If you ask someone which creature is most important on the earth, we may get different answers, man, plants other animals and so on. One cannot suddenly think of those minute microscopic creatures that are invisible to the naked eye. A wide range of those microscopic organisms usually referred as micro organisms include bacteria, fungi, viruses, algae and protozoans. Though some of them are harmful many of them are useful and very important for survival of life on
this planet. Bacteria are a group of microscopic organisms which are present everywhere omnipresent and omnipotent and are considered to be the most abundant microorganisms on earth. Different types of bacteria are included under Archaebacteria, Eubacteria and Cyanobacteria under kingdom Monera of Whittaker’s Five Kingdom classification.
Important persons in microbiology and bacteriology:
1) Leewen hoek, Louis Pasteur and Robert Koch – foundation for
2) Louis Pasteur – developed technique of pasteurization and preparation of vaccine.
3) Anton Van Leewenhoek – discovered bacteria and called them animalcules.
4) Anton Van Leewenhoek – Father of Microbiology.
5) Louis Pasteur – Father of Bacteriology.
6) Ehrenberg – coined the term Bacteria.
7) Louis Pasteur – showed that bacteria are chemical factories that bring changes in nature.
8) Koch – Germ theory of disease.
Bacteria - Key concepts:
1) Escherichia coli bacteria are present in human intestine.
2) Rhizobium is present in the nodules of roots of leguminous plants.
3) Morphology of Bacteria:
The size of bacteria ranges from 2.0 to 5.0μm in length and 0.5 to 1.0 μm in breadth.
Shapes of bacteria may be
Cocci – spherical
Bacilli – Rod shaped
Spirillum – helical rods (more than one complete twist)
Vibrios – comma shaped (less than one complete twist)
Pleomorphic – bacteria change their shape depending on the type of
environment or available nutrients.
Spirochaets – flexible spiral bacteria (slender long an cork-screw
Filamentous – long thread like or filament like chains
Bacteria cells may be single or in groups like
Monococcus – single spherical cell
Diplococcus – a pair of spherical cells
Tetra coccus – a group of four spherical cells
Streptococcus – linear chain of spherical cells
Staphylococcus – bunches of spherical cells
Sarcinae – eight spherical cells arranged as a cube
Mono bacillus – single rod shaped cell
Diplo bacillus – a pair of rod shaped cells
Strepto bacillus – chains of bacilli appearing like straws