Please give 3 examples of helpful bacteria and 3 examples of harmful bacteria:

Bacteria are very small single cell orgasms. They are
among the smallest living beings measuring from 0.3 to 2.0 microns in diameter. Some
scientists classify bacteria as plants while others classify in a separate group of
living beings which are neither plant of animal.

There are
thousands of different kind of bacterias. Most of these varieties are harmless to human
beings. Some varieties are harmful, while still others are helpful to humans. The common
varieties of bacteria that are useful to humans include various types of antibiotics.
Some bacterias that live in human intestine help in digestion. Other bacteria in human
intestine produce some vitamins. The process of fermentation used for wine making,
cheese processing, and many other food, relies on use of specific
bacteria.

Harmful bacteria can cause diseases such as
cholera, leprosy, tuberculosis and typhoid. Other bacteria produce toxins which cause
diseases such as diphtheria, scarlet fever and tetanus. A form of bacteria that develops
in preserved food produces toxins that cause form of food poisoning called
botulism.