Why does penicillin kill only growing bacterial cells and no

Why does penicillin kill only growing bacterial cells, and not eukaryotes or dormant bacteria? Explain how penicillin works.

Solution

Antibiotic is the substance produced by one microorganism and this substance will have the ability to inhibit or destroy the growth of another microorganism.

Most bacteria will be seen producing a cell wall which is composed partly of a macromolecule called peptidoglycan and it is made up of by the assembly of amino sugars and short peptides. Peptidoglycan is only found in bacterial cells but humans cells do not make or need peptidoglycan.

When it comes to penicillin action, it prevents the final cross-linking step, or transpeptidation, taking place during the assembly of peptidoglycan macromolecule.

Due to penicillin interference, the crosslinking will get affected, as a result the cell wall will be very fragile and it will bursts, killing the bacterium. But at the same time it will not cause any harm to the human host because penicillin does not inhibit any biochemical process which is taking place in our body.

That is the main reason why penicillin works on actively growing bacteria. It cannot work on dormant bacteria, as this bacteria will not be synthesizing peptidoglycan, so it cannot interfere with final cross-linking step, but once if this dormant bacteria will start multiplying, penicillin will show its action.