This document discusses the key components and characteristics of Gram-positive bacterial cell walls. It notes that Gram-positive bacteria have thick, homogenous cell walls composed mainly of peptidoglycan, which can account for 50-90% of the dry weight. The peptidoglycan layer contains cross-linked glycan chains of sugars and peptide chains, and is connected to teichoic acids and the cytoplasmic membrane. Gram-positive cell walls also contain teichoic acids that are antigenic and help bind magnesium and regulate cell division.

1. PRESENTED BY-
ABHINANDAN KUMAR
SEC- A1-T1
ROLL NO- 04
B.Sc.(Hons.) Agriculture
QUANTUM UNIVERSITY,
Roorkee

2. • Named by Dr. Hans Christian Gram in 1884.
• 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).

3. • Named by Dr. Hans Christian Gram in 1884.
• He developed a staining procedure known as Gram
Staining, which divided almost all bacteria into two
large groups.
• Depending on their retention of specific basic dyes
there are:
I. Gram positive
II. Gram negative

8. • Teichoic acids are deep-seated in the Gram-Positive cell-
wall, and are polyalcohols.
 They are strongly antigenic, but are generally absent in Gram-
negative bacteria.
• Lipoteichoic acid:– Teichoic acid linked with lipid, goes to
the cytoplasmic membrane and links the peptidoglycan to
the cytoplasmic membrane.
 They are antigenic, cytotoxic and adhesins.

9. • 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-acetyl glucosamine acid(NAG) and
N-acetyl muramic acid(NAM).

10. • Attached to the N-acetyl muramic acid(NAM) 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.
• These subunits which are related to glucose in their
structure are covalently joined to one-another to
form glycan chains.

13. • Teichoic acids are connected to either peptidoglycan or to
plasma membrane lipids.
• Absent in gram negative bacteria.
 Functions:
• 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.

15. • Cytoplasmic lipid membrane.
• Thick peptidoglycan layer.
• Peptidoglycan chains are cross-linked to
form rigid cell walls by a bacterial enzyme
DD-transpeptidase.

16. • Teichoic acids and lipoids are present,
forming lipoteichoic acids, which serve
as chelating agents, and also for certain
types of adherence.
• A much smaller volume of periplasm than
that in gram-negative bacteria.