November 1993


Question 1

Answer any two (2) of the following three (3) questions.

(a) This question is composed of four (4) parts, all of which are to be answered.

(i) Why are 16S rRNAs thought to be the best molecules for undertaking phylogenetic studies?

(ii) What major evolutionary findings emerged from the study of 16S rRNA sequences?

(iii) Describe and discuss the structure of 16S rRNA with respect to its functions in a bacterial cell.

(iv) What are signature sequences and of what phylogenetic value are they?

(b) Discuss the statement citing examples "Complex interactions occur amongst individual microbial cells and microbial populations in an ecosystem".

(c) Discuss the "symbiotic" nature of microorganisms and the prospects and constraints of establishing genetically engineered microbes in the rumen of ruminants.

(60 marks)

Question 2

Write notes on any five (5) of the following. Draw schematic diagrams wherever necessary.

(a) Sampling procedures in microbiology

(b) r and k strategists

(c) Microbiology of the gastrointestinal tract

(d) Skin microflora

(e) Hydrothermal vent communities

(f) Archaea

(40 marks)

Question 3

Answer both questions a and b

(a) Write only the correct alphabet letter against the question number in your answer book

  1. Lignin is broken down in the soil primarily by ______
    a. aerobic fungi
    b. anaerobic bacteria
    c. protozoa
    d. algae

  2. The type of antagonism in which one species is suppressed by the products of another is called ______
    a. amensalism
    b. neutralism
    c. commensalism
    d. parasitism

  3. Most of the methane in air is produced by ______
    a. photosynthetic processes
    b. aerobic oxidation of glucose
    c. reduction of carbonate
    d. anaerobic microbial processes

  4. Which of the following substances is most resistant to microbial degradation?
    a. ligin
    b. cellulose
    c. hemi-cellulose
    d. pectin

  5. The microorganisms normally associated wtih a particular tissue can be
    referred as ______
    a. indigenous microbial population
    b. microbiota
    c. microflora
    d. all of the above

  6. The surface layer of soils usually have ______ microbial numbers to that of lower layers.
    a. High
    b. Low
    c. The same

  7. The microbes in the air are ______ populations.
    a. transient
    b. resident
    c. microbiota
    d. zoonotic

  8. The most numerous bacterium associated with the skin gland is ______
    a. Staphylococcus epideremis
    b. Pityrosporum orale
    c. Propionibacterium acne
    d. Pityrosporum orbiculare

  9. ______is involved in periodontal diseases
    a. Streptococcus mutans
    b. Bacteroides gingivatis
    c. Escherichia coli
    d. Lactobacillus

  10. ______in the gastrointestinal tract is regarded as a barrier to the entry of pathogens.
    a. stomach
    b. jejunum
    c. duodenum
    d. colon

(10 marks)

(b) Answer the following questions in brief.

(i) What type of ribosomal RNA is found in the 30S ribosome subunit of a bacterial cell?

(ii) What is the general secondary structure of ribosomal RNA?

(iii) Name the organ of Riftia pachyptilla in which as yet uncultured symbiotic bacteria are found.

(iv) Do Gram +ve or Gram -ve bacteria predominate in soil?

(v) Give the most important characteristics of marine microorganisms.

(vi) State an approach which you would use to trace genetically modified microorganisms that had been released in an aquatic ecosystem.

(vii) How does S mutans attach to the crevices of the teeth?

(viii) Name three (3) antibacterial agents presnt in the skin.

(ix) ATP levels are similar in all cells. State true or false, qualifying your answer.

(x) What is a biofilm? Cite an example.

(10 marks)


This section is to be answered in a new supplementary answer book.

Question 4A

For each of the statements below, one, or more, or none of the completions given is correct. Choose the appropriate answer as
A if 1, 2 and 3 are correct
B if 1 and 3 are correct
C if 2 and 4 are correct
D if only 4 is correct
E if all are correct
F if none are correct
G if 1 and 4 are correct.

Place the letter (i.e. A, B, C, D, E, F or G) indicating your answer in the answer book.

1. The Entner-Doudoroff pathway in halophilic and thermoacidophilic archaebacteria

  1. Generates pyruvate and glyceraldehyde 3 phospate
  2. Converts glucose 6 phosphate into ribulose 5 phosphate
  3. Produces NADH
  4. Oxidizes glucose into gluconate

2. The modified Entner-Doudoroff pathway in halophiles

  1. Generates NADPH
  2. Consumes ATP
  3. Produces 2 keto 3 deoxygluconate
  4. Generates ATP

3. The citric acid cycle in archaebacteria

  1. Oxidizes acetyl CoA derived from fatty acid degradation
  2. Produces most of the CO2
  3. Provides precursors for biosynthesis of amino acids
  4. Provides succinyl CoA for the synthesis of carbohydrates

4. Which of the following compounds are products of the pentose phosphate pathway in thermoacidophilic archaebacteria?

  1. NADPH
  2. Ribulose 5 phosphate
  3. Glyceraldehyde 3 phosphate
  4. Seudoheptulose 7 phosphate

(20 marks)

Question 4B

Give two features of gene expression (transcription and translation) in the Archaea which are similar to the equivalent features in Bacteria, and two which are similar to the equivalent features in Eukarya.
Write a couple of sentences on each.

(20 marks)

Author: Dr Bharat Patel <>
HTML'd by Troy Baalham
[Created: 08 Jan 1996]
[Modified: 17 Jan 1996]