Question

What is one structural difference between Staphylococcus aureus (Gram-positive bacterium) and Escherichia coli (Gram-negative bacterium) that would make them have different susceptibilities to antimicrobial agents?

Answer 1

The structural difference between the Staphylococcus aureus, a Gram-positive bacteria and E. coli, a Gram-negative bacteria occurs in the structure of their cell walls.

The Gram-positive bacteria like Staphylococcus aureus lack lipopolysaccharide outside the cell wall but has a thick layer of peptidoglycan.

On the other hand, Gram-negative bacteria like E. coli have a layer of lipopolysaccharides.

In gram positive bacteria the antibiotics reach the cell wall and prevent cell wall synthesis or formation. Thus Gram-positive bacteria are more susceptible to antibiotics.

On the other hand, Gram-negative bacteria have a thick lipopolysaccharide layer which prevents the antibiotics from entering inside and these antibiotics depend upon the porin channels to enter inside to act against the bacteria.

Thus Gram-negative bacteria are more resistant to antibiotics than Gram-positive bacteria.

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