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Q & A: Killing germs

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Q:
How are germs killed?
- Chris
A:
"Germs" is a rather informal, collective name for anything that makes us sick and which can reproduce (to distinguish them from poisons, for example). Viruses and bacteria qualify as "germs". The word comes from the Latin word for "seed".

Since germs have been so harmful for so long, people have come up with lots of different ways to kill them. Some germs are more difficult to kill than others, and people argue about whether to call some germs (viruses in particular) alive to begin with. But viruses can be destroyed or rendered inactive in other ways.

Hereís a short and probably incomplete listing of ways to kill germs:

1) Heat them up. Many germs fall apart when they are too hot, and perhaps more so when they are too hot and wet. Boiling water kills most germs in it and makes it much safer. Cooking food also kills the germs in it. Canned food is usually prepared at high temperature to make sure that live germs are not left to multiply in the can while it sits on a shelf for months or years.

2) Poison them. Bleach is a common ingredient in household cleaners and is a potent toxin for just about anything living, germs included, because it reacts with many different molecules and changes them. Antibacterial agents, fungicides, and other cleaning agents (like ammonia) do a good job of killing germs. These techniques are good for germs that arenít inside anyoneís body -- you can apply strong chemicals to sterilize surfaces as long as you donít ingest the chemicals or breathe too much of the fumes. Warning -- do not mix cleaning substances! They can react and release poisonous gases.

3) Antibiotics disrupt bacterial functions. Many antibiotics break down the cell walls of bacteria, making the bacteria fall apart. These drugs have to be carefully selected to poison only bacteria while leaving the cells of the person unharmed. Bacteria can evolve resistance to antibiotics, however, rendering them useless over time, particularly if they are overprescribed and/or used improperly. Antibiotics do not kill viruses, however. Antibiotics may kill off some helpful bacteria in your intestines, and so taking an antibiotic for a viral infection may leave you sicker than before.

4) A new class of drugs, antivirals, interferes with the cycle viruses undergo to reproduce themselves. Itís not clear whether the viruses are actually "killed", just that they fail to reproduce.

5) Irradiate them with light or other radiation. Ultraviolet light is really good at killing germs -- some germs donít last long on sunny, hot surfaces. Some food is irradiated with radioactive sources, which also does a good job of killing germs.

5) Dry the germs out. Some germs die when dehydrated. Others may start activity again when re-hydrated.

6) Some germs may die when frozen. Sharp ice crystals poke holes in cell walls, destroying them. Other germs are just slowed down when put in the freezer and may come back to life when thawed.

7) This oneís of entertainment value perhaps, if nothing else: some viruses attack bacteria, killing them in the process. Of course trading one germ for another may not help your situation.

8) Your body kills germs all the time. Your skin and mucus membranes has an enzyme called lysozyme which breaks down the cell walls of bacteria. Your immune system works in several different ways. Some germs are engulfed by white blood cells. Others get antibodies stuck to them, disabling them.

9) Why kill them at all? Usually just washing stuff off with soap and water gets rid of them plenty well, and doesnít involve nasty chemicals or other hazardous, expensive methods.

Tom

(published on 12/03/11)

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