Describe the way in which penicillin kills non-resistant bacteria.
A bacterium can be resistant to an antibiotic such as a $\beta$ lactam because it has protein pumps in its cell surface membrane that remove the antibiotic from the bacterium. The gene that codes for this efflux pump is found on a plasmid. Outline how the bacterium makes an efflux pump from a gene on a plasmid.
The bacterium $Pseudomonas\ aeruginosa$, strain R, has a gene for an efflux pump and is resistant to a $\beta$ lactam antibiotic. The minimum inhibitory concentration (MIC) of the $\beta$ lactam for strain R was measured. The MIC is the lowest concentration of antibiotic that stops a colony of the bacterium from growing. MICs were also measured for two mutant strains taken from strain R, mutant strain 1 and mutant strain 2. Each of these strains differs from strain R in how the gene coding for the efflux pump is expressed. The MICs for the three strains of $P.\ aeruginosa$ are shown in Table 2.1. Using Table 2.1, suggest why the MICs for mutant strains 1 and 2 are different from that for strain R.
Suggest how a population of strain R of $P.\ aeruginosa$ could be replaced by mutant strain 2.
In what way could a population of strain R of $P.$ $aeruginosa$ be replaced by mutant S?