staggering. The bacterial genome (bacterial DNA) within each of us contains roughly two million distinct bacterial genes.

When scientists sequenced the human genome, they found only about thirty thousand to fifty thousand different human genes strung out along human chromosomes. But the chromosomes our parents gave us do not hold all of the genes inside of us. The bacterial genes we gather far outnumber the genes given to us by our mothers’ eggs and our fathers’ sperm. Amazingly, nearly 99 percent of the genes inside of human beings aren’t human.

Because human cells, like those in our blood and skin and livers and hearts, are about one hundred to one thousand times larger than bacterial cells—by mass and volume—people appear mostly human. But they aren’t. And to exclude the bacterial genes from the human genome is not only arbitrary, it’s inhuman.

Infection and Individuality

Through processes that begin with our first breaths, we rapidly change from isolated human beings into symbiotic systems with whole communities of living things sharing a single space. What we need we take from the world around us: parents, aunts, uncles, foods, toilets, toothbrushes, tables, automobiles, strollers, sidewalks, trees, dogs, cats, rats, spoons, spit.

Surprisingly, though, the community of bacteria within one man or one woman is not simply an accidental consequence of birth and geography.

Where we are born is unquestionably important. Infants born in developing countries acquire bacteria that differ considerably from those of infants born in developed parts of the world. Children born in different hospitals may have very different strains of bacteria in their intestines. And breast-fed babies’ intestines contain mostly Bifidobacteria, while formula-fed babies’ intestines have many more potentially dangerous bacteria, such as coliforms, enterococci, and Bacteroides. Where we are born and what we eat do make a difference. But our surroundings and our food are not the only factors.

Among humans, identical twins resemble one another most closely. Identical twins, also called monozygotic twins, arise from a single sperm and single egg. These children have the same chromosomes and the same human genes. Usually, identical twins also live in the same home, eat the same food, breathe the same air, and drink the same water. As you might guess, the communities of bacteria inside identical twins are themselves nearly identical.

Beyond monozygotic twins, things change quickly. Even within a single geographic area, the species of bacteria found inside people vary dramatically from person to person. This is true even between married people living in the same home, eating the same food, drinking the same water, and breathing the same air. You and your spouse, partner, brother, or sister house significantly different collections of bacteria.

She might have a little more Staphylococcus aureus (the cause of toxic shock syndrome) in her nose or vagina than you have. Candida albicans might find him a little more attractive than you. Helicobacter pylori (part of the cause of peptic ulcers) makes a living for itself in some stomachs and small intestines but not others. Citrobacter (which can cause diarrhea and perhaps meningitis) is comfortable with some of us but not others. Our collections of bacteria are unique, perhaps as unique as each one of us. Bacteria, the creepy, crawly, and slimy parts of this world, may be just as important for making human individuals as are brains or genes. Who I am depends on who they are, and vice versa.

The day we arrive in this world, they are waiting for us—our own unique ensemble of bacteria. And we have no choice but to welcome them. Which is as it should be, because without them we are not whole.



The Bacteria That Stick

Some of the bacteria that colonize us are itinerants, just passing through on their way to an intestine more to their liking. But the majority of the bacteria we attract are in us for the long haul. These bacteria we call normal flora. “Normal,” because these species of bacteria are found in “normal” (without obvious disease) people. And “flora,” because some bacteria more closely resemble plants than animals.

We acquire our normal floras with no effort whatsoever. We eat, we breathe, we poke our fingers into the soft parts of this world. In the process, we gather billions upon billions of bacteria—as easily as a ship’s hull gathers barnacles.

In the Coit Tower in San Francisco, Victor Arnautoff—inspired by Diego Rivera—painted a mural that depicts a life on the streets of the city. The painting is done in muted blues and rusts and tans and in Rivera’s Depression-era style. In the background, streets stretch off toward oblivion. In the foreground is the pastiche of daily life in the city.

A police officer is placing a call to headquarters; a man is reading a newspaper; two uniformed sailors are making their way toward the pier; another man is unloading crates of food next to piles of carrots and lettuce; women are holding hands with their children and moving toward the shops; other men and women move between tasks; a man collects the mail while another has his pocket picked as he checks the time; truckloads of grain arrive nearby; an elevated trolley carries people downtown as trainloads of cargo arrive in the rail yards; factories belch smoke, a fire truck races to a blaze, and women stand on the paved walks and share stories. Although it seems chaotic, it intertwines as artfully as a symphony or a colony of ants. Some provide food, others defense.

Some bring news, others clothing. Some carry food. Some are dying. Some worry over war. Some are sleeping. And each relies on the other, each depends on the rest. Move one, and the sense of what is happening changes.

Inside of every one of us, this scene is played out day after day after day. Intestines deliver foodstuffs, eyes bring the news, the immune system keeps track of the bad guys, the liver cleans the water, and the red blood cells purify the air. The mind worries. The blood flows.

Like City Life, each of those inside of us relies wholly on each of the others. But unlike Arnautoff’s mural, inside humans one group stands out from all the rest, outnumbers all the others taken together – bacteria, the ground stuff of life. Underneath and in between every brick, bacteria thrive. And that mortars it all together.

Our bacteria are not barnacles. They’re not just along for the ride.

Our bacteria are paying passengers.

My Uncle Henry lost his mind because of a fling in France, Treponema palidum—a bacterium—and syphilis. One night in 1914, the Denver and Rio Grande Western Railroad sliced open my grandfather’s foot and opened the gate for Clostridium perfringens—a bacterium. Before it was done with him, that bacterium took all of my grandfather’s foot and a sizable chunk of his leg.

Untold thousands of others have lost their lives because of a single breath they took, a fleabite, a drink of water, a wound, and Mycobacterium tuberculosis (TB), Yersinia pestis (bubonic plague), Vibrio cholerae (cholera), or Clostridium botulinum (botulism)—all bacteria.

We notice that. Bacteria reach out and slap us in the face then. It’s in the papers, the magazines. It’s on TV. It’s the reason we thought we went after Saddam Hussein. Agents of death and disease, that’s what bacteria are. And sometimes, that’s true. Some bacteria do make us sick and kill us. But that’s only part of the story, only the tiniest part.

Bacteria outnumber humans by a factor of 1020 (that’s 100,000,000,000,000,000,000). The oceans are full of them, the earth teems with them, we are covered by them. Everything on this planet teems with bacteria. If bacteria were simply malignant agents of disease, none of us would be here today.

It’s true that bacteria took my Uncle Henry’s eyes, then his legs, and finally his life. And that’s a terrible story. But bacteria also gave Henry life to begin with—a considerable gift. It was humans who sent my uncle off to war.