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Date May 2019 Marks available 1 Reference code 19M.3.SL.TZ2.10
Level Standard level Paper Paper 3 Time zone Time zone 2
Command term Suggest Question number 10 Adapted from N/A

Question

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.

Suggest one reason, other than quorum sensing, for the resistance to antibiotics of a biofilm.

[1]
b.

Markscheme

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 ✔

a.

a. polysaccharide matrix/EPS does not let antibiotic pass/limits transport of antibiotic ✔

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 ✔

OWTTE

b.

Examiners report

This question, about biofilm formation in a mammary gland, was poorly answered overall.

a.

This question, about biofilm formation in a mammary gland, was poorly answered overall.

b.

Syllabus sections

Option B: Biotechnology and bioinformatics » Option B: Biotechnology and bioinformatics (Core topics) » B.3 Environmental protection
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Option B: Biotechnology and bioinformatics » Option B: Biotechnology and bioinformatics (Core topics)
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