Why are certain gram-negative bacteria more resistant than gram-positive bacteria to antibiotics that attack cytoplasmic targets?
In Gram-negative bacteria the cell wall is surrounded by an extra layer made of polysaccharides, proteins, and phospholipids. This layer, though easily washed away by alcohol-acetone mixtures, blocks many antibiotics from reaching the peptidoglycan cell wall. Since b-lactam antibiotics like penicillin work by attacking the cell wall, this outer layer makes Gram-negative bacteria resistant to such antibiotics.
