Bacteria and viruses

Bacterium is the simplest and the smallest form of plant life. They exist in air, water and soil, and in living and dead animals and plants. One teaspoon of rich soil is home to more than 100 billion bacteria. These microbes recycle leftovers of everything else. Bacteria are about two billion years old, and nowadays nothing can live without them. While some of them are pathogens or germs, the others work to breakdown or convert matter into nutrients that can be used by organisms for food. Bacteria in our intestines help us digest our meals.

Bacteria clean up our environment by feeding on toxic wastes, petroleum, and sewage. Some bacteria make nitrogen available to plants. Industries can culture microorganisms to produce medicines, pesticides, solvents, and even to separate metals from ore.

Microorganisms secrete enzymes used in fermenting beer, wine, cheeses, breads, and many other foods.

A virus is any of various poisonous elements, smaller than bacteria, causing the spread of infectious diseases.

Viruses consist usually of a central part containing nucleic acid, surrounded by a coat of protein, or of protein and lipid. The nucleic acid is: DNA or RNA in viruses attacking animals; RNA in viruses attacking plants; usually DNA in bacteriophages.

Viruses replicate within the host’s cells forming new virions which invade further cells of the host. Viruses can only replicate intracelluarly, so they can not be cultured in a nonliving medium.

The nucleic acid of the virus takes control of the nucleus in the host cell. During this process the cell may be destroyed or may produce toxins which cause clinical disease.

Viruses can be spread either by droplet infection, personal contact or biting insects.

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