The cell wall of some bacterial cell is surrounded by a gelatinous (slime) layer. This is called capsule or slimy layer. â. A capsule is present in ...
Antony Leeuwenhoek (1 683) of Holland observed first time in rainy water and named Animalcules. F.J.Cohn and Ehrenberg first of all coined the name included in Schizomycetes division of Thallophyta Steiner placed Bacteria in group of Protista. “Bergy” wrote a book “Manual of Determinative group “Prosophyta”. Leeuwenhoek is considered as a father “Bacteriolgy” Louis Posteur of disease”. First of all Rober Koch cultured Bacteria artificial y Tuberculosis disease. All the prokaryotes placed in placed in group Monera by Whit akar. Linneus placed bacteria in Vermes.
by
‘Bacteria’ Oswalt Tippo.
Microbiology
for them. Bacteria have been
” and placed bacteria in a separate “Germ theory
proposed and discovered bacteria of cholera
and
FORMS OF BACTERIA 1.
2. 3. 4.
Bacil us :Most of the bacteria comes in this category. They are rod shaped. They are of the fol owing types-They are found in a chain. Example Streptobacil us by mucous sheath or covering. It is cal ed -When only one rod like structure is present in the bacterium. This is Single Bacil us common. - When they are found in pairs. Diplobacil us Spiril um :This type of bacteria are in the form of helix or coil. Example - Spirochaeta, Trapanoma. Comma shaped :These bacteria are comma shaped. Example:- Vibrio. Cocci: They are spherical or globular. They are smallest bacteria, They are non motile. Flagella are absent. They may be fol owing types -
Monococcus Diplococcus
subtil s Zooglea.
Example - Nesseria. St r e pt o coccus Stephylococcus:S. alvus Sarcinae Multiple form bacteria They change their shape according to the change of medium
Subtil s
is sur ounded
.
Example -
They are found in cubical forms/ packets of 8, 64 or more. Example— -
Diplococ us forms.
:-They are found in the form of chain. They are found in a groups or bunches. :-
. B.
most
- Monococ us type of bacteria live alone - e.g. Micrococ us. :- In which two coc i are always found in a pair. pneumoniae :- In this group bacteria are found in group of four cel s or tetrahedral
Tetracoccus
5.
Bacil us
Example –
Streptococ us lacti Example-Staphylococ us aurus,
Sarcina e.g. Rhizobium.
Printed by BoltPDF (c) NCH Software. Free for non-commercial use only.
.
MICROBIOLOGY Size of Bacteria : Bacteria are extremely small in size ranging from 0.5 10 m in length. Smallest bacteria Micrococcus Largest bacteria Begiota and Spirilium
to 1.5 in diameter and about 0.5 to
Motility of Bacteria :Bacteria are motile as well as nonmotile. Flagella are present in motile bacteria and absent in non motile bacteria. Flagella are found in bacteria which is different from eukaryotic flagella. Length of flagella is 4-5 m and diameter is 120A 0 of bacteria. The arrangement of (9+2) microtubules are absent in flagella of bacteria. In place of this arrangement only 1 or 3 microtubules are present which is present in scattered form. Microtubules which is present in flagella of bacteria are made up of flagellin protein. These flagella are stained by Leafson stain. The basal granules of these flagella is hook like. This is called basal hook. Number and Position of Flagella :On the basis of number and position of flagella, the bacteria are divided into following types 1. Atrichous :When the flagella is absent which is called Atrichous. Example :- Micrococcus ; Pasteurella. 2.
Monotrichous :When there is only one flagellum found on one end of the bacterium. Example - Vibrio, Thiobacillus.
3.
Lophotrichous :When there is a bunch of flagella on one end of bacteria. Example – Salmonella
4.
Amphitrichous :When a tuft or bunch of flagella is attached at either ends (on each ends). Example – Spirillium and Nitrosomonas.
5.
Peritrichous :When the flagella are found on whole body of the bacteria.
Escherichia coli ; Clostridium.
Structure of Bacterial Cell The following structures are found in bacteria. 1.
3
Capsule - [Barrier layer] :The cell wall of some bacterial cell is surrounded by a gelatinous (slime) layer. This is called capsule or slimy layer. A capsule is present in bacteria, are known as capsulated bacteria. Such bacteria have power of infection. They are pathogens. The secretion of capsule is by the cell wall in the form of outer cellular layer. Capsule is made up of unknown polysaccharides and polypeptides. This capsule is highly developed in pathogenic bacteria and it is protected from the W.B.C. of man.
Printed by BoltPDF (c) NCH Software. Free for non-commercial use only.
