Bacteria are the most abundant
group of microorganisms in nature. It is found everywhere on the planet,such as
hot spring,deep ocean,deserts and even thrive inside our intestine. The term
bacterium was given by Ehrenberg. The branch which is deals with
bacteria is known as Bacteriology. Unlike many organisms, bacteria have no
natural death.
- Smallest bacteria: Dialister
pneumonsintes
- Largest bacteria: Epulopiscium
fishelsoni
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| Bacteria |
General Characteristics
- Bacteria are prokaryotic organisms (Kingdom:Monera),
without cell defined organelles like mitochondria,Golgi bodies,Endoplasmic
reticulum.,etc
- Microscopic,unicellular,they may occur singly
or aggregations to form colonies.
- They posses rigid cell wall. Cell wall is
made up of peptidoglycan (Mureins) and Lipo polysaccharides.
- Absence of well defined nucleus.i.e., DNA is
not enclosed in a nuclear membrane.
- Ribosomes are scattered in the
cytoplasmic matrix and are of 70S type.
- The plasma membrane is invaginated to form mesosomes.
- Most of the bacteria are heterotrophic.Some
bacteria are autotrophic, posses bacteriochlorophyll, which is
not in plastids.Instead it is found scattered.
- Motile bacteria posses one or more flagella.
- The common method of multiplication is binary
fission.
- True sexual reproduction is lacking,but genetic
recombination occurs by conjugation ,transformation and
transduction.
Shape of Bacteria
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| Shape of Bacteria |
1.Cocci- Spherical or ellipsoidal
- Micrococci- ex:Micrococcus
- Diplococci ex:Diplococcus pneumoniae
- Streptococci- ex:Streptococcus
- Staphylococci- ex:Staphylococcus aurens
- Tetracocci- ex:Genus Micrococcus often divide in two planes to form square groups of 4 cells called Tetrad
- Sarcine- ex:Sarcina lutea
- Vibrio- ex: Vibrio chlorae
3. Spirillum- Spiral shaped
ex:Spirillum volutans
4. Other shapes Mycellium - ex: Streptomyces
- Pleomorphic- ex: Corynebacterium
diphtheriae
