1. Bacterial Cell Wall
2. CELL WALL The cell wall is the outer most layer of the cell. In many cases the cell wall comes in direct contact with the environment. Function • Protection of the cell. • Maintains the shapes of the cell. • Maintains the osmotic integrity of the cell.
3. • Assist some cells in attaching to other cells or in eluding antimicrobial drugs. • Not present in animal cells, so can target cell wall of bacteria with antibiotics. • Providing attachment sites for bacteriophages. • Play an essential role in cell division. • Providing a rigid platform for surface appendages- flagella, fimbriae and pili.
4. Bacterial classification
5. Peptidoglycan • Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the cell membrane of most bacteria forming the cell wall. • The sugar component consists of alternating residues of β-(1,4) linked N-acetylglucosamine and N- acetylmuramic acid. • These subunits which are related to glucose in their structure are covalently joined to one another to form glycan chains.
6. • Attached to the N-acetylmuramic acid is a peptide chain of three to five amino acids. The peptide chain can be cross-linked to the peptide chain of another strand forming the peptidoglycan.
7. Peptidoglycan structure
8. Peptidoglycan structure
9. Gram Positive Cell wall • Usually thick, homogenous, composed mainly of peptidoglycan. • It accounts for 50-90% of the dry weight of the cell wall. • Contain large amount of teichoic acids (polymers of glycerol or ribitol joined by phosphate group).
10. Special components of Gram positive cell wall Teichoic acid
11. Teichoic acid • Teichoic acids are connected to either peptidoglycan or to plasma membrane lipids. • Absent in gram negative bacteria. Function of Teichoic Acid: . Antigenic determinant (receptor molecule for bacteriophages). . Participate in the supply of Mg to the cell by binding Mg++ . Regulate normal cell division. For most part, protein is not found as a constituent of the G+ cell wall except M protein on group streptococci.
12. Gram Negative Cell Wall • Multi layered and more complex than Gram positive cell walls. • Peptidoglycan of gram negative bacteria is thin and comprises only 10% or less of cell wall. • Outer membrane lies outside the thin peptidoglycan layer. • Most abundant protein is Braun’s lipoprotein.
13. Special components of Gram negative cell wall
14. Periplasm: • The region between the cytoplasmic membrane and the outer membrane is filled with a gel-like fluid called periplasm. • In gram negative bacteria, all secreted proteins are contained within the periplasm, unless they are specifically translocated across the outer membrane. • Periplasm is filled with the proteins that are involved in various cellular activities, including nutrient degradation and transport.
15. Outer membrane • Peptidoglycan layer is surrounded by outer membrane in the gram negative bacteria. • Its outside leaflet i
All-domain Anomaly Resolution Office U.S. Department of Defense (U) Case: “Eg...
BACTERIAL CELL WALL.pptx
1. BACTERIAL CELL WALL
NAME : NISHA R
REG NO : BP211511
SUBJECT : GENERAL MICROBIOLOGY AND MICROBIAL DIVERSITY
DATE : 15/11/2021
TITLE : BACTERIAL CELL WALL OF GRAM POSITIVE AND GRAM
NEGATIVE BACTERIA
SUBMITTED TO : Dr.P. SARANRAJ
2. GRAM POSITIVE BACTERIAL CELL WALL
Cell wall is present outside the Cell membrane.
Cell wall acts as a backbone of cell and gives shape and rigidity to the cell.
Bacterial cell wall confers Osmotic protection from toxic substances and Gram staining characteristics.
The cell walls of almost all the bacteria is made up of Peptidoglycan, also called murein or mucopeptide cell wall. It is found only
in Prokaryotes
The Peptidoglycan consists of two components viz., (i) Peptide portion which is composed of Amino acids connected by Peptide
linkages and (ii) Glycan or Sugar portion.
3. The Glycan portion, which forms the backbone of Peptidoglycan, is composed alternating
units of amino sugars N-acetyl-glucosamine (NAG) and N-acetyl-muramic acid (NAM)
joined together by β-1,4 glycosidic linkages.
The peptidoglycan chains are laterally liked by short chains of four amino acids which are
attached to NAM residues. The four amino acids of this Tetrapeptide are D-alanine, L-
alanina, D- glutamic acid and L-lysine.
The Tetrapeptide chains are also interlinked by a Peptide bridge (Polypeptide linkage
chains).
5. A Model Of The Constitution Of Gram Positive
Bacterial Cell Wall
6. Teichoic acid, an acidic polymer consisting of a Carbohydrate (e.g., glucose), Phosphate and
Alcohol is found in cell walls of Gram +ve bacteria. There are two classes of Teichoic acids.
They are (i) Wall teichoic acid and (ii) Lipoteichoic acid.
Teichoic acid has several functions such as binding metals, action as receptor sites for some
viruses and maintaining cells at low pH to prevent degradation of cell walls by self-produced
enzymes.
7. GRAM NEGATIVE BACTERIAL CELL
WALL
The cell walls of Gram negative bacteria are much more complex.
The peptidoglycan layer of Gram negative bacteria is very thin making up only 10 % or less
of the cell wall.
The Outer membrane is a thin, bilayered structure consisting chiefly of Phospholipids,
Proteins and Lipopolysaccharides (LPS).
8. The Outer membrane serves as a barrier to prevent the escape of important enzymes from the
Periplasmic space.
The permeability of Outer membrane to nutrients is provided by proteins called Porins which form
channels in the membrane thought which substances of hydrophilic nature and low molecular
weight can diffuse.
The space between the Cytoplasmic membrane and the Outer membrane is called Periplasmic
space.
The Periplasmic space prevents the entry of various chemicals that could damage the cell. It also
acts as main surface antigen in cell wall.
