Why are gram + cells more susceptible to penicillin and gram - cells less sensitive to penicillin?

Answer 1

Gram positive bacteria have a substance in their cell walls called peptidoglycan. Gram negative bacteria have a less-complex cell wall with much less peptidoglycan. Antibiotics such as penicillin interfere with the sysnthesis of peptidiglycan and prevent the formation of a cell wall.

Answer 2

The answer above does not convince me.

I am a microbiologist, in a clinical lab. We use penicillins against Gram Negative bacteria. Ampicillin is in the panel of antibacterials that we routinely test against E. coli, for example.

I suppose that penicillin G might not work, but IMO the difference cannot simply be that Gram Negative bacteria need their cell wall less that Gram Positive bacteria do. If you digest it with lysozyme, they will round up, just like Gram Positive bacteria do, and will swell and lyse, in hypotonic solutions.

Maybe penicillin G has trouble getting through their outer membrane, due to some chemical interaction or steric hindrance, while Ampicillin can get in?

Answer 3

Because of the membrane structure & the reeptors present on this memberane.
each drug has specific active sites, these binds with receptors & then the activity of the drug is collected.

Gram - has different memberanous structure then gram +