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How does penicillin kill bacteria?

Hey Guys,

As the thread title suggestion i will rep you for an accurate, detailed explantation of how penicillin kills bacteria. In particular, E.coli and bacillus Subtilis. Thanks in advance.

Reply 1

Mwoah

A few pointers:

Competitive inhibition of the enzyme, I think DD-transpeptidase, or something similar that forms cross links between peptidioglycans in bacteria cell walls. Without it they disintegrate.

It's all on the internet I'm sure.

Reply 2

Oracle_163

bcji

Hey Guys,

As the thread title suggestion i will rep you for an accurate, detailed explantation of how penicillin kills bacteria. In particular, E.coli and bacillus Subtilis. Thanks in advance.

Penicillin inhibits the formation of peptidoglycan cross linking in the bacterial cell wall, as Mwoah put it so succintly from wikipedia =) Wikipedia actually has quite a good explanation, namely "The β-lactam moiety (functional group) of penicillin binds to the enzyme (DD-transpeptidase) that links the peptidoglycan molecules in bacteria, which weakens the cell wall of the bacterium (in other words, the antibiotic causes cytolysis or death due to osmotic pressure). In addition, the build-up of peptidoglycan precursors triggers the activation of bacterial cell wall hydrolases and autolysins, which further digest the bacteria's existing peptidoglycan." (wikipedia)

But you don't need to know all this. In other words, for an A-Level standard answer, the mechanism of action is that it inhibits the cross-linking of peptidoglycan (or murein) molecules in the cell wall of the bacteria. Stopping this cross-linkage means that the exterior peptidoglycan wall is now weakened, similarly to when cross links do not form in a B-pleated sheet in proteins. Consequently, the cell wall is weakened enough for osmotic lysis to occur, where the cell wall ruptures due to the high external osmotic pressure (think of the high pressure exerted on a submarine that is at the floor of the sea bed and think of the hull being weakened) and cytosol or other fluid enters the bacteria, causing it to die. This mechanism works for both E.Coli and Subtilis (it is usually the same for all kinds of bacteria).