The aim of this experiment was to examine the mechanisms and effects of antibiotic drugs on bacteria, using rifampicin and chloramphenicol as examples. Antibiotics are described as microorganisms that kill or inhibit the growth of other microorganisms, including bacteria such as Escherichia coli (E.coli). Antibiotics can be separated into two classes depending on their mechanism of action: Bacteriostatic – inhibit bacterial growth and prevent bacteria from reproducing, and Bactericidal- microorganisms that kill bacteria. Bacteriostatic antibiotics interfere with the protein production of the bacteria. Chloramphenicol is an example of a bacteriostatic drug. It is a wide spectrum antibiotic which means it can act on many types of bacteria. Chloramphenicol…show more content… In this system rifampicin is acting as a bactericidal antibiotic (killing bacteria) by inhibiting RNA polymerase and therefore RNA synthesis.
Q3. Chloramphenicol is bacteriostatic (stops bacterial growth) by inhibiting protein synthesis. However it has no effect on this system as this system deal with RNA replication. RNA replication is a process which is upstream of protein synthesis. Therefore inhibiting protein synthesis has no effect on this system.
. This system is acting on a protein, therefore chloramphenicol (bacteriostatic) stops the growth of the E.coli by inhibiting protein synthesis.
Q2. If the centrifuged supernatant was replaced and the pellet resuspended with fresh control medium and [3H]-methionine no antibiotic would be present. As a result bacterial growth would be observed.
Q3. B-lactam antibiotics break down peptidoglycan in bacterial cell wall by inhibit the cross linking enzyme transpeptidase. In this system they would decrease the amount of bacteria (the CPM) but the [3H]-methionine would still be present. This is because B-lactam antibiotics don’t interfere with protein…show more content… Rifampicin would have no effect in this system since it acts upstream of protein synthesis (RNA replication). TCA was used again to precipitate out the RNA. The control acted as expected (continued bacterial growth). Chloramphenicol shows its bacteriostatic effect by stopping bacterial growth in this system (CPM values remain the same quickly after chloramphenicol addition). It does so by binding L16 protein of the 50S ribosomal subunit and inhibiting peptidyl transferase. This prevent the tRNA from binding to the mRNA and thus no peptide chains, and as a result no proteins, are