Division of Science and Technology
School of Science
SS12BMI Microbiology
Final Examination

November, 1994

  1. (I) What is the purpose of staining when examining cells using a light microscope?

    (ii) Briefly describe ways in which nutrients may pass through the cytoplasmic membrane and into the cell.

    (iii) What are the functions of the following cell structures:

    a. cell wall
    b. cytoplasmic membrane
    c. ribosomes
    d. mitochondria
    e. endospores

    (iv) Discuss the influence of temperature on the growth of cells.

    (v) Describe the influence of three factors (other than heat) which will affect microbial growth.

  2. (I) Describe the taxonomy of photosynthetic procaryotes.

    (ii) Describe lithotrophy, and the variety of lithotrophic procaryotes.

    (iii) Describe the significance of morphology, and modes of motility in the taxonomy of bacteria.

    (iv) Answer one (1) only of the following:

    a. Describe the taxonomic test used to differentiate the following genera: Vibrio; Escherichia; and Pseudomonas, and name one disease caused by a member of each;

    b. Describe the Enterobacteriaceae and list six of its genera;

    c. Compare Mycoplasmas, Rickettsias, and Chlamydias, and name one disease caused by a member of each group.

    (v) Answer one (1) only of the following:

    a. Discuss the diversity of the low Mole% GC Gram-positive bacteria, listing members of environmental, industrial, and medical importance.

    b. Discuss the diversity of the high Mole% GC Gram-positive bacteria, listing members of environmental, industrial, and medical importance.

    (vi) Answer one (1) only of the following:

    (i) Describe the extremely halophilic Archaebacteria;

    (ii) Describe the extremely thermophilic Archaebacteria;

    (iii) Describe the methanogenic Archaebacteria.

  3. Answer seven (7) questions only.
    Write short answers i.e. 4-5 lines.
    Use diagrams to illustrate your answers and give examples wherever possible.
    DO NOT write in pencil.

    (i) Write short notes on "The Nature of Viruses".

    (ii) Write short notes on viral composition.

    (iii) Discuss groups of viruses infecting plants.

    (iv) Explain the difference between "helical" and "icosahedral" structures.

    (v) Explain the structure of T phages.

    (vi) Discuss "lysis" and "lysogeny" in phages.

    (vii) Viruses are obligate parasites. Discuss.

    (viii) Discuss "one-step growth curve" of virus replication.

    (ix) Write short notes on MS2 OR Write short notes on Øx174

    (x) Discuss the replication cycle of ± DNA phages.

    (xi)Write short notes on the transmission of plant viruses.

    (xii)What are `inclusion bodies' and how are they formed?

  4. Answer two of the following:

    (i) A patient complaining of symptoms characteristic of a STD (Sexual Transmitted Disease) has blood, a urethral swab and urine collected for examination. indicate microbiological procedures that would be used to provide a definitive diagnosis. Indicate infectious agents likely to be diagnosed by each microbiological procedure.

    (ii) "The presence of normal bacterial flora benefits the host but it also may be the source of infectious agents."

    Briefly explain the benefits to the host of the bacterial normal flora and how normal flora may be the source of infections.

    (iii) Virulence factors are factors that help bacteria to (1) invade the host, (2) cause disease, and (3) evade host defences. Indicate a specific type of virulence factor that represents each of these mechanisms of bacterial pathogenesis. Briefly describe the role of each of these virulence factors and the likely genetic source.

  5. Biochemistry of Microbes

    Question 1 is compulsory (11 marks)

    Choose THREE ONLY from questions 2, 3, 4, 5, 6 (8 marks each, making a total of 24 marks)

    Total marks for this section: 11 + 24 = 35 marks

    You must do the following question

    1. Pyruvic acid (i.e. pyruvate) is the most important intermediate compound of microbial metabolism.

      Use diagrams to show the pivotal role of pyruvate in microbial metabolism. ( Note: structures, apart from that of pyruvate, need not be shown.).

      Choose THREE only questions from questions 2, 3, 4, 5, or 6.

    2. Describe the biochemical adaptations that allow EITHER

      (i) halophilic organisms
      (ii) thermophilic organisms to thrive in extreme conditions

    3. Geologists estimate that the atmosphere of the primitive earth was essentially devoid of oxygen until cyanobacteria first evolved. Show diagrammatically how cyanobacteria are able to produce oxygen by the process of photosphorylation.

    4. Metabolic products from microorganisms can have either beneficial or detrimental effects. give two examples of beneficial organisms and two examples of detrimental organisms, explaining how these effects come about as a result of their metabolism.

    5. Ruminants and termites both contribute to atmospheric pollution. Explain.

    6. The following table shows the free energy change associated with electron transport phosphorylation using hydrogen as the redcurrant.

      Redox coupleG (kJ per mole hydrogen)

      Show the reaction and estimate the free energy changes associated with electron transport phosphorylation for the following reactions:

      (I) Reduction of corbon dioxide to methane, in methanogenic archaea

      Reaction is:

      Go, =

      (ii) Reduction of sulphate to sulphide in sulphate-reducing bacteria (SRB)

      Reaction is:

      Go, =

      (iii) Reduction of nitrate to nitrite

      Reaction is:

      Go, =

      (iv) Reduction of oxygen to water in aerobic bacteria

      Reaction is:

      Go, =

      Based on the free energy changes, would you expect anaerobes to grow more or less slowly than aerobes? Explain.

Author: Dr Bharat Patel <>
HTML'd by Troy Baalham
[Created: 01 Apr 1996]
[Modified: 20 May 1996]