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Date	November 2016	Marks available	6	Reference code	16N.3.HL.TZ0.13
Level	Higher level	Paper	Paper 3	Time zone	TZ0 / no time zone
Command term	Explain	Question number	13	Adapted from	N/A

Question

Explain the formation of biofilms and the problems associated with their formation.

Markscheme

Formation
a. biofilm is a group of microorganisms embedded in a «exopolysaccharide/EPS» matrix

b. microorganisms adhere on a surface/to each other

c. cells are able to communicate/cooperate via quorum sensing
OR
secrete molecules that facilitate the aggregate adhering to the surface
OR
facilitate individual cells sticking together/OWTTE

d. phenotypic shift in behaviour
OR
emergent properties appear
OR
differential regulation of genes

Problems
e. «formation of biofilms» in the body facilitates infections/OWTTE

Accept any verifiable health problem caused by biofilms, e.g. dental plaque causing caries, lung infection in cystic fibrosis patients, etc.

f. clogging/corrosion of pipes in water systems

g. transfer of microorganisms in ballast water

h. contamination of surfaces in food production

i. highly resistant to antimicrobial agents/antibiotics

j. EPS provides a physical barrier to the entry of the antibiotic «into the colony»

Award [5 max] if only problems are mentioned.

Examiners report

[N/A]

Syllabus sections

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

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