Question 19M.3.HL.TZ2.10
| Date | May 2019 | Marks available | [Maximum mark: 5] | Reference code | 19M.3.HL.TZ2.10 |
| Level | HL | Paper | 3 | Time zone | TZ2 |
| Command term | Outline, Suggest | Question number | 10 | Adapted from | N/A |
The diagram shows the formation of a biofilm in a mammary gland, producing a mastitis infection.
[Source: © International Baccalaureate Organization 2019]
Outline the process of quorum sensing in bacteria forming a biofilm.
[2]
a. cells/bacteria in a biofilm are close together ✔
b. cells secrete signaling molecules ✔
c. «signaling molecules» bind to receptors of other cells
OR
«signaling molecules» allow communication between cells ✔
d. a threshold is reached which enables emergent properties ✔
Most candidates seem to have a very good knowledge of biofilms, but it was more difficult to outline quorum sensing properly and suggest a reason for antibiotic resistance.
Suggest one reason, other than quorum sensing, for the resistance to antibiotics of a biofilm.
[1]
a. polysaccharide matrix/EPS does not let antibiotic pass/limits transport of antibiotic ✔ OWTTE
b. reduced metabolic activity/growth rate of bacteria in biofilm contributes to resistance ✔
c. increased cell density limits transport of antibiotic «to the interior of biofilm» ✔
d. «horizontal» transfer of antibiotic resistance via plasmids ✔
Most candidates seem to have a very good knowledge of biofilms, but it was more difficult to outline quorum sensing properly and suggest a reason for antibiotic resistance.
Outline one example of an environmental problem caused by biofilms.
[2]
a. area where biofilm problem exists ✔ eg emptying introduces invasive bacterial species into coastal waters.
b. environmental concern ✔
Allow other verified examples
Most could outline an example of biofilms but they had more difficulty relating it with an environmental concern.