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Date November 2017 Marks available 3 Reference code 17N.3.HL.TZ0.11
Level Higher level Paper Paper 3 Time zone TZ0 / no time zone
Command term Outline Question number 11 Adapted from N/A

Question

The scanning electron micrograph shows a biofilm on a metal surface from an industrial water system.

[Source: Biofilms: Survival Mechanisms of Clinically Relevant Microorganisms, Rodney M. Donlan, J. William Costerton, Clinical Microbiology Reviews, 2002, 15 (2), pp. 167–193. Reproduced with permission from American Society for Microbiology]

Outline the emergent properties of biofilms.

[3]
a.

State a positive application of biofilms.

[1]
b.

Suggest two problems that could be caused by the presence of biofilms in water systems.

[2]
c.

Markscheme

a. properties not present in individuals but present/develop only in the aggregate

    OWTTE

b. develop structure/architecture/scaffolding

    OR

    develop an «extracellular» matrix/EPS

c. signaling/communication

d. migration/movement

e. resistant to antimicrobial agents

f. cooperates through quorum sensing

[Max 3 Marks]

a.

a. sewage/waste water treatment/trickle filter beds

b. «bio»remediation of contaminated soil/water

c. metal extraction from ore deposits/microbial leaching

Accept other valid positive application

eg: decay/breakdown contaminants, such as petroleum

[Max 1 Mark]

b.

a. contamination/pollution «of water system»

    OR

    «microbial growth of biofilm» causes disease through water systems

b. difficult to eliminate «from water systems»

c. fouling/clogging of water pipes

d. corrosion of water pipes

OWTTE

[Max 2 Marks]

c.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.

Syllabus sections

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