Micro1_QA1_HIGHLIGHTED.pptx

1.Which of the following is CORRECT with respect to the history of microbiology: a.the order of evolutionary apparence from first to last is: fungi (first), eukaryotes (next), bacteria (last) b.Robert Hooke produced drawings of fungal fruiting bodies in the 150s c.Antoni van Leeuwenhoek described ‘w...

1.Which of the following is CORRECT with respect to the history of microbiology: a.the order of evolutionary apparence from first to last is: fungi (first), eukaryotes (next), bacteria (last) b.Robert Hooke produced drawings of fungal fruiting bodies in the 150s c.Antoni van Leeuwenhoek described ‘wee animalcules’ d.Pasteur was responsible for a series of postulates demonstrating that microbes caused disease e.Koch was the first to disprove the ‘spontaneous generation’ theory History of microbiology Not only did microorganisms survive these conditions they also transformed the earth and its atmosphere making it habitable for plants and animals that arrived much later on Bacteria appeared 4 billion years ago Soon after the earths surface had cooled enough allow liquid water to form Some of them are still capable of living in extreme conditions Eukaryotes: protozoa appeared probably 2 billion years ago Fungi in the last several hundred million years (may have coevolved with plants) 2 Historical roots of microbiology Discovery of microorganisms linked to the invention of the microscope Description of fruiting bodies of moulds 1664 drawings Robert Hooke 1684 Antoni van Leeuwenhoek used simple microscope and described ‘wee animalcules’ 19th century microbiology advanced as microscopes improved 3 Historical roots of microbiology Real advances came in the late 19th century when other basic techniques were devised Major contributions from: Robert Koch Louis Pasteur Pasteur: disproved the ‘spontaneous regeneration’ theory and went on to demonstrate heat sterilisation, and also developed vaccines 4 Historical roots of microbiology Robert Koch: Demonstrated that microorganisms cause disease and developed a set of postulates Also developed culture media for growing bacteria Major advances in the 20th century with the development of molecular biology 5 1.Which of the following is CORRECT with respect to the phylogenetic tree of life: a.Sequencing of the 16S tRNA or the 18s tRNA is employed to generate the information required to generate a phylogenetic tree b.an evolutionary distance is calculated where line length is inversely proportional to the evolutionary distance c.the three major branches on the tree of life are the bacteria, the eukaryea and the archaea d.viruses are located within the tree of life with the ‘host’ that they evolve with e.all life forms contain tRNA and thus tRNA strikes the correct balance between being present in every living organism and having functional constraint placed on the nucleotide sequence Phylogenetic relationships Gene sequencing of 16S or 18S ribosomal RNA enables phylogenetic relationships to be calculated Amplify gene of the ribosomal RNA (rRNA) Computer compares sequences and counts every position where there is a difference ED (evolutionary distance) Construction of tree where length of line proportional to ED 8 9 4. Which of the following is INCORRECT with respect to bacterial populations: a.They are groups of cells that live in a habitat or niche b.They interact with each other in beneficial or harmful ways c.They may have mutualistic, saprophytic or parasitic relationships with their host d.They associate with other populations in microbial communities to form ecosystems e. All of the above are correct Microbial populations Groups of related cells live in a habitat or niche Associate with other populations in microbial communities Form ecosystems Interact with each other in beneficial or harmful ways Competition for nutrients and niches Antagonism production of toxins and antibiotics 12 Microbial populations Cooperation, one group of microorganisms provide nutrients for others: e.g. oral & gut flora Humans have 1013 cells and 1016 microorganisms associated with them Live in water, soil, plants, animals and form the microflora of their habitat Relationship with their host (if they have one) may be mutualistic, saprophytic or parasitic Multiply rapidly, ideal pathogens in or on human cells 13 5. When comparing the leading cause in deaths in the year 1900 and the year 2000, the following statement is CORRECT: a.In the year 1900, the leading cause of death was heart disease b.In the year 2000, the leading cause of death was influenza and pneumonia c.Between the years 1900 and 2000, deaths per 100K due to microorganisms increased d.Between the years 1900 and 2000, deaths per 100K due to microorganisms decreased e.All of the above are correct 16 6. Which of the following statements regarding microbes and their usage in the food industry is INCORRECT: a.Lactococcus lactis is used during the early stages of production of many cheeses. b.Penicillium spp. Is used in the production of various blue cheeses c.Streptococcus bulgaricus is used in the production of yoghurt d.Monosodium glutamate is produced from Corynebacteria glutanicum grown on molasses e.Bacillus anthracis is used during the produce of buttermilk Beneficial Uses of Microorganisms Food Industry: Dairy Products - lactose in milk Metabolised by bacteria to lactic acid Butter: lactic acid starter culture added to cream e.g. Lactococcus cremoris or L. lactis Cheese: Coagulation and fermentation of milk. Addition of other bacteria, Swiss cheese, Propionibacteria Blue cheese, Penicillium sp. 19 Beneficial Uses of Microorganisms Yoghurt: Low fat milk, pasteurised & inoculated with Lactobacillus bulgaricus, Streptococcus bulgaricus Probiotic yoghurts and drinks Bacteria also used in coffee and cocoa preparation Monosodium glutamate is produced from L- glutamic acid from Corynebacteria glutamicum grown aerobically on molasses 20 Beneficial Uses of Microorganisms Vinegar: ethyl alcohol to acetic acid by genera Acetobacter or Gluconobacter Acetobacter oxidising sorbitol produces sorbose used in the manufacture of ascorbic acid Citric acid: fermentation using Aspergillus niger Edible fungi, alcoholic drinks and baked goods - yeasts 21 7. Bacteria are used for various biotechnological purposes including which of the following in a very common employed molecular biological method: a.recombinant DNA polymerase b.recombinant myosin c.recombinant cardiolipin d.recombinant tensin e.recombinant angiotensin Biotechnology Genetic engineering enables gene manipulation and artificial gene products such as insulin Human insulin gene is engineered into a microorganism Recombinant vaccines Thermostable DNA polymerase of Thermus aquaticus known as Taq polymerase, enabled more effective PCR 24 8. Which of the following pairs of bacterial arrangement and genus is CORRECT: a.Palisades : Micrococcus b.Chaining : Streptococcus c.Clusters : Escherichia d.Diploid : Staphylococcus e.All of the above are CORRECT. Bacterial classification Size: measured in microns (1mm = 0.001mm) Bacteria range in size from 0.2mm (Chlamydiae) up to 10mm Smallest are at the limit of resolution of the light microscope Shape (mophology): Cocci Bacilli Ovoid Tapered Curved Spiral Hyphae-like structures May vary within species 27 Bacterial classification Cellular arrangements: Clusters Chains Diploid Tetrads Palisades Motility Presence or absence of spores Growth characteristics: Speed Morphology on selective and non-selective media Atmosphere Temperature 28 Bacterial arrangement 29 9. Which of the following statements regarding the structure of bacterial cell wall is CORRECT: a.Gram-positive cell walls contain two membranes, an inner and an outer b.Gram-negative cell walls contain two membranes, an inner membrane with LPS and an outer membrane composed of phospholipids c.Gram-negative cell walls contain teichoic and lipoteichoic acids d.Gram-negative cell walls contain porins in their outer membrane. e.Gram-positive cell walls contain porins in their inner membrane Gram-positive vs. Gram-negative 32 Overview of G+ and G- 33 Model of G+ and G- cell walls 34 10. The correct order of the Gram staining procedure is: a.fixation, primary stain, counterstain, iodine treatment, decolourisation b.fixation, counterstain, iodine treatment, primary stain, decolourisation c.fixation, primary stain, iodine treatment, decolourisation, counterstain d.fixation, primary stain, iodine treatment, counterstain, decolourisation e.fixation, decolourisation, counterstain, iodine treatment, primary stain Gram staining 37 Differentiation by Gram staining Differences because of the physical nature of the bacterial cell walls Peptidoglycan acts as a permeability barrier preventing loss of the initial stain: crystal violet (CV) Iodine is the second solution to be added Mordant (coordination complex) CV-I complex (larger than CV or I alone) 38 Gram staining Decolourisation step: Thought to shrink the pores of the thick peptidoglycan and CV-I complex retained Gram-negative bacteria have a thin layer of peptidoglycan, with less cross-linking and larger pores CV-I complex removed more easily through G- cell wall 39 Which of the following statements is CORRECT regarding peptidoglycan found in bacterial cell walls (l2): A. It possesses a backbone composed of two repeating sugar molecules: N-acetyl glucosamine (NAG) and Nacetyl glucuronic acid (NAG) B. Individual strands of repeating sugar molecules are cross-linked together by transpeptidase/PBP via the Nacetyl glucosamine (NAG) moieties C. Peptidoglycan provides the cell wall with its overall rigidity D. Crosslinking within peptidoglycan only occurs in two dimensions E. In the case of Gram-positive organisms, crosslinking occurs between teichoic acid and peptidoglycan Peptidoglycan (murein) Common to all types of bacterial cell wall Composed of basic structure of 2 sugar derivatives connected in b1-4 linkages: N-acetyl glucosamine (NAG) N-acetyl muramic acid (NAM) Form a repeating structure called glycan tetrapeptide Glycan chains connected by peptide cross links of 4 amino acids to give rigidity 42 Peptidoglycan 43 Peptidoglycan Cross linking of NAM with a tetrapeptide Characteristic for each specific bacterium In Gram-positive bacteria, cross linking involves a peptide interbridge In S. aureus each interbridge peptide consists of 5 molecules of the amino acid glycine connected by peptide bonds (peptapeptide) 44 Peptidoglycan 45 Peptidoglycan specifics Forms mesh like exoskeleton but is porous enough to allow diffusion of metabolites Essential for survival in hostile conditions Can interfere with phagocytosis, is mitogenic for lymphocytes and has pyrogenic activity b1-4 bond can be degraded by lysozyme 46 Peptidoglycan: diversity Tetrapeptide contains both D and L amino acids (D a.a. not normally used in nature) First 2 amino acids may vary for different organisms 3rd amino acid essential for cross linking D-amino amino acids, include lysine and diaminopimelic acid (DAP) Links to D-alanine in position 4 of another chain 47 Peptidoglycan Precursor form of the peptide has an extra D-ala, which is released during the cross linking step Prefabricated subunits are assembled on the inside of the cell Brought to the surface by a large phospholipid called bactoprenol and attached to the existing structure 48 11.If too little acetone/ethanol is employed during the Gram staining procedure, it is most likely that Gramnegative cells will appear as what colour upon observation: a)Purple or violet b)Pink or fuchsia c)Yellow or golden d)Transparent or unstained e)Green Gram staining 51 Differentiation by Gram staining Differences because of the physical nature of the bacterial cell walls Peptidoglycan acts as a permeability barrier preventing loss of the initial stain: crystal violet (CV) Iodine is the second solution to be added Mordant (coordination complex) CV-I complex (larger than CV or I alone) 52 Gram staining Decolourisation step: Thought to shrink the pores of the thick peptidoglycan and CV-I complex retained Gram-negative bacteria have a thin layer of peptidoglycan, with less cross-linking and larger pores CV-I complex removed more easily through G- cell wall 53 13.Which of the following is CORRECT concerning peptidoglycan? a)The tetrapeptide contains only L-amino acids. b)Peptidoglycan is formed from a repeating backbone of N-acetyl glucoronic acid and N-acetyl muramic acid. c)Crosslinking occurs via the N-acetyl muramic acid moieties. d)In Gram-negative bacteria, cross-linking involves a peptide interbridge. e)The a1-4 bond within peptidoglycan can be degraded by lysozyme. Peptidoglycan (murein) Common to all types of bacterial cell wall Composed of basic structure of 2 sugar derivatives connected in b1-4 linkages: N-acetyl glucosamine (NAG) N-acetyl muramic acid (NAM) Form a repeating structure called glycan tetrapeptide Glycan chains connected by peptide cross links of 4 amino acids to give rigidity 56 Peptidoglycan 57 Peptidoglycan Cross linking of NAM with a tetrapeptide Characteristic for each specific bacterium In Gram-positive bacteria, cross linking involves a peptide interbridge In S. aureus each interbridge peptide consists of 5 molecules of the amino acid glycine connected by peptide bonds (peptapeptide) 58 Peptidoglycan 59 Peptidoglycan specifics Forms mesh like exoskeleton but is porous enough to allow diffusion of metabolites Essential for survival in hostile conditions Can interfere with phagocytosis, is mitogenic for lymphocytes and has pyrogenic activity b1-4 bond can be degraded by lysozyme 60 Peptidoglycan: diversity Tetrapeptide contains both D and L amino acids (D a.a. not normally used in nature) First 2 amino acids may vary for different organisms 3rd amino acid essential for cross linking D-amino amino acids, include lysine and diaminopimelic acid (DAP) Links to D-alanine in position 4 of another chain 61 Peptidoglycan Precursor form of the peptide has an extra D-ala, which is released during the cross linking step Prefabricated subunits are assembled on the inside of the cell Brought to the surface by a large phospholipid called bactoprenol and attached to the existing structure 62 13.The periplasmic space within bacterial cell walls: a)is found only in Gram-negative bacteria b)contains sugar transport proteins c)possesses the chemotaxis system that is coupled to the rotation of the bacterial flagella d)can possess virulence factors e)all of the above are correct Periplasmic space Enzymes include proteases, phosphatases, lipases, nucleases and carbohydrate degrading enzymes Sugar transport systems and binding proteins Components of chemotaxis system, sensing environment outside of the cell In pathogenic bacteria, there will be virulence factors such as collagenases, hyaluronidases, proteases and beta-lactamase 65 13.The outer of the two membranes of bacterial cell walls: a)are found both in Gram-positive and Gram-negative bacteria b)is formed of two phosphoilipid leaflets c)contains lipopolysaccharide (LPS) on its out leaftlet d)is very porous compared to the inner membrane and thus does not require porins. e)makes bacterial cells more sensitive to environmental conditions such as the human digestive system 13.Which of the following is not a unique component of an acid-fast cell wall compared to Gram-positive and Gram-negative cell walls? arabinogalactan mycolic acid lipoarabinomannan N-acetyl glucosamine phosphatidylinositol mannoside (PIM) Acid-fast bacteria Mycobacterium: Have a peptidoglycan layer attached to an arabinogalactan polymer Surrounded by a wax-like lipid coat of mycolic acid, cord factor and wax D Acid-fast staining Interferes with phagocytosis 71 Acid-fast cell wall 72 Cell wall structure/function Gives bacteria: Characteristic shape Protection Transport mechanisms Aids pathogenicity Advantages to man: Classification Provides selective toxicity for anti-microbials 73 Which of the following is INCORRECT regarding lipopolysacchroide (LPS)? a. LPS contains three structural sections: Lipid A, the core polysaccharide and the O polysaccharide. b. Lipid A is anchored within the outer leaflet of the outer membrane. 2.Lipid A consists of 8 fatty acid chains. 3.The core polysaccharide contains 2-keto-3deoxyoctanate (KDO). 4.The O antigen distinguishes serotypes of various bacterial species. LPS 3 structural sections: Lipid A Core polysaccharide O polysaccharide Lipid A anchored in the membrane: Is responsible for the endotoxic activity Very toxic to host Released in large quantities when cells die Consists of 6 fatty acid chains and 2 glucosamine residues 76 LPS Core polysaccharide: Branched and contains 9-12 sugars Contains unusual sugar 2 keto-3-deoxy-octanate (KDO) Core region constant for many species of bacteria O antigen: A long linear polysaccharide of 50-100 repeating saccharide units of 47 sugars per unit Distinguishes serotypes of bacterial species 77 Structure of LPS 78 Which of the following CORRECT regarding flagella antigens and phase variation? Phase variation occurs only in Salmonella species. Bacteria can be typed by their O (flagellar) and H (LPS) antigenic determinants. More than 2000 different Salmonella serotypes exist based on O and H antigens. All of the above are correct. None of the above is correct. Flagella antigens and phase variation Salmonella spp. Typed by their O (LPS) and H (flagellar) antigens >2000 serotypes (different O and H antigens) Have the ability to differentially express the protein antigen as either: Phase 1 or phase 2 - phase variation 81 Which of the following is CORRECT regarding pili and fimbriae? Fimbriae are robust structures that often survive for the entire lifetime of the cell. Both are involved in bacterial motility. Fimbriae tend to be longer, while pili are generally shorter. Both are involved in attachment to host cells. None of the above are correct. Pili and fimbriae Fine hair like filaments on the surface of many Gram negative bacteria Not involved in motility Fimbriae composed from 20 kDa protein Pili generally longer Both involved in attachment of bacteria to host cells Bind to lectins on cell surfaces, e.g sugar binding proteins Gives tissue specificity 84 Pili and fimbriae Bacteria within a human host are constantly losing and reforming fimbriae fragile structures Aid in evasion of the immune system Bacteria, e.g. N. gonorrhoea can change the antigenic structure of their pili / fimbriae. 85