Universiteit van Pretoria University of Pretoria. Mikrobiologie 251 Toets Maart 2012 Microbiology 251 Test March Examiners: Dr L Moleleki

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1 Universiteit van Pretoria University of Pretoria Mikrobiologie 251 Toets Maart 2012 Microbiology 251 Test March 2012 Tyd: 1 uur Time: 1 hour Eksaminatore: Dr L Moleleki Examiners: Dr L Moleleki Beantwoord alle vrae Totaal :50 Answer all questions Total : 50 Vraag 1 / Question 1: [6] Compare and contrast type I and type II methanotrophs. The type I methanotroph membranes contain bundles of disc-shaped vesicles throughout the cell, and the type II methanotrophs have paired membranes along only the periphery of the cell. The type I methanotrophs assimilate carbon with the ribulose monophosphate cycle, and type II methanotrophs use the serine pathway. Phylogenetically the type I are Gammaproteobacteria and the type II are Alphaproteobacteria Vraag 2 / Question 2 [2] Although the nitrogen-fixing bacterium Azotobacter is an obligate aerobe, the enzyme nitrogenase is oxygen-sensitive. Explain how this enzyme functions in an aerobic atmosphere. Azotobacter can grow in the presence of oxygen with oxygen-sensitive enzymes such as nitrogenase by protecting the enzymes in the cytoplasm. Extensive capsules or slime layers outside of the cell to prevent nitrogenase from contacting oxygen. Vraag 3 / Question 3 [8] Name the two group of enteric bacteria and explain how they can be differentiated based on type and proportion of glucose fermentation patterns. Enteric bacteria are classified into two groups based on the two main patterns of products formed are called the 2,3-butanediol fermenters and the mixed acid fermenters. 2,3-butanediol fermenters:

2 1. the primary products is 2,3-butanediol fermentation (or Butanediol) 2. More CO2 than H2 are produced, 3. small quantities of acids are also formed. 4. Example E.coli Mixed acid fermentaters 1. No butanediol 2. only small quantities of ethanol, CO2 and H (CO2 and H2 are produced are produced in equal amounts) 3. considerably more of the acids acetic, lactic, and succinic acids. 4. Example Enterobacter Vraag 4 / Question 4 [3] Explain the process of quorum sensing as it relates to regulation of bacterial bioluminescence in Vibrio fischeri. - Density dependant It is mediated by autoinducer molecule, acyl-homoserine lactone (AHL), accumulates until a high enough concentration is reached through an increase in cell density making more AHL. - Requires lux operon and is catalised by the enzyme luciferase Vraag 5 / Question 5 [2] Explain the role of the Ti plasmid in causing crown gall disease in plants. - Part of the Ti plasmid is integrated into the plant's genome, called T-DNA. - The T-DNA contains genes that encode for enzymes responsible in tumorigenesis. Opines are also made from the T-DNA and serve as carbon and nitrogen sources for Agrobacterium tumefaciens cells. Vraag 6 / Question 6 [4] State four reasons why small subunit RNAs are most widely used molecular clocks. Found in all domains of life 16S rrna in prokaryotes and 18S rrna in eukaryotes Functionally constant Sufficiently conserved (change slowly) Sufficient length Vraag 7 / Question 7 [5] Discuss process in the rhizophere leading to the symbiotic processes between Rhizobium tropici and bean plants 1. Recognition by the two partners plant and rhizobia (1)

3 2. Secretion of oligosaccharides singalling molecules or nod factors causing root hair curling (1) 3. Bacterial invasion of root hair through infection thread (½) 4. Movement of bacteria to the root using infection thread into the root cell (½) 5. Formation of bacteriod state within the plant (1) 6. Plant and bacteria cell division leading to nodule formation (1) Vraag 8 / Question 8 [10] Match the following bacteria (column I) with a corresponding key characteristic feature in column II. 1I 2E 3H 4G 5B 6J 7D 8C 9A 10F (Column I) Bacteria (Column II) Key characteristic feature 1. Thiothrix A. Butanediol fermenters 2. Neisseria gonorrhea B. Produce a yellow green fluorescent pigment 3. Chromobacterium C. Form symbiotic relationship with certain marines fish spp 4. Vibrio cholarae D. Contain bacteriophylls and carotenoid pigment 5. Pseudomonas E. Gram negative diplococci aeruginosa 6. Serraria marcescens F. Involved in vitamin K synthesis 7. Purple phototrophic bacteria G. Bioluminesce in light organs of marine fish and squids 8. Methanotrophs H. Produce purple pigment (violacein) 9. Enterobacter aerogenes I. Form filaments held together in arrangements known as rosettes 10. Escherichia coli J. Produce a red orange pigment (prodigiosin) Vraag 9 / Question 9 [10]

4 1) The most widely used molecule in sequence-based evolutionary analyses are genes. A) ATPase B) electron transport C) SSU rrna D) 18S rrna 2) The eukaryotic functional equivalent of the prokaryotic 16S rrna is the A) 5S rrna. B) 16S rrna. C) 18S rrna. D) 23S rrna. 3) Carle Woesse is known for his pioneering work in A) The multilocus sequence typing for phylogenetic analys B) The use of SSU rrna for phylogenetic analysis C) The use of multigene and whole genome analysis D) The use of DNA-DNA hybridisation Answer B 4) Which of these steps are correct for identification of an unknown bacteria isolate using multilocus sequence typing? A) isolate DNA, amplify house-keeping gene, sequence gene, BLAST B) isolate DNA, amplify 16S RNA gene, sequence gene, BLAST C) isolate DNA, amplify house-keeping gene, BLAST, sequence gene E) isolate DNA, amplify 16S RNA gene, BLAST, sequence gene Answer A 5) Which of these characteristics is not a typical prokaryotic characteristic A) DNA present in covalently closed and circular B) presence of plasmid DNA C) capping and polytailing of mrna D) Growth above 70 C Answer C 6) Hybridisation of 90% between two isolates indicates that they are A) members of the same species B) members of the same genus but different species C) members of different genera D) none of the above Answer A 7) Which of the following is classified as a pseudomonad A) Ralstonia solanacearum B) Xanthomonas campesteris C) Burkholderia cepacia D) All of the above Answer D

5 8) In the nodule, oxygen levels are controlled by the oxygen binding protein A) haemoglobin B) leghemoglobin C) myoglobin D) oxyhemoglobin Answer B 9) Which of the following groups are NOT able to carry out anoxygenic photosynthesis? A) purple phototrophic bacteria B) purple sulfur bacteria C) purple nonsulfur bacteria D) cyanobacteria D 10) Strains of which genus have had 70% of their genomes hybridized with Escherichia coli? A) Campylobacter B) Salmonella C) Shigella D) Proteus 1C 2C 3B 4A 5C 6A 7D 8B 9D 10C