Question

In your own words, describe in two paragraphs, the following bacterial cell wall characteristics related to gram-positive strains and gram-negative strains: (a) chemical composition, (b) resistance to phagocytosis, and (c) decolonization by alcohol during Gram-staining (d) sensitivity to antimicrobial agents.

Answer 1

(a) The chemical composition of the cell wall of the gram positive bacteria is thick including the peptidoglycan layer and this layer is thin in gram negative bacteria. The layer of lipopolysaccharides is thick in the gram negative bacteria as compared to the gram positive bacteria. Techoic acid is present in Gram+ bacteria and absent in Gram - bacteria.Lipoprotein is high in gram- bacteria and less in gram+ bacteria.Murein content is high in Gram+ bacteria as compared to gram- bacteria.

(b)The presence of lipopolysaccharides in the walls of gram- bacteria makes them resistant to phagocytosis as compared to the walls of the gram + bacteria which are susceptible to phagocytosis.

(c) The Gram + cells turn purple or violet when stained with crytal violet. They retain color after washing with alcohol.Gram -cells stain red or pink with crystal violet stain. They lose color after washing with alcohol.

(d)Gram - bacteria are more resistant to antiobiotics as compared to gram + bacteria which are more susceptible.