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11/13/2010 LS 204 Microbiology Chapter 7 Student Learning Outcomes: • 1. Name some organisms that are microorganisms • 2. Explain the importance of microorganisms to our everyday lives • 3 3. Describe the importance of and differences between D ib h i f d diff b viruses, viroids, and prions • 4. Discuss why it is important to understand the growth requirements, metabolism, and genetics of bacteria • 5. Explain how microbes cause disease and how we control them, both inside and outside of the body Questions starting: • What sorts of organisms would be called microorganisms – give examples • What are some ways we benefit from microbes? • What is a virus? • How do bacteria divide? • What are some ways the human body defends itself against disease? 1 11/13/2010 Examples of microorganisms of 3 Domains (Fig. 7.1): • Bacteria Archaea Eukarya Example microorganisms of the three Domains • Domain Archaea = prokaryotes; ‘extremophiles’; Halobacterium; Pyrococcus No human pathogens; many unusual metabolic patterns • Domain Bacteria = prokaryotes; Escherichia coli, Staphylococcus aureus; Bacillus anthracis Beneficial organisms and human pathogens; also unusual metabolic patterns • Domain Eukarya: • • • • Kingdom Protista – pathogens like Amoeba, Trypanosoma, Kingdom Fungi – pathogens include yeast like Candida Kingdom Animalia – worms include Schistosoma Kingdom Plantae – algae like Chlamydomonas Importance of microorganisms • Pathogens cause disease in humans, other organisms • Beneficial organisms: • cyanobacteria and algae in oceans do photosynthesis and produce sugar and oxygen h t th i d d d • fungi and Bacteria recycle waste products, organic molecules, oil spill • fungi and Bacteria produce food and drinks (yoghurt, beer, wine) • normal microbiota = microbes on our skin, digestive system that protect from pathogens 2 11/13/2010 Naming microbes • Bacteria = Domain Bacteria; • bacteria = prokaryotes, includes Domain Archaea • 1 bacterium, 2 bacteria • • • • • Binomial nomenclature: Species genus ex. Escherichia coli Spell out genus first time it’s used, Afterwards, can abbreviate: E. coli Write names in italics Hierarchy in Domain Bacteria • The groupings help understand shared characteristics, antibiotics that will kill them • Ex Ex. E. coli is Domain Bacteria, Phylum E coli is Domain Bacteria Phylum Proteobacteria; Family Enterobacteriaceae • Family includes other intestinal inhabitants and pathogen genera such as Salmonella, Enterobacter, Shigella) Names can reflect shapes, sizes, arrangement of cells • Coccus (cocci plural) = round • Bacillus (bacilli) = rod • Spirilla = spiral‐shaped • Strepto = chains • Staphylo = clusters • • Diplo‐ = two 3 11/13/2010 Names can indicate properties • Escherichia coli Eponym for Dr. Escher; coli for colon • Micrococcus roseus small red circles • Mycobacterium tuberculosis waxy cell walls causes tuberculosis (tubercles in lungs) waxy cell walls, causes tuberculosis (tubercles in lungs) • Streptococcus pneumonia round cells in chains, causes pneumonia • Bacillus megaterium • Thiobacillus very large rod‐shaped organism rod‐shaped organism that eats sulfur More microbes: Viruses, Viroids, Prions HPV • Not considered ‘living’ since not cells, lack ability to reproduce on own (use host resources). • Virus (Fig. 7.4) has nucleic acid (DNA OR RNA) wrapped in ( g ) ( ) pp protein coat • Some also have envelope (made of host’s membrane with viral proteins) • [Bacteriophages infect bacteria] • Animal viruses infect animals Virus examples Shapes of virus capsids herpesvirus 4 11/13/2010 Virus quantification Plaque assay – grow viruses on lawn of susceptible host cells; Infection of host cell, replication and infection of adjacent cells ‐> hole or plaque Virus life cycle (Fig. 7.4): • Attachment: specific molecules on virus and receptors on host • Penetration: all or some of virus enters • Uncoating: protein coat removed • Biosynthesis: of viral nucleic acids and Bi th i f i l l i id d proteins • mRNA ‐> proteins using host ribosomes; • DNA or RNA of genome is reproduced • Release: virus breaks out of cell or buds through membrane Virus life cycle (Fig. 7.4) Herpesvirus A DNA virus 5 11/13/2010 Retrovirus life cycle (Fig. 7.4) HIV (Human immunodeficiency virus) A retrovirus: RNA genome, converts to DNA • Viroid : nucleic acid only – some plant diseases • Prions – only protein – animal diseases: • Spongiform encephalopathy (Mad Cow disease, elk wasting disease) Creutzfeld‐Jacob disease (CJD) Examples of microorganisms of 3 Domains (Fig. 7.1): • Bacteria Archaea Eukarya 6 11/13/2010 How bacteria work tiny factories of only 1 cell compartment • Growth and nutrition: • Divide by binary fission (Fig. 7.5) – 1 cell ‐>2 cells ‐> 4 cells • Many different metabolic, nutrition patterns – more diverse than eukaryotes • Latin terms refer to metabolic patterns: How bacteria work tiny factories of only 1 cell compartment • Producers include Photoautotrophs (photosynthesis, use CO2 + H2O to make sugars + O2) cyanobacteria • Human pathogens are mostly Mesophiles (grow at middle temperatures) • Some bacteria are thermophiles (high temperatures) • Some bacteria are psychrophiles (low temperatures) Oxygen requirements: • obligate aerobes (skin, lungs) – Pseudomonas aeruginosa • facultative anaerobes (gut) – Escherichia coli • obligate anaerobes (puncture wound) – Clostridium tetani 7 11/13/2010 • Metabolism: similar to eukaryotes, especially for pathogens, but only 1 compartment • Catabolism to take apart molecules and gain ATP building blocks; ATP, building blocks; • Anabolism uses ATP and small molecules to build macromolecules Typical metabolism: Glycolysis: 6C sugar (glucose) ‐> to 3‐C pyruvate + ATP + NADH (e‐ carriers) • occurs in cytoplasm of bacteria and eukaryotes Krebs cycle (citric acid cycle): 3‐C pyruvate ‐> CO2 + ATP + NADH + FADH2 Electron transport chain (aerobic respiration): • NADH + FADH2 + O2 ‐> lots of ATP + H2O + NAD + FAD • Occurs in cytoplasm of bacteria; mitochondria of eukaryotes Metabolism cont. Fermentation: alternative path that does not require oxygen: occurs in cytoplasm • Pyruvate ‐> an organic molecule; a low energy path that recycles the NADH • Yeast make alcohol + CO2; (muscle cells lactic acid) • Bacteria make lactic acid, butyric acid, other products • (Fig. 7.6 concept map of relationships of pathways) 8 11/13/2010 Microbial Genetics DNA ‐> RNA ‐> protein (Fig. 7.7) • Transcription is DNA copied into rRNA, tRNA or mRNA • Translation is synthesis of protein from mRNA on the ribosome Examples of microorganisms of 3 Domains (Fig. 7.1): • Bacteria Archaea Eukarya Bacterial gene transfer Bacteria can transfer some genes from one to another (even between species) (Fig. 7.8): • Transformation = piece of DNA can go into another cell • Transduction = piece of bacterial DNA packaged in bacteriophage coat goes into other cell • Conjugation = two bacteria attach and one donates copy of some genes *** Antibiotic‐resistant bacteria can transfer these genes to other bacteria 9 11/13/2010 Bacterial gene transfer methods Microbial control – how we control them. • Physical and chemical agents: • Disinfectants • Sterilants (gas, autoclave) • Sanitizers • Radiation • Chemotherapeutics (antibiotics) – compounds taken inside us to kill them Principles of disease • Each pathogen has its niche – temperature, humidity, cell type, oxygen • Epidemiology – study of epidemics, or sudden large numbers of cases of disease in population. p p • Epidemiologists look for patterns of disease, moniter numbers • Note Latin terms, name of disease for body part: • meningitis = inflammation of meninges • bacteremia = bacteria in the blood system 10 11/13/2010 Defenders against disease (Table 7.9) • Innate immunity (nonspecific) • First line = intact skin, mucus membranes, normal microbiota • Second line = natural killer cells phagocytic white blood cells, inflammation, fever Adaptive (specific) immunity • Specialized lymphocytes: T cells and B cells • Antibodies produced by B cells circulate in blood stream • Antibodies recognize Antibodies recognize specific antigens (structures) on the pathogen • Vaccines stimulate production of ‘memory’ T cells and B cells to defend future infection 11