The Useful of Bacteria

There are two kind bacteria if see from the uses for human, benefit and disadvantage for human. Most of us think of bacteria as "germs" or microorganism, unseen threats to our health and welfare. But for each of the few disease-producing kinds which can live in the human body, there are hundreds of others upon which we depend for our very existence. Bacteria help us digest our food. Plant will die if no bacteria to convert leaf or other organic matter to humus.

Most kinds multiply by simply splitting in two: each bacterium dividing into two equal "daughter" bacteria every 20 or 30 minutes, under favorable conditions. Though microscopic in size, they can multiply so fast that, after a day and a half, the billions of offspring of a single one would load a long freight. Under unfavorable conditions, some kinds form thick-walled spores which can withstand prolonged drying, extreme cold, and even boiling; and may lie inactive for days or even years.

All animals depend upon plants, directly or indirectly. Plants depend upon the fertility of the soil, which in turn depends upon bacteria. Inconceivable numbers of them inhabit the soil -- roughly a billion per teaspoonful -- where some convert plant and animal remains into humus and plant food, and others make the minerals in the soil available as plant food. All decomposition and decay in the dead bodies of plants and animals are caused by bacteria and their close relatives: molds, fungi and yeasts. Our huge garbage dumps are decomposed by them. Our modern methods of sewage disposal employ speeded-up bacterial action to rapidly break down and oxidize household and industrial wastes.

Some of plant reside a kind of bacteria, Nitrogen in the form of nitrates is an essential plant food frequently lacking in soils. Nitrogen from the air is inert and difficult to change and combine with other substances, but certain bacteria have the rare ability to absorb it and change it into forms which other plants and animals can use.

Fermentation, as when wine and cider turn into vinegar, is caused by bacteria. Of hundreds of different kinds, a few of the common bacteria are those used to make rye bread, sauerkraut from cabbage, pickles from cucumbers, silage from corn, linen from flax, glycerin, citric acid, lactic acid, and dairy products.

Fresh warm milk is an ideal food for many kinds of bacteria, especially the common one which causes milk to sour and curdle. Cream so soured and ripened is easily churned into butter. Cottage cheese is made from sour milk. Most cheeses are made from curds produced by treating milk from cows, sheep or goats with "rennet", a digestive ferment. The ripening, and the different textures and flavors, are accomplished by various pure cultures of bacteria and molds which are added to the curd as "starters", depending also upon special conditions of air, moisture and temperature. Some extremely hard Italian cheeses contain little water and are correspondingly slow to ripen. "Soft" cheeses contain more water and ripen more rapidly. The blue-green mold of Roquefort is due to powdered bread mold sifted into the curd. The holes in Swiss cheese come from gas generated by bacteria.