Introduction-Cell wall and functions Gram +ve and -ve cell wall Bacterial cell wall - structure Peptidoglycan-Composition and Structure Types of polysaccharidesBacterial cell wall Functions of polysaccharides in Bacterial cell wall

2. Introduction
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
• Assist some cells in attaching to other cells or in eluding antimicrobial
drugs.
• Providing attachment sites for bacteriophages.
• Play an essential role in cell division

3. 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).
Special components of Gram positive cell wall is Teichoic acid
• Teichoic acids are connected to either peptidoglycan or to plasma membrane
lipids. • Absent in gram negative bacteria.
Functions 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
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.

9. Types of Polysaccharides in bacterial cell wall
1. Bacterial Glycoproteins are lipopolysaccharides (LPSs) and
capsular antigens which are attached by lipid anchors (lipid A
or diacylglycerophosphates) in gram-negative bacteria
2. Membrane-Derived Oligosaccharides -e also known as the
osmoregulated periplasmic glucans (OPGs) --MDOs are a
heterogeneous family of closely related, highly branched
oligosaccharides containing glucose as the sole sugar. They
are substituted with sn-1- phosphoglycerol,
phosphoethanolamine, and 0-succinyl ester residues

10. 3.Lipopolysaccharide -made up of a lipid and a
polysaccharide which are joined together by a covalent
bond.In Gm –ve bacteria-Lipopolysaccharide (LPS)
comprises of three parts: (i) “O” antigen, (ii) core
polysaccharide, and (iii) lipid A. The sugars commonly
present are heptose and 3-deoxy-D-mannooctulosonic acid
4. Lipo oligosaccharides - glycolipids which are present in
the outer membrane of certain types of gram-negative
bacteria.
5. Capsular Polysaccharide - The capsular polysaccharide
constitutes the outermost layer of the bacterial cell and
mediates its direct interaction with the environment
Accessory polysaccharides consists of Sugars like teichoic
acid(Glycerol or Ribitol),Rhamnose,Glucose,Galactose or
mannose

11. Functions Of Polysaccharides in Bacterial cell wall
Importance of Glycosylation
The N- or O-glycosylation of the peptide in bacteria could induce the
host response by causing infection
Lipopolysaccharides--act as a candidate target for new antimicrobial
agents. LPS generally acts as endotoxin as it binds to the cell
receptor (CD14/TLR4/MD2) complex in monocytes, dendritic cells,
macrophages, and B cells, which thereby promotes the secretion of
proinflammatory cytokines, nitric oxide, and eicosanoids
Capsular Polysaccharide The capsular polysaccharide constitutes the
outermost layer of the bacterial cell and mediates its direct
interaction with the environment