Monday, January 29, 2007


Hi Bill,

There are so many antibacterial items on the shelves these days, I'm not sure what to choose. Should I even use antibacterial anything?

--Sanitary Sarah

Dear Sarah,

No. Well, mostly no. Almost always no. Most of us should avoid antibacterial products. People in health care may be the only exception. For the rest of us, antibacterial soap started out as a pretty good idea, but it could be turning into a big mistake. Antibacterial soaps and ointments, for example, may be unintentionally creating germs that are resistant to antibiotics. Eventually, our antibiotics may not do much of anything to slow the spread of these types of germs and the diseases they cause.

The miracle of antibiotics
For many years, antibiotic drugs worked so quickly and so effectively that they seemed like magic. In magic, they say, it's all done with mirrors. Well, in biochemistry, it's all done with molecules. Antibacterial molecules inhibit or disrupt the action of enzymes in an unwanted germ's fatty outer layer or in the layer itself--the germ's cell wall. The wall is a polymer, and without the enzyme working properly, the wall molecules cannot "cross-link" (so the germ can't cause us harm). Instead, the walls fill with water and burst. Our own cells are unaffected by any of these antibiotic compounds. We don't have cell walls like these; we use different enzymes, probably because our cell membranes came to be somewhat later in history than bacteria. (Some people are allergic to antibiotics, but that's different chemistry and a different problem.)
Anatomy of a Simple Bacterium (Image credit: Microsoft Corporation)
Anatomy of a Simple Bacterium

Antibiotics are like a bit of chemical genius, but we didn't invent these molecules; we discovered them. Fungi and bacteria came up with them. Alexander Fleming is generally credited for realizing that Penicillium notatum fungus was inhibiting or controlling the growth of bacteria in his lab in 1928. He published his landmark paper in 1929. There must be an evolutionary advantage for fungal organisms that can produce chemicals to inhibit the growth of bacteria that might cause them trouble. And bacteria, like all the rest of us living things, are always fighting off other bacteria. They make their own antibiotic compounds often called bacteriocins.

After discovering the antibiotic properties of Penicillium fungi, for example, we found ways to brew up these compounds by the vat-full. This is a modern way of destroying germ cells.
Discovery of Penicillin (Image credit: St. Mary's Hospital Medical School/Science Source/Photo Researchers, Inc.)
Discovery of Penicillin

The old-fashioned way
Another somewhat older-fashioned way of chemically tearing germ cells apart involves alcohol. When applied topically--directly on the skin--alcohol kills nearly everything, germ-wise, by destroying the cell walls of typical germs.

Try this: Put a drop of water on wax paper. Dip the tip of a toothpick in rubbing alcohol. Touch the tip to the edge of the water drop. In a moment, the water drop will lose its shape. Its surface tension will be greatly weakened and it will fall apart. So it goes with germs on your skin. Their cell walls are destroyed by the strong pull of alcohol's chemistry. Alcohol hand sanitizers are very effective for this reason. Most of them are alcohol mixed with hand lotion. Not bad, antiseptic rather than antibiotic. But once a germ is inside you, infecting you, you can't possibly get the concentration of alcohol in your system high enough to kill germs without killing yourself.

Another old-fashioned alternative to antibiotics is good old soap. Soap works by washing germs and dirt and all kinds of other things away, and it's very effective. Soap has molecules that are like long chains (well, long by atomic standards, maybe a nanometer, 0.000001 millimeters, 0.00000004 inches). One end of the soap molecule is polar, like the poles of a magnet (or the planet Earth). The polar end associates with and dissolves in water. The other end is nonpolar. It associates well with grease and the oils on your skin. To achieve this remarkable effect, most soap recipes include sodium, which makes that water-loving (hydrophilic) end of the molecule essentially dissolve in the nearby water molecules. Consider how well sodium-chloride salt dissolves in water; the surface of our world is almost all sodium salt--ocean.
Alignment of Polar Molecules (Image credit: Microsoft Corporation)
Alignment of Polar Molecules

When soap is mixed with water, the soap molecules get between the water molecules, driving them apart. The slightly more distant water molecules don't pull on each other as strongly. This action is a bit like a bunch of atomic-scale refrigerator magnets. When a magnet is holding a recipe printed on a thin piece of notepaper, it has a tighter grip than a magnet pulling through a thick piece of a cereal box. The farther a magnet is from the surface, the weaker the pull--and the same is true with water and soap molecules.

Soap lowers the surface tension of water. So, the surfaces that the soapy water comes into contact with get especially wet. When the water molecules flow, the germs flow away with them. For most activities, that's all we need. The only exception might be when medical teams put their hands inside you. In that case, germs on their skin could get under your skin, if you get my drift.
Action of Soap on Dirt (Image credit: Microsoft Corporation)
Action of Soap on Dirt

Tougher germs
Antibiotics changed the world. People in the developed world just don't die of diseases the way they used to. For example, if you take a walk around an old cemetery, note all the people who died before they were 10 or 12 years old. Germs got most of 'em. Antibiotic compounds cured so many people so quickly that for many decades the term "miracle drug" seemed to be the least we could say about their wonderful properties.

We've produced antibiotic compounds for over 60 years. But, here's the thing: This antibacterial chemical enzyme-attack scheme is not perfect. Why is that? Some germs, by the random chances of genetic mutations, happen to have lipid membranes with enzymes that aren't inhibited, disrupted, or driven apart as readily by the antibacterial compounds. So, they survive. Then, like any successful living thing, they reproduce. Those offspring, the next-generation germs, get the resistance genes and are themselves resistant to the antibacterial agent.

We have been living and dying with germs for millions of years, but antibiotics were discovered less than a hundred years ago. These drugs and chemicals have been very effective in knocking germs apart or disrupting their various internal chemical activities. But because germs reproduce so fast, we will never wipe them out.

This process of germs mutating in such a way that our antibacterial chemicals don't affect them anymore is a classic example of evolution and natural selection. So you could say that our fancy soap is selecting the toughest, most resistant germs for reproduction.
Charles Darwin (Image credit: Culver Pictures)
Charles Darwin
Another way of looking at this is that germs are continually redesigning themselves, from the bottom up, if you will. By designing or synthesizing antibiotic compounds, we are trying to stop the germs from the top down. We'll probably never win that way. We have our own bottom-up-designed antibacterial arrangement--our immune system. Of course, maybe one day we will come up with antibacterial compounds that change with time the way germs do as they reproduce. In the meantime, let's save the antibiotics for jobs where they're really needed--that is, when we're really sick. The more we can rely on ordinary soap, solvents, and our own immune systems, the less we'll have to rely on lucky finds in nature to beat the germs.
See more of Bill Nye's answers to questions about science.


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