| Date | November 2017 | Marks available | 1 | Reference code | 17N.3.HL.TZ0.11 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | State | 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.
State a positive application of biofilms.
Suggest two problems that could be caused by the presence of biofilms in water systems.
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. 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]
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]
