Cell wall of gram-positive bacteria

This slideshow contains the brief description of the structure of the gram positive bacteria.

1. PRESENTED BY- ABHINANDAN KUMAR SEC- A 1 -T 1 ROLL NO- 04 B.Sc.( Hons .) Agriculture QUANTUM UNIVERSITY, Roorkee FUNDAMENTALS OF MICROBIOLOGY CELL-WALL OF GRAM-POSITIVE BACTERIA

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). GRAM-POSITIVE CELL-WALL

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: Gram positive Gram negative Why they are named Gram-Positive?

4. Gram-Positive Cell-Wall structure

5. Special components of Gram-Positive Cell-Wall 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 .

6. • 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). PEPTIDOGLYCAN

7. • 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.

8. Peptidoglycan structure

9. • 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. TEICHOIC ACID

10. Teichoic Acid structure

11. Cytoplasmic lipid membrane. Thick  peptidoglycan  layer. Peptidoglycan chains are cross-linked to form rigid cell walls by a bacterial enzyme  DD- transpeptidase . Characteristics of Gram-Positive Cell-Wall

12. 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.

13. Classification of Bacteria with Gram-Positive Cell-Wall

14. Comparison