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Good and bad, loss and profit from the bacteria. Very dangers bacteria also are there. Those shape little in little.

They cannot be seen through naked eye. You can see them only through a microscope.

The microbes were seen for the first time in 1677 by A.V. Leeuwenhoek through a microscope invented by him.

Therefore, they are called microbes or micro-organisms. But they help you making Yoghurt, vinegar, or bread. They make grayish-white patches on stale bread. They can spoil food, damage potato and corn and wheat. They cause rotting of clothes, shoes and wooden materials. They tiny organisms make humans and animals sick, sometimes carry them to death. And the same organisms used as a vaccine cure the sick, sometimes bring back to life. They are present everywhere, inside the body and out side, every time.

The soil water and air around us are all full of tiny organisms. We encounter them constantly but become aware of their presence only through their action. They can do all the essential functions of life. They take food, grow and reproduce to multiply rapidly in large numbers with a very short time if they found enough food, moisture and suitable temperature. These are the essential conditions for life.

Tiny organisms or microbes living in air, water or soil are called free living. Microbes also live inside plant or animal body. They get their food from their host. So they are called parasites. The microbe plasmodium lives on female anopheles mosquito and blood of man. Same microbes live in a mutually benefiting association. They are called symbiotic microbes. Microbes digesting the cellulose of leaves live in the rumen of cow, sheep, goat etc.

Microbes flourish in almost every kind of environment- hot springs, ice-cold waters, salty waters, and desert soil or marsh land. To overcome these extreme conditions of temperature, salt and dryness they form a hard water outer coat called cyst. Within this protective shell they remain inactive. When the favorable conditions return, microbes come out from their shell, multiply and repeat their life cycles.

Microbes are classified according to their structures and functions. Major groups of microbes are protozoa, fungi, bacteria and viruses. Protozoa are single-celled animals. Fungi are very small non-green plants. Bacteria are single-celled plants which may be round, rod-like or spiral in shape. Viruses are much smaller. They cannot be seen through a microscope. They can be photographed only with electron microscope. Viruses lie on the border-line of living and non-living. They become active only on entering a living body.

Microbes can be useful or harmful for humans, animals and plants. The harmful or disease causing microbes are called germs. Germs usually enter our body through the nose, mouth and broken or cut shin. When herms enter human body, white blood- cell fight and kill many of them. However, if herms get a weak part, they feed and grow there. When they multiply into large numbers, they attack healthy parts also. When germs start to grow, multiply and affected our body; it is called infection.