| Date | May 2019 | Marks available | 1 | Reference code | 19M.3.HL.TZ1.11 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Suggest | Question number | 11 | Adapted from | N/A |
Question
Some halophilic bacteria biodegrade benzene, which makes them useful in treating oil spills as benzene is contained in crude oil. Investigators added cultures of the bacteria to benzene solutions at different salinities in containers. The amount of benzene remaining in the container was recorded once a week for two weeks.
[Source: adapted from C A Nicholson and B Z Fathepure, (2004),
Applied and Environmental Microbiology, 70 (2), pages 1222–1225]
Outline what is meant by halophilic when describing the bacteria.
Identify the salt concentration with the greatest rate of benzene biodegradation.
………………......… mol m–3
State one genus of halophilic bacteria known to biodegrade benzene.
Suggest one advantage to the bacteria of breaking down benzene.
Markscheme
thrive/live in a salt rich environment ✔
1 mol m–3 ✔
Marinobacter ✔
Allow other correct responses eg: Dechloromonas, Haloferax, Pseudomonas, Fusarium, Halomonas, Halococcus,
Halobacterium, Haloarcula, Haloarchaea, Fundibacter, Fusarium, Alcanivorax, Dietzia
a. energy gained from the benzene ✔
b. benzene acts as a source of carbon ✔
Examiners report
(a) to (c) These three questions were often answered well.
(a) to (c) These three questions were often answered well.
(a) to (c) These three questions were often answered well.
Very few students could state that the breakdown of benzene could be used as a source of carbon or energy.
Syllabus sections
- 18M.3.SL.TZ2.8c: Outline the concept of an emergent property.
- 17M.3.SL.TZ1.16a: Calculate the diversity of site C. Working should be shown.
- 18M.3.SL.TZ2.9b: State the name of the strategy that involves the use of organisms to remove toxic substances...
- 17M.3.SL.TZ1.11a: Determine the optimum concentration of sodium chloride for benzene degradation.
- 17M.3.SL.TZ1.10a: Evaluate the effect of 1 % ginger root extract on biofilm formation.
- 17N.3.SL.TZ0.10a: State the effect chlorination has on the accumulation of biofilm in the pipe.
- 17N.3.SL.TZ0.10c: Identify which two pipes would be required to study the effect of heat on biofilm accumulation.
-
16N.3.SL.TZ0.10b:
Explain two ways in which bacteria of the genus Pseudomonas can be used for bioremediation.
-
19M.3.HL.TZ1.11a:
Outline what is meant by halophilic when describing the bacteria.
- 19M.3.HL.TZ2.10b: Outline one example of an environmental problem caused by biofilms.
- 16N.3.SL.TZ0.10a: Outline the emergent properties of biofilms.
- 17M.3.SL.TZ1.10b: Outline the importance of avoiding biofilm formation in pipes carrying drinking water.
- 18M.3.SL.TZ1.10a: State the role of microorganisms in bioremediation.
- 18M.3.SL.TZ2.9a: Outline the trend in amount of salt in the soil over the study period.
-
17N.3.SL.TZ0.10b:
Suggest why membrane filtration may be more suitable than chlorination in purifying the water.
-
17N.3.SL.TZ0.10d:
Explain how quorum sensing benefits the bacteria within the steel pipes.
- 19N.3.SL.TZ0.11b: State one other way in which the formation of biofilms can be inhibited.
- 17M.3.HL.TZ1.10a.ii: Discuss the emergent properties of biofilms.
- 17M.3.HL.TZ2.10a: Outline the evidence that P. fluorescens can degrade the cyanide.
- 17M.3.HL.TZ2.10b: Suggest how the addition of sucrose promotes the degradation of cyanide.
-
19M.3.HL.TZ1.11b:
Identify the salt concentration with the greatest rate of benzene biodegradation.
………………......… mol m–3
- 18M.3.HL.TZ2.10b: Explain the persistence of urinary tract infections, if bacterial biofilms are formed.
-
17N.3.HL.TZ0.11c:
Suggest two problems that could be caused by the presence of biofilms in water systems.
-
17N.3.HL.TZ0.11b:
State a positive application of biofilms.
- 20N.3.HL.TZ0.12a: Bacteria sometimes form biofilms inside metal pipes in water systems. Distinguish between...
- 19M.3.HL.TZ1.9c.i: B. subtilis colonies form biofilms through quorum sensing. Define quorum sensing.
- 19M.3.SL.TZ1.8d: P. aeruginosa is a concern in hospitals because it tends to form biofilms. Outline one reason...
- 19M.3.HL.TZ2.10a.ii: Suggest one reason, other than quorum sensing, for the resistance to antibiotics of a biofilm.
- 19N.3.SL.TZ0.11c: Some biological systems show emergent properties. Emergent properties arise from the...
-
17N.3.SL.TZ0.11:
The picture shows workers cleaning up a polluted stretch of coastline in Alaska after oil was leaked from a tanker.
[Source: https://commons.wikimedia.org/wiki/File:OilCleanupAfterValdezSpill.jpg]
Explain how oil pollution can be treated by bioremediation.
- 18N.3.HL.TZ0.9b: The formation of hydrophobic concrete is an example of how biofilms can be useful. Outline...
- 18N.3.SL.TZ0.11: The micrograph shows a T4 bacteriophage. Discuss the use of bacteriophages in water systems.
- 18N.3.HL.TZ0.9a: Outline the characteristics which would indicate biofilm formation in Bacillus subtilis.
- 19M.3.HL.TZ1.9c.ii: B. subtilis colonies form biofilms through quorum sensing. State three possible advantages to...
- 18M.3.HL.TZ1.11a.i: Define biofilm.
- 17M.2.HL.TZ1.1f.ii: Suggest a reason for the greater expression of the gene for the urea transporter after an...
-
17N.3.HL.TZ0.11a:
Outline the emergent properties of biofilms.
-
16N.3.HL.TZ0.13:
Explain the formation of biofilms and the problems associated with their formation.
-
20N.3.SL.TZ0.11:
Trickle filter beds are used to treat sewage.
[Source: © International Baccalaureate Organization 2020.]
Explain the role of biofilms in sewage treatment.
-
20N.3.HL.TZ0.12c:
State how viruses could be used to treat water systems, in order to avoid the use of a disinfectant.
-
20N.3.HL.TZ0.12b:
The use of monochloramine is replacing the use of chlorine, as it is more stable, but it can produce by-products that pose possible health risks. Evaluate the data to see whether monochloramine is a good choice as a disinfectant for water systems.
- 18M.3.HL.TZ2.10a: Identify the step where the extracellular matrix first appears.
- 17M.3.SL.TZ2.9: The diagram shows a biofilm that has formed on a tooth. Using the diagram, explain the...
- 19M.3.SL.TZ2.10a: Outline the process of quorum sensing in bacteria forming a biofilm.
- 17M.3.HL.TZ1.10a: Biofilms can be formed in many different environments. State one example of an environment...
-
18M.3.SL.TZ1.11:
Explain the difficulties of treating microorganisms growing in biofilms.
-
18M.3.HL.TZ1.11b:
Explain the use of a named bacterium in bioremediation.
- 19M.3.SL.TZ2.10b: Suggest one reason, other than quorum sensing, for the resistance to antibiotics of a biofilm.
- 19M.3.HL.TZ2.10a.i: Outline the process of quorum sensing in bacteria forming a biofilm.
- 17M.3.SL.TZ2.13: Explain how microorganisms can be used in response to pollution incidents such as an oil spill.
- 17M.3.HL.TZ2.10c: With respect to the degradation of cyanide by P. fluorescens, explain what is meant by...
- 19N.3.SL.TZ0.11a: Compare and contrast the effect of ultrafiltration and nanofiltration on the drop in pressure.
-
19M.3.HL.TZ1.11c:
State one genus of halophilic bacteria known to biodegrade benzene.
- 18M.3.HL.TZ2.13: Discuss the use of microorganisms in bioremediation.
-
18M.3.HL.TZ1.11a.ii:
Explain the difficulties of treating microorganisms growing in biofilms.
-
19N.3.HL.TZ0.11a:
Outline the aims and methods of bioremediation.
-
18M.3.SL.TZ1.10b:
Explain the use of a named bacterium in bioremediation.
-
19M.3.SL.TZ2.11:
Explain the use of two named bacteria in response to pollution incidents.
- 17M.3.SL.TZ1.11b: State the genus of halophilic bacteria in the soil that could be degrading the benzene.
![https://commons.wikimedia.org/wiki/File:OilCleanupAfterValdezSpill.jpg]](https://commons.wikimedia.org/wiki/File:OilCleanupAfterValdezSpill.jpg%5D){kind=link}