Question

Please compare/ contrast gram+ and gram- cell wall at the structural level, in antibiotic treatment, disease and how the bacterium survives in the environment in different conditions.

type completely explain, thanks.

Answer 1

Bacteria are classified into two types based on the Gram staining method to Gram-positive and Gram-negative, developed by Hans Christian Gram which identifies bacteria based upon the reaction of their cell walls to certain dyes and chemicals.

Gram-positive and Gram-negative bacteria differ in their cell wall composition. Gram-positive stain purple colour with gram stain due to thick peptidoglycan, or murein layer as the cell wall. Gram-negative bacteria stain red or pink due their cell walls have a thin layer of peptidoglycan with an outer membrane of lipopolysaccharide which will not present in Gram-positive bacteria.

Gram-Positive Bacteria vs Gram-Negative bacteria

The gram-positive bacterial cell wall is made several layers of peptidoglycan which is a mixture of sugars (N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) and amino acids. Another component of the cell wall is teichoic acid that extends from the plasma membrane to cell wall and helps bacteria to infect the cell and cause disease and in the division of bacteria.

Whereas Gram-positive bacterial cell wall is composed of a single thin layer of peptidoglycan. The complex cell wall is located between the plasma membrane like a gel-like matrix called periplasmic space. Membrane proteins, murein lipoproteins, attach the outer membrane to the cell wall. The unique characteristic of Gram-negative bacteria is the presence of lipopolysaccharide (LPS) molecules on the outer membrane.

LPS is a large glycolipid complex that protects bacteria from harmful substances in their environment. It is also a bacterial toxin (endotoxin) that can cause inflammation and septic shock in host body if it enters the blood. Three components of the LPS are Lipid A helps in attaching the LPS to the outer membrane, core polysaccharide, and an O antigen attached to the core polysaccharide used to identify specific strains of harmful bacteria.

There are some bacteria which forms spores when they encounter the harsh environment like low or high oxygen levels, high or low temperatures. In recent days bacteria have become antibiotic tolerant either degrading with enzymes or not to allow them to enter into the body.