It was Anton Van Leuwanhoek in 1683 who observed bacteria
with the help of his self constructed compound microscope. Bacteria are found
everywhere in air, water, soil, food in living organisms such as the intestines
of man and animals, on dead decaying organic matter, etc.
Bacteria are single celled organisms or made up
of chains or clusters of similar cells. Bacteria has no distinct nucleus. The nucleus is
not bounded by a nuclear membrane, i.e. bacterial cell is prokaryotic.
Chromatin material is present in the central region. Nucleolus is absent.
Bacterial cell have a cell wall composed of mainly chitin. A thin layer called
capsule surrounds the cell wall.
Mitochondria and chlorophyll are absent. Reserve food is glycogen. On the
basis of general shape four main types of bacteria are recognized
They are: 1.
Coccus
2. Bacillus
3. Spirillum
4. Vibrio
2. Bacillus
3. Spirillum
4. Vibrio
