Time allowed: 2 hours Answer ALL questions in Section A, ALL PARTS of the question in Section B and ONE question from Section C.

Transcription

1 UNIVERSITY OF EAST ANGLIA School of Biological Sciences Main Series UG Examination MICROBIOLOGY BIO-2B28 Time allowed: 2 hours Answer ALL questions in Section A, ALL PARTS of the question in Section B and ONE question from Section C. Write answers to EACH SECTION in a SEPARATE booklet. The maximum number of marks available for your answers in SECTION A is 40 marks The maximum number of marks available for your answer in SECTION B is 30 marks The maximum number of marks available for your answer in SECTION C is 30 marks The TOTAL number of marks available for the paper is 100 Numbers in square brackets [ ] indicate the relevant mark applied to each part of the question. Graph paper is provided. Notes are not permitted in this examination. Do not turn over until you are told to do so by the Invigilator. BIO-2B28 Module Contact: Prof Andrew Johnston, BIO Copyright of the University of East Anglia Version 1

2 2 SECTION A: MULTIPLE CHOICE AND SHORT ANSWER QUESTIONS. Answer ALL questions. Unless stated otherwise all multiple choice questions have ONE answer. 1. What is unusual about the prion infectious particle? [3 mark] 2. Define the following disease distribution patterns: (a) Sporadic (b) Endemic (c) Epidemic (d) Pandemic 3. Define the terms bioaugmentation and biostimulation. 4. Name three ways by which bacteria can move. [3 marks] 5. Name four ways in which nitrogen-fixing bacteria can protect their nitrogenase from oxygen-mediated damage. 6. Briefly describe what dimorphism is and how fungi can use it to advance disease progression. 7. How can bacteria in the genus Agrobacterium be used as a tool for genetic modification? [3 marks] 8. Who proved that alcoholic fermentation was the result of microbial activity? Section A begins continues/...

3 3 /Section A continued 9. What is the approximate limit of resolution of the electron microscope? Choose ONE answer. a) 0.2 μm b) 2 μm c) 2 nm d) 0.2 nm e) 20nm 10. What is the name of the structure that is made by a bacterial donor cell and which latches onto the recipient during conjugation? 11. List Koch s postulates. 12. What are the partners in the lichen symbiosis? [2 marks] 13. Outline the main stages in a generic viral life cycle. 14. Plant pathogenic bacteria deliver effector proteins into their hosts by which secretion system? Choose ONE answer. a) The TAT secretion system b) Type I c) Type II d) Type III e) Type IV 15. When a bacterium successfully infects a plant host and establishes disease this is known as which of the following? Choose ONE answer. a) An incompatible interaction b) A compatible interaction c) A hypersensitive response d) A hyposensitive response e) A sensitive interaction END OF SECTION A Section B begins on next page/... TURN OVER

4 4 SECTION B: Answer ALL PARTS of this question 16. You are a food microbiologist who has been asked to count the numbers of viable Lactobacillus casei in two commercially available probiotic products, called A and B. (a) You obtained the following colony count data from a dilution series of three independent samples from each product. For sample A, you spread-plated 100 µl of the 10-3 dilution. For B, you spread-plated 100 µl of the 10-5 dilution. (i) Using the information in Table 1, calculate the average numbers of colonyforming units (cfu)/ml of the A and of B products. (ii) Which product appears to have more viable numbers of L. casei? (iii) What test could you undertake in order to see if there was a statistical difference between the two products in terms of the number of viable L. casei bacteria? Colony Numbers per plate Sample 1 Sample Sample 3 2 A Product B Product Table 1. The numbers of viable L. casei bacteria in samples of two probiotic products (b) You then were asked to test how well the L. casei from the two different products survived artificial gastric juice. You tested bacterial viability over time for three independent samples of each product. The average number of colonies for each time period is provided in Table 2. For A, a 100 µl sample was taken from a 10-2 dilution. For B, a 100 µl sample was taken from a 10-4 dilution. (i) Using information in Table 2, calculate the cfu/ml for each time point for each product. (ii) Plot a graph of the data. (iii) Describe the trends you see for each product. [6 marks] [2 marks] Section B continues/

5 5 /Section B continued (iv) Which product in your opinion is better in terms of the numbers of viable L. casei that remain at the end of the survival study? [3 marks] (v) Describe how you might conduct an in vivo study of L. casei survival. [6 marks] Time (mins) Average Number of Colonies for the A Product Average Number of colonies for the B Product Table 2. Average number of colonies for each time period (c) A problem has occurred during the manufacturing process of the A product. A bacterial contaminant has been found. Describe some of the different techniques you could use in order to identify this bacterial contaminant. [3 marks] END OF SECTION B SECTION C: ESSAY QUESTION Answer ONE question [30 marks] 17. Discuss the different mechanisms that various microbial pathogens use in order to infect a human host. 18. Compare and contrast the signal/quorum sensing pathways in Gram negative and Gram positive bacteria. 19. Compare and contrast fungal and bacterial infections of plants. END OF PAPER

6 6 BIO-2B28 EXAMINATION MARKERS [Do not print this when printing to take to Examinations Office! This is for our information only.] Question No. 1 st Marker 2 nd Marker Section A Q1-15 All n/a Section B Q16 Dr K Yeoman Dr H James Section C Q17 Dr H James Dr K Yeoman Section C Q18 Dr G Kelemen Prof AW Johnston Section C Q19 Dr K Yeoman Dr C Thomas