Bacteria are found in everywhere like in water, in air etc. On the basis of shape and form bacteria are of four types round, rod-like, spiral and comma shaped.
Bacteria are found in groups and even in beaded form. Bacteria are unicellular microscopic organism. A distinct nucleus is absent in bacteria, however, only a single large, circular molecule of DNA is present. It is not bounded by nuclear membrane. Bacterial cell covered by a cell wall. A few bacteria have an additional slime capsule around their cell wall. Some bacteria have one or more thread like flagella, which helps them in moving.
Some bacteria are autotrophs while most are heterotrophs. Bacteria, which live on living things for nutrition, are called . The parasitic bacteria cause diseases in plants and animals and are known as pathogenic bacteria. Bacteria are transmitted from one living organism to other through touch, air, contaminated water and food, insect and through other organisms.
Bacteria plays very important role in our lives. They are beneficial as well as harmful for us. Bacteria are used in medicine for example to make antibiotics like streptomycin, tetracycline and tobramycin. These antibiotics destroy harmful bacteria present in our body. Bacteria also used for industrial and commercial purposes.