Download Define of bacteria:

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Bacteria
Define of bacteria: Bacteria are unicellular microscopic organism and have a cell
wall. Some bacteria have flagella ,fimbria, capsule and spore. It contain nucleus no
unclear membrane and nucleoli. They are multiply by binary fission.
Classification of bacteria:
1.Cocci.
A)Gram positive Cocci.
i)Strepto coccus
ii)Staphylo coccus
iii)Pneumo coccus
B)Gram negative Cocci.
i)Neisseria gonorrhoae
ii)Neisseria meningitides
2)Bacilli.
A)Gram positive bacilli.
i)Clostridium. (Tetani,Botulism)
ii)Corynebacterium diphtheria.
iii)Bacillus anthrax
B)Gram negative bacilli.
i)Escherechia coli
ii)Salmonella Typhi
iii)Vibrio cholera
iv)Proteus Vulgaris
C)Acid first bacillus
i)Mycobacterium tuberculosis
ii)Mycobacterium leprae
D)Flexible Spirochetes.
i)Leptospiral
ii)Treponema
E)Mycelial Bacteria.
i)Streptomyces
ii)Actinomyces
A. Morphological classification
1. Cocci: they are rounded. On the basis of their arrangement they are further
classified into
i) Monococcus: They remain single.
ii) Diplococcus: They remain double.
iii) Streptococcus; They remain in chain form.
iv) Staphylococcus: They remain in cluster.
2. Bacilli: They are elongated rod like bacteria, e.g.- E. coli.
3. Spirochaetes: They are spiral in shape, e.g.- Treponenta pelidutn.
4. Vibrio: They are comma-shaped, e.g. - Vibrio cholerae.
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B. On the basis of gram stain:
i. Gram positive bacteria.
Example — Steptococcus, Clostridium (Tetani, weichi)
ii. Gram negative bacteria.
Example — Neisseria gonoriae, E. coli, Salmonella typhi.
C. On the basis of acid fast staining
(i) Acid fast. Example — Mycobacterium tuberculosis.
(ii) Non acid fast. Example — Streptococcus.
D. On the basis of oxygen requirement: Bacteria can be into following groups on O2
requirement:
i. Obligate aerobe.
Example Pseudomonas, Mycobacterium tuberculosis.
ii. Facultative anaerobe: Grows with or without O2
Example Staphylococci, E.Coli.
iii. Obligate- anaerobe: Grows only in absence of O2. They cannot live in the
presence of O2. Example Clostridium species.
iv. Micro-aerophilic: Grow in low oxygen concentration
Example Helicobacter pylori, Campylobacter jejuni.
On the basis of O2 requirement are divided in to 4 type1. Facultative anaerobe:- Most of the bacteria can grow both in aerobic and
anaerobic condition.
2. Strict anaerobe:- They can not survive in presence of O2. Ex Clostridium
tetani
3. Strict aerobe:- They can not survive without O2. Ex Mycobacterium
tuberculosis
4. Microaerophils:- Growing at low amount of O2
E. On the basis of spore formation.
(i) Spore forming bacteria.
Example — Clostridium species, Bacillus species.
(ii) Non-spore forming bacteria.
Example — Staphylococcus aureus, streptococcus pyogenes
F. On the basis of temperature:
(i) Psychrophilic Bacteria: Grow best at low temperature (15-20°C)
(ii) Mesophilic bacteria: Grow best at body temperature (30-37°C)
(ii) Thermophilic bacteria: Grow best at high temperature (50-60°C)
G. On the basis of Capsule:
i. Capsulated. Ex. Staphylococcus
ii. Non-capsulated bacteria. Ex. Neisseria
H. On the basis of Motile:
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i. Motile bacteria. Ex- Escherichia coli
ii. Non-motile bacteria. Ex- Shigella
I. On the basis of Toxicity:
i. Exotoxin. Ex- Streptococcus, Staphylococcus
ii. Endotoxin: Ex- Vibrio cholera, E.coli
J. On the basis of flagella:
i. flagellated bacteria
ii. Non flagellated bacteria
K. On the basis of Cell Wall:
i. Lacking cell wall- Mycoplasma and Ureaplasma,
ii. Having cell wall- All other bacteria of medical importance
L. On the basis of Habitat:
i. Obligate intracellular- Rickettsia, Coxiella and Chiamydia.
ii. Free-living- All other bacteria of medical importance.
M. On the basis of Shape:
i. Cocci- Spherical (most), lanceolate or bean shaped,
ii. Bacilli (rods)- Straight, curved, helical or spiral.