How big are bacteria?
A dozen bacteria can ride on a speck of dust and a colony of millions can thrive in the smear of a greasy fingerprint. A gram of good topsoil may be the home of ten million bacteria. Countless numbers of these midgets of the plant world swim in every thimbleful of river water and millions more crowd in every dewy leaf. We need a special unit to measure the size of tiny living things and the most powerful of microscopes to get a glimpse of them.
Billions of bacteria make their homes in your body. You are host to more of these midget plants than there are people in the world, more varieties of bacteria than there are nations in the world. Once in awhile, a hostile bacterium invades your body, causing sickness. The vast majority are your servants. These friendly bacteria aid digestion, fight invaders and perform such vital duties that you could. not live without them.
In the teeming world of bacteria there are the whales and the mice. But the majority of the vast horde fall midway between the giants and the midgets. Bacteriologists assume the average sized bacterium to measure about one 25,OOOth of an inch though few bacteria are exactly the average size. This microscopic scale of life calls for its own unit of measurement.
Scientists tend to use the metric system of tens as a standard for their units and the tape measure of the bacteria world is taken from the millimeter, which is one thousandth part of a meter. The micron is one thousandth part of a millimeter and this tiny unit is the basis for measuring the tiny bacterium. You can get an idea of its size by comparing it with a hair of your head.
The hair is about 60 microns in diameter which is just about as long as a row of sixty average sized bacteria.
The majority of bacteria measure about one micron in diameter. The average fellow may be five or ten times as wide as some of his small cousins. Some of the giant bacteria are 15 to 25 microns wide. Bacteria come in assorted shapes. Some are round balls, some sausage shaped, some are long threads and others have fine, trailing streamers. Packed together in bulk, it would take about a trillion bacteria of assorted sizes to fill a thimble. A few of these midgets prey on plant and animal tissues, causing diseases. Others help the vital processes of plant and animal tissues. Countless others toil in the soil, in the air and in the water. Without them life on earth would be impossible.
Without bacteria in the soil, there would be no decay. The land would soon be littered with sewage and corpses. The purest lake would be murky without bacteria to break down its debris into simple chemicals.
There would be no nitrates or other chemical foods for the plants: As the plant world perished, we should soon run out of food and oxygen.