1.2 Potential bacterial targets for antibiotics
In Activity 2 you will discover which essential cell processes in the bacterial pathogen are potential targets for antibiotics.
Activity 2 When are bacteria vulnerable to antibiotics?
Watch the video about key bacterial cell processes and answer the related questions. You can pause the video to work through this activity at your own pace.
(a) Suggest a likely consequence for the cell if DNA replication is blocked.
Blocking DNA replication would impair cell division and kill the bacterial cell.
(b) Which stage or stages of protein synthesis could be targeted by antibiotics?
Interference with either stage of protein synthesis could result in faulty enzymes and/or structural proteins.
(c) DNA replication, metabolic reactions and protein synthesis also occur in eukaryotic cells. Suggest why antibiotics that target these bacterial processes demonstrate selective toxicity.
Although cellular processes of prokaryotic and eukaryotic cells have many similarities, antibiotics are selected for clinical use that target those processes that are wholly or partly unique to the bacterial pathogen. This minimises the risk of side effects in the patient.
(d) What might happen to a cell that can no longer make a cell wall?
Bacterial cells that lack a cell wall are in danger of bursting if too much water moves into the cell by osmosis
(e) Why do antibiotics that target cell wall synthesis leave eukaryotic cells unharmed?
Eukaryotic cells lack a cell wall.
(f) A relatively small number of antibiotics target the bacterial cell membrane. Such antibiotics are often highly toxic to the host. Can you suggest a reason for this?
The membrane of animal and human cells has a very similar structure to that of bacteria. The potential for such antibiotics to adversely affect eukaryotic cells is therefore greater and these antibiotics generally demonstrate poor selective toxicity. This increases the risk of harmful side effects for the patient.
In Week 1 you learned that structurally similar antibiotics tend to have similar antibacterial activity and are grouped together in the same class. You should by now appreciate that each class of antibiotic has a specific mode of action, affecting susceptible bacterial cells in a way that depends on the drug’s affinity for a specific target or process in the bacterial cell.
You will explore different modes of antibiotic action in Section 2.