Undeniable (26 page)

Among the fascinating aspects of bacteriophages is how specific they are. Only certain phages attack only certain bacteria. As I mentioned early on, a reasonable explanation for this is that they all came into existence about the same time. The key would be, as the car dealer often mentions on a television ad, volume, volume, volume. By producing enormous quantities of bacteria and enormous quantities of phages, the chances that they will find each other gets high enough to sustain entire ecosystems. That's part of what is going on within your microbiome.

Let's peer back into history to see how we got here. Bacteria in the primordial seas were undoubtedly attacked all the time by phage viruses, etc. There would be billions and billions of each. The key is that, when copies of molecules are made, mistakes or imperfections result. When a virus has managed to infect thousands of cells, each of which is producing thousands of viruses, that virus's ribonucleic acid (RNA, a relative of DNA) is going to get replicated with some mutations. Expand that into the future where we have tens of thousands of humans getting the infection, each of us in turn producing millions of viruses. Sooner or later a mutation is going to emerge that can infect, or reinfect, most of us.

Do we have to accept, then, that we are going to continually be infected by strange new strains of viruses, bacteria, and parasites our entire lives, and there's nothing to be done about it? Well, in the same way we take steps to avoid getting injured by trees we're cutting down, or traffic we're crossing, we take steps to avoid getting infections. We wash our hands and avoid sick people, at least to the extent possible. I remember well being kept inside during certain summers to avoid being exposed to the virus that causes debilitating polio. So it is logical that we, as a scientifically literate society, take steps to create immune responses inside our bodies as well as outside. We can, because we understand evolution.

With all the mutations going on, crafting a flu vaccine is like shooting a needle at a moving target. Every winter, when flu season begins, the viruses that are circulating are slightly different than those from the previous season. That is why the CDC works with the Food and Drug Administration (FDA) and the World Health Organization (WHO) to anticipate the next season's troublesome strain of flu virus. The general trick is to capture or get samples of the flu viruses infecting people in the Southern Hemisphere during their winter and prepare vaccines. It is an evolution-driven health system that almost everyone takes for granted.

Pathologists—scientists who work with and study infections like the flu—prepare a vaccine either by using a virus that has been weakened (attenuated) a little bit with a chemical reagent, or by using a dead or completely disabled virus that is still structurally intact. It still has the right configuration of proteins for your body to recognize, so it triggers an immune response, but it is not capable of causing an infection on its own.

The first order of business for the immune systems is to recognize incoming viruses, bacteria, or parasites that are unwelcome inside us, because those pathogens have schemes for taking control or hijacking our cells to do the work of making more viruses or bacteria. (Along the way, the immune system needs to ignore benign microbes, as well as the body's own cells.) Once your body recognizes an unwanted intruder—an infectious agent—it can send antibody proteins to wrap up the virus and pry it apart. To do this antibodies have to be attuned to a pattern of proteins on the outside of the invader. If your immune system, with its antibody molecules, does not recognize an infectious pathogen, your immune system does not respond, at least not right away. That gives the virus, bacterium, or multicellular parasite a tremendous head start, and can make you very sick.

The reason these infectious organisms are still here is that they're always changing, always mutating as they reproduce, taking on new chemical identities that the immune system does not recognize. They are always evolving in a way absolutely consistent with what we predict per evolutionary theory. Germs and parasites evolve with remarkable speed in geologic terms or in comparison with the amount of time life has been on Earth. That's their business. We humans, as their slowly evolving victims, have to make it our business.

Bacteria take chemicals out of the environment to run their metabolism. After consuming the right amount of the right chemicals, bacteria have enough chemical energy to reproduce. They do that by splitting themselves in half. Of course, it's a bit complicated biochemically speaking, but the idea is just that. We call it binary fission—splitting in two. That would be fine for the bacteria, but as they reproduce and metabolize the chemical environment around them, certain of them produce miserable toxins that make us sick.

In some primordial age, a bacterium chanced upon a way to produce toxins that made one of our ancestors sick. That was a great day for bacteria-kind, because they had come across an effective way to spread themselves around. Our ancestor may have had so much toxin in her nose that she sneezed on others in her tribe, spewing live bacteria with her saliva and mucus. Or she may have been just breathing air laced with bacteria-bearing water drops in the stream. Or,
ugh
, bacterial toxins may have produced diarrhea. And as our ancestor's body was, uh, ridding itself of toxin, it was also spreading the bacteria. Once a bacterium or family of bacteria came across this scheme, it's hard to stop. But human scientists came across a few very effective techniques.

Bacteria have a cell wall that keeps the microbe separate from its environment. Within the wall is a membrane that keeps different organized subsystems or “organelles” within the bacteria separate. Humans have found a way to make the proteins, the molecular structures that hold the bacterial cell wall together, fall apart or pry open. When that happens, a bacterium spills its guts; it falls apart and stops metabolizing and producing toxins.

The molecules that pathologists craft and chemical engineers work to mass-produce in oil-drum-sized “reactors” are what we generally call antibiotics. Perhaps the most famous among them is penicillin. You may have heard the story of Alexander Fleming, the Scottish biologist who noticed in the 1920s that the
Penicillium notatum
mold can kill the
Staphylococcus aurius
bacterium that causes staph infections. You've definitely heard of the bacteria-slaying compound he isolated from those molds: penicillin. Fleming realized that if this mold could be isolated and produced in large quantities, it would be very effective against bacterial infections. Penicillin ended a great deal of misery, and it saved countless lives.

Along with those measurable benefits, penicillin led to the development of dozens of other fantastic antibiotic drugs: ciprofloxicin, polymixin, tigecyclin, and a great many more. Some of these drugs keep bacteria from dividing or reproducing; others kill the bacteria outright. Either way, antibiotics have changed the world and completely changed the expectations of modern medicine. Our most dangerous enemies, germs and parasites, were all at once easy to kill and overcome.

But the process of evolution has rendered a great many of these drugs far less effective than they once were, even useless. Since bacteria are able to reproduce so quickly compared to the organisms they attack and exploit, they also mutate quickly. Over just a few years, genes that conferred resistance to the drugs were randomly created or acquired. The result: A tremendous number of bacteria that were once quite controllable are now troublesome at best, deadly at worst. Evolution is enabling them to bite back, and that's bad for us.

Medical professionals nowadays have come to realize the gravity of the problem, and have been warning the public that overuse of antibiotics is making them ineffective. The more of these drugs we use, the more chances infectious bacteria have to come in contact with them, and the more likely these bacteria are to come up with descendant strains that are able to chemically protect themselves from the effects of the drugs.

I have participated in campaigns encouraging people, especially anxious parents, to not overuse these wonderful products of science. You may be among those who have, or who know someone who has, had a sick kid. The parent takes the kid to the doc and is so aggressive or concerned or sympathetic that the doctor prescribes antibiotics for a disease that the patient's immune system would have beaten eventually anyway.

Furthermore, because of their completely different chemical mechanisms, viruses are unaffected by the drugs that target bacteria. It has to be a bacterium that's infecting you for an antibiotic to do any good. (Don't ask your doctor for an antibiotic if you have the flu; it won't do a thing except help breed more dangerous bacteria.) Viruses have no cell walls to breach. They have to be attacked with antibodies that are tuned to find them, and find them fast. That's why the medical community has sponsored campaigns encouraging consumers and health care providers to “Take the Right Drug for the Right Bug.”

It's also important to finish your antibiotic prescription. That is to say, if your doctor gives you a two-week course of antibiotics, be sure to follow it all the way through, even if you start to feel fine in just a few days. Otherwise, you will probably not have killed all the bacteria that are in you, and the ones that are still hanging around will probably have a tendency to be immune to the antibiotic. They may not have complete immunity, but a fractional resistance will be passed on to subsequent generations of your germs, and they will be resistant to the same drug after you've passed your infection along to some other hapless victim and soon-to-be patient. You'll be aiding and abetting the enemy.

This all happens by the exact same evolutionary process that brought about all the creatures and ecosystems that are extant in the world today. It is modification by natural selection, it just happens to be taking place in bacteria. It is one more vital reason to promote universal science literacy: Evolution is a matter of life and death.

 

27

THE IRRESISTIBLE URGE OF ALTRUISM

I'll admit that the last couple of chapters have been pretty downbeat, and make evolution sound as if it's out to get us. Near as anyone can tell, evolution is not guided by a mind or a plan. It just
is
. Our perceptions of whether evolution is being generous or malevolent are based entirely on whether we think that we are the ones coming out on top—which, come to think of it, is a very evolutionary way to look at the world. So take what I'm saying as an entirely subjective message, but I think of this as a much happier chapter. It is about a topic that benefits all of us: altruism, the instinct that makes us look out for one another.

Let's start with an example from my childhood. Like my father, I was a pretty good Boy Scout. I was, and am, pretty good in the woods. I can split wood, start a fire, rustle up some grub, lash spars, set up shelter, and find my way out of the woods through unfamiliar territory. Along with the exploration activities, though, part of the deal with the Boy Scouts is to help out in the community. You're required to do a good turn daily, to help someone every day, even if only for a few seconds. One of my modern mottoes is posted on
billnye.com
: “To leave the world better than you found it, sometimes you have to pick up other people's trash.” I guess my altruistic impulses came from my mom and dad. They did their best to leave the world better than they found it (you may have to forgive them both for begetting me, I suppose. My mom always said dad was a great dancer; I guess one thing led to another).

When I first entered the workforce, I volunteered at the Pacific Science Center in Seattle. I helped move boxes around on weekends, and I served as a “science explainer” now and then. It just makes a feller feel good to help out. The demonstrations skills I learned there led me to a whole career and the writing of this book. I was also a tutor through the “I Have a Dream” program. Both of these early jobs are examples of altruism, expending energy for the good of another. I like to think I was good at my work, but I always felt I got more out of it than the guests at the Science Center, or the students on Saturday mornings. I've had that experience many other times—when teaching a class or performing a particularly good science demonstration. I claim that I can sense it inside myself and inside others—that this type of altruism is encoded within us somewhere.

Religions often preach about the importance of doing things for others. There are countless not-for-profit organizations that promote the idea of service for the betterment of our neighbors, or for those less fortunate than we are. If you volunteer or serve others, I presume it makes you feel pretty good. Most of us take satisfaction in helping others. Most of us feel good when we believe that we've done the right thing. Just like you and me, evolutionary biologists call the phenomenon of doing the right thing “altruism,” although they define it more rigorously. The word derives from the Latin words for “to this other.” The origin and nature of altruism is one of the hottest areas of research in evolutionary science today.

In conversational language, altruism refers to being selfless, to helping another without expecting any reward. In evolutionary biology that idea is expressed in an equation: An individual provides or gives a service while gaining little or no benefit to her or himself. Specifically, the cost is greater than the reward or benefit. That relationship can be written very simply as

b < c
(benefit for the giver is LESS THAN cost to the giver)

There is always some cost in offering help, whether it is measured in time, energy, or risk of getting attacked. Meanwhile the recipient receives benefit—something like food, sharing the carrying of a heavy load, or a warning of an imminent attack by a predator—while the giver does not, at least not in an immediately obvious way. Scientists interested in the origin of this tendency in many animals, including us, have studied altruism in all kinds of intriguing ways. Much of that research circles around the basic question of altruism: In the battle for survival, why would any individual favor costs over benefits?