UNIVERSITY OF YORK BA, BSc, and MSc Degree Examinations

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1 Examination Candidate Number: Desk Number: UNIVERSITY OF YORK BA, BSc, and MSc Degree Examinations Department : BIOLOGY Title of Exam: Bacterial pathogenesis Time Allowed: 2 hours Marking Scheme: Total marks available for this paper: 100 Sec on A: Short Answer / Problem / Experimental Design ques ons (50 marks) Sec on B: Essay ques on (marked out of 100, weighted 50 marks) The marks available for each ques on are indicated on the paper Instructions: Sec on A: Answer all ques ons in the spaces provided on the examina on paper Sec on B: Answer either ques on A or ques on B. Write your answer on the separate paper provided and a ach it to the back of the ques on paper using the treasury tag provided. For marker use only: For office use only: Module total as % DO NOT WRITE ON THIS BOOKLET BEFORE THE EXAM BEGINS DO NOT TURN OVER THIS PAGE UNTIL INSTRUCTED TO DO SO BY AN INVIGILATOR page 1 of 9

2 SECTION A: Short Answer / Problem / Experimental Design questions Answer all questions in the spaces provided Mark total for this section: You wish to determine a competitive index (CI) experiment to assess the role of a specific gene in causing bacterial diarrhea. The bacterial species is poorly characterized but the gene s sequence resembles an enterotoxin in a different pathogenic species. Your supervisor asks you to address the 3Rs first and also to convince him of the value of your proposed CI experiment. Explain the supervisor s request and outline how you would address both points. (10 marks) page 2 of 9

3 2. Briefly discuss the benefits and challenges of phase variation of an adhesin for a bacterial pathogen. the space above this line should be sufficient for your answer page 3 of 9

4 3. In what ways is anaerobic respiration important for the success of E. coli in colonising host tissue? (10 marks) page 4 of 9

5 4. a) What determines the size of a bacterial pathogen genome? b) You suspect a particular gene from an enteric pathogen is important in gut colonisation. Describe how you could identify the function of the gene, and determine whether it is important for colonisation of a mammalian host. page 5 of 9

5. The electron micrograph (below) shows part of a eukaryotic cell infected with a mutant bacterium that has a gene of unknown function ( unfun1 ) deleted.

6 5. The electron micrograph (below) shows part of a eukaryotic cell infected with a mutant bacterium that has a gene of unknown function ( unfun1 ) deleted. a) Suggest what membranes (indicated by arrows) could be surrounding the bacterium? (2 marks) b) The membrane surrounding the bacterium was subsequently shown to contain the lipidated protein LC3/ATG8. What process is likely to clear the bacterium from the cell? (2 marks) c) In wild type bacteria containing unfun 1, intracellular bacteria are not seen associated with eukaryotic membranes. What can you conclude about the function of UNFUN1? (1 mark) page 6 of 9

7 d) The predicted structure of UNFUN1 is shown (above), where the numbers refer to the positioning of amino acids. You perform a GST pulldown experiment with GST fused to different parts of UNFUN1. You subsequently undertake a western blot (above) for binding of LC3 to the GST-fusion proteins. Explaining your answer, where does LC3 bind to UNFUN1? page 7 of 9

8 6. A signature tagged mutagenesis experiment is undertaken, which identifies a gene that is essential for bacterial intracellular survival. Describe two experiments and/or analyses that you could perform to determine the function of the protein. the space above this line should be sufficient for your answer page 8 of 9

9 SECTION B: Essay question Answer one question on the separate paper provided Remember to write your candidate number at the top of the page and indicate whether you have answered question A or B Mark total for this section: 50 EITHER A) Discuss strategies employed by bacterial pathogens to optimise their success in colonising host tissues. OR B) What makes the perfect intracellular bacterial pathogen? page 9 of 9

BA, BSc, and MSc Degree Examinations

Examination Candidate Number: Desk Number: BA, BSc, and MSc Degree Examinations 2017-8 Department : BIOLOGY Title of Exam: Bacterial pathogenesis Time Allowed: 2 hours Marking Scheme: Total marks available