Why are certain gram-negative bacteria more resistant than gram-positive bacteria to antibiotics that attack cytoplasmic targets?
by 
salley
ANSWERS: 4
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It has to do with the cell wall thickness.
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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.
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as the wall of gram negative bacteria contain extra layer outside the peptidoglycan layer composed of phospholipid ,lipopolysaccaride (LPS) (lipid A ,core polysaccarides & O-antigen ) and murein lipoprotein . this layer give cell wall of bacteria its negative charge , so possitive cations like Mg &Ca caions are attracted to the cell wall &chelated between adjacent LPS molecules causing stabilization of the outer membrane . If we add subastance that complex with Mg cation .eg, (EDTA) ,it will make dispertion of LPS & any small amount of antibiotic will kill the bacteria .
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This is not so true the gram positive bacteria have thiker mureane layer with nicotic acid so gram positive bacteria have more resestane than gram negative ones (LPS) is qute thin layer but some bacteria As E-coli can make spetial anibiotic reseitance see the pic
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