Bacteria
Prokaryotic unicellular micro organism wich divided by binary fission are do not present Chlorophyll.
Size - size various from 0.5 to 15 micrometer length and 0.2 to 2 micrometer in diameter.
Anatomy of the Bacteria
The outer layer or cell envelope of a bacterial cell consist of 2 components
1 - A Rigid cell wall.
2 - Cytoplasmic or plasma membrane.
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Gram positive and gram negative bacteria |
Cell wall enclose the Protoplasm comprising of Cytoplasm
( a ) Ribosome.
( b ) Inclusion granules.
( c ) chromosomes.
( d ) Single circular Chromosome of DNA.
Some bacteria in addition may additional structures such as -
1 - Protective gelation covering outside the wall known as Capsule.
2 - some bacteria passes filamentous appendages flagella fimbria with protrude from cell surface.
Cell wall - It is tough and rigid structure surrounding the bacteria like a Shell.
- The cell wall is to 10 to 20 micrometer in thickness rigidity upon bacteria in addition to giving protection to cell against in osmotic damage.
- It is elastic are poroud are is freely permeable to solute molecules of less than 10,000 molecular weight.
- The cell wall taken part in all division forming an in growth from the cell wall.
- The nucleotide component of all wall passes largest side for antibiotics ,lysosome,a bacteriophages.
STRUCTURE OF CELL WALL
The chemical structure of cell wall of gram positive and gram negative bacteria differ considerably,it is comparatively simple in gram positive than that of gram negative bacteria the rigid part of all cell wall is Peptidioglycan.
Composition of cell wall
1 - Peptidioglycan
It is the principal structure components of cell wall of gram positive and gram negative.It is more abundant in gram positive bacteria.It links involves between the terminal residue to peptide side chain are adjoining side chain.
2 - AutoLysin
All bacterial cell wall passes enzymes called autolysin wich can hydrolyse their own cell wall substance this capacity of autolysin to dissolve the peptide glycine is essential for cell growth all repation and prolation.
Functions of cell wall
( a ) Supportive
Mechanical support to membrane.
( b ) Protective
Protect cell membrane from inimical efforts.
( c ) Reproductive
Essential for life cells are divided by forming wall to separate daughter cells.
( d ) Preventive
It prevent osmatiys of cell.
Two special structure of gram positive cell wall
1 - Teichoic acid ( TA )
The water soluble polymeres of glycerols two type of TA are recognized are present only in gram positive bacteria .
( a ) wall teichoc acid - It lack in some gram positive bacteria.
( b ) Membrane TA It's present all gram positive bacteria.
Functions of TA ( Teichoic acid )
- TA are the seat of bacterial surface Antigens in gram positive bacteria.
- They bind in Magnesium ion for gram positive cell.
- They play a role in normal function of cell envelops.
2 - Polysaccharides
Gram positive cell wall contain neutral sugar like galactose and acidic sugar like gluconic acid.sugar exist of submit of polysaccharides in cell wall.
Three special components of gram negative cell wall
( 1 ) Lipoprotein
Unusual lipoprotein molecules cross links the outer membrane and peptide glycane layers.
( 2 ) Outer membranes
It's phospholipid bilayer in with phospholipid is on the outer leaflet of cell wall.this membrane is mostly replaced by polysaccharides it serve as a protective envelop for protein.
( 3 ) Lipopolysaccharide
It. Is a complex liquid to which is attached lipid A-[ B - hydroxy myrastic acid is a unlike to this lipid ] with as always present.
PROTOPLAST
Cell wall of many bacteria when digested enzymatically have a spherical structure known as free protoplast.after digestion of gram positive bacillus is bound only by Cytoplasmic membrane.protoplast may enlarge but cell do not multiply in absence of cell wall.
SPHEROPLAST
When the cell wall become weaker with is obtained by Enzymatic digestion of gram negative bacilli the gram negative bacteria with damage or destruction of cell wall is called spheroplast.
L-Form - These are abnormal form in culture of coccai bacilli and viruses.The lar rigid cell wall and so not regular.They are soft protoplasmic bodies.spherical in shape.
Size - They are 0.1 to 10-20 micrometer in diameter on agar L-Form show dried appearance with a thick centre.
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| Bacterial cell wall |
SECTION OF BACTERIAL CELL
Cytoplasmic membrane - It is a thin 5-10 nm thick elastic semipermeable layer and lies beneath the cell wall separating it from the cell cytoplasm it has lipid bilayer structure.
It is a polycochemical barrier between cell wall and cytoplasm.it is a physical and metabolic barrier between external and internal of bacterial cell.
1 - TRANSPORT
( A ) Active transport
It is a site of numerous enzymes involved in at of selective Nutrients.It is impermeable to macromolecules and Ionised substance.
( B ) Passive transport
It acts as a semipermeable membrane through inwards and outwards passage of water and PT of small molecular lipid soluble solutes.
2 - CONCENTRATION
It's also concentrate sugar , Amino acid and phosphates.It also contains cytochrome,oxidase, Enzymes of tricarboxylic acid cycle and polymerase Enzymes necessary for synthesis of cell wall.
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