Discuss Bacterial cell walls with regard to (a) resistance to phagocytosis, (b)

Question

Discuss Bacterial cell walls with regard to (a) resistance to phagocytosis, (b) chemical composition, and (c) decolorization by alcohol.

Read the selected scriptures and in your response to the prompt discuss how at least one of the scriptures relates to the discussion topic. For example: Leviticus has reference to mold, you can discuss how mold is classified, characteristics, and how it relates to the discussion topic.

Leviticus 14:33-53

Acts 12:23

Psalms 139:13-16

Isaiah 49:1-5     (PLEASE DO NOT COPY WORD FROM WORD FROM A SOURCE PLEASE!!!)) THANK YOU :)

Explanation / Answer

Bacterial cell wall

Chemical composition:- Cell wall is a layer present outside the cell membrane. Bacteria possess well developed cell wall and this cell wall imparts unique characteristics to the bacteria. The bacterial cell wall differs from other organisms because of the presence of peptidoglycan. Peptidoglycan is located immediately outside of the cytoplasmic membrane. Peptidoglycan is made up of a polysaccharide backbone consisting of alternating N-Acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) residues in equal amounts. It is responsible for the rigidity of the bacterial cell wall and hence defines the shape.

Based of cell wall composition, bacteria are classified into two types viz; Gram positive bacteria and Gram negative bacteria. The cell wall compositions for both Gram positive and gram negative bacteria are as follows

Gram positive bacteria:- Gram-positive bacteria have thick cell walls. The peptidoglycan layer constitutes almost 95% of the cell wall in some gram-positive bacteria. In some Gram positive bacteria, the peptidoglycan layer of contains matrix of anionic glycopolymers known as wall teichoic acids (WTAs). The teichoic acid is very important for cell shape determination, regulation of cell division, and other fundamental aspects of gram-positive bacterial physiology. The cell wall of some gram-positive bacteria can be completely dissolved by lysozymes.

Gram negative bacteria:- Gram-positive bacteria have thick cell walls. The peptidoglycan layer constitutes as little as 5-10% of the cell wall in gram-negative bacteria. Gram-negative bacteria have a unique outer membrane, a thinner layer of peptidoglycan, and a periplasmic space between the cell wall and the membrane. In the outer membrane, gram-negative bacteria have lipopolysaccharides (LPS), porin channels, and murein lipoprotein. The cell wall of gram-positive bacteria is resistant toward lysozyme attack.

Resistance to Phagocytosis:- Based on the cell wall composition, resistance towards phagocytosis s different for Gram positive and Gram negative bacteria. The chemical composition of the cell wall of both Gram positive and Gram negative bacteria is described in earlier point. Based on that the explanation for resistance to phagocytosis is elaborated.

Gram positive bacteria:- Since the cell wall of many Gram positive bacteria ispermeable to lysozyme and thus can be easily phagocytized, these cells have developed othe mechanisms such as killing the phagocyte. Many Gram-positive pathogens, secrete extracellular enzymes which kill phagocytes.

Gram negative bacteria:- Pathogenic mycobacteria have a waxy cell wall that resists attack or digestion by most tissue bactericides. Intact lipopolysaccharides (LPS) of Gram-negative bacteria protect the cells from complement-mediated lysis or the action of lysozyme.

Decolorization by alcohol:- The cell walls for Gram positive bacteria have a higher peptidoglycan and lower lipid content. Whereas Gram negative bacteria have a lower peptidoglycan and higher lipid content. When a dye (eg. crystal violet and subsequently added iodine, which complexes with the crystal violet,) is applied to the bacteria, the cell wall retains the dye. In presence of alcohol, the cell wall of Gram positive bacteria dehydrates and thus causes closing of the pores in the cell wall. This closing of pores results in the retention of the dye. However, alcohol dissolves the higher lipid content in the Gram negative bacterial cell wall causing the dye to leach out into the solvent (alcohol). This action thus causes decolorization of the Gram negative bacteria.

However, if exposure to alcohol is prolonged, the dye leach outs from the cell wall of Gram positive bacteria as well.

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