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Bacteriology Part 1 for undergradu.pptx
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- 2. 2 Taxonomy / Systematics •Nomenclature – Providing a formal name – Genus & species • Ford Crown Victoria • Chevy Impala • Toyota Camry • Honda Civic • Classification • Organization into groups • Car • Truck • SUV • Van • Identification • Distinguishing features • Engine size • Mileage • Number of passengers • Type of transmission Consistent rules for all scientist Relevant Meaningful Make biological sense Evolutionary context
- 3. 3 Five Kingdoms Bacteria Archaea Prokaryotic Unicellular Eukaryotic Unicellular Uni ormulticellular Eukaryotic
- 4. 4 Bacteria Archaea Eukarya 3Domain System Carl Woese Late 1970’s & early 1980’s Woese, C. R. 2004. A New Biology for a New Century. MMBR. June 68(2):173-86. Woese, C.R. 2002. On the evolution of cells. Proc Natl Acad Sci USA 99(13):8742-7. Woese, C.R. 2000. Interpreting the universal phylogenetic tree. Proc Natl Acad Sci USA 97(15):8392-6.
- 5. 5 Binomial nomenclature Genus &species Escherichia coli Genus name is always capitalized Species name is never capitalized coli Both names are always either italicized or underlined Abbreviation: E. coli
- 6. 6 Domains can beDivided into Many Sub-classifications • Domain: Bacteria • Phylum: Proteobacteria • Class: Gamma Proteobacteria • Order: Enterobacteriales • Family: Enterobacteriaceae • Genus: Escherichia • Species: Escherichia coli Biological species concept does not apply to prokaryotes!!!
- 7. 7 strain or variety– a culture derived from a single parent that differs in structure or metabolism from other cultures of that species (biovars, morphovars) type – a subspecies that can show differences in antigenic makeup (serotype or serovar), susceptibility to bacterial viruses (phage type) and in pathogenicity (pathotype) Species – a collection of bacterial cells which share an overall similar pattern of traits in contrast to other bacteria whose pattern differs significantly
- 8. Classification of Bacteria -Light microscope was the original tool. - Initial classification was based on of the shape of the bacterial cells.
- 9. 9 4 Main Shapesof Bacteria • Cocci • Bacilli • Spirilla • Spirochetes
- 10. 10 Medical Microbiologists said… Onebacterium = One disease So to these scientists, bacteria were also classified as to the disease they caused… They were also named based on this…
- 11. 11 Four (4) GroupsBased on Cell Wall Composition 1. Gram-positive cells 2. Gram-negative cells 3. Bacteria without cell walls 4. Bacteria with chemically unique cell walls
- 12. 12 Peptidoglycan • Macromolecule composedof a repeating framework of long chains cross-linked by short peptide fragments – Unique to Bacteria – Composed of 2 sugars: NAG & NAM – Sugars alternate in the backbone – Rows linked by polypeptides • Provides strong, flexible support to keep bacteria from bursting or collapsing because of changes in osmotic pressure N-acetylglucosamine (NAG) N-acetylmuramic acid (NAM)
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- 14. 14 Gram Positive CellWall • Consists of – A thick, homogenous sheath of peptidoglycan 20 - 80 nm thick – Tightly bound acidic polysaccharides, including teichoic acid and lipoteichoic acid – Retains crystal violet with iodine as a mordant
- 15. 15 Gram Negative CellWall • Consists of – An outer membrane containing lipopolysaccharide (LPS) – Thin shell of peptidoglycan between inner and outer membranes – Periplasm – Inner membrane – Loses crystal violet-iodine complex when cells are exposed alcohol (decolorization step) and stains red with safranin counterstain
- 16. 16 Be able toidentify all the parts of a Gram + & - cell wall the next exam.
- 17. 17 Bacteria with ChemicallyUnique Cell Walls • Acid-Fast Cells • Mycobacterium species • Gram + type of cell wall • Unique lipid – Mycolic acid – waxy substance • Does not decolorize
- 18. 18 Rickettsia – ChemicallyUnique Cell Wall • Stains Gram - • Cell wall contains diaminopimelic acid & lacks teichoic acid • 0.25 m in diameter • Obligate intracellular pathogens – Encapsulated – Enter cell by induced phagocytosis – Divide rapidly once inside • Pathogens that alternate between mammals and fleas, lice or ticks – Rickettsia rickettisii – Rocky Mountain spotted fever – Rickettsia prowazekii – epidemic typhus – Coxiella burnetti – Q fever
- 19. 19 Chlamydia – ChemicallyUnique Cell Wall • Obligate intracellular parasites • 0.3 and 1.0 m in diameter • Cell wall contains an outer lipopolysaccharide membrane but lacks peptidoglycan – Contains cysteine-rich proteins that are assumed to be the functional equivalent of peptidoglycan – Stains Gram - • Chlamydia trachomatis – The most common sexually transmitted disease • Chlamydia psittaci – Ornithosis, parrot fever • Chlamydia pneumoniae – Lung infection
- 20. 20 Bacteria without CellWalls - Mycoplasma • Lack a rigid cell wall during their entire life cycle • Smallest known organisms – smallest genomes (other than viruses) –Diameter ranges from 0.15 m to 0.30 m • Do not stain with the Gram stain • Pleomorphic –Tiny pleomorphic cocci, short rods, short spirals, and sometimes doughnut shape • Mycoplasma pneumoniae – Atypical pneumonia in humans
- 21. 21 Numerical Taxonomy Looked atall traits of an organism… every trait had equal importance
- 22. 22 rRNA Sequence • Thegreatest advancement in classifying organisms • Differences in the nucleotide sequence are used to classify prokaryotes • 16S rRNA sequences • 23S rRNA sequences Actually look at the DNA that codes for the rRNA
- 24. 24 How is thisaccomplished? Extract DNA from a colony, or from an environmental sample without growing the organism. PCR with primers for rRNA sequences Automated DNA sequencer Coefficient of Similarity
- 25. Bacteria phylogenetic relationshipsbased on rRNA sequences
- 26. 26 Phylogenetic tree of 16SrDNA sequences Texas A&M Microbiology www-odp.tamu.edu/.../ 203/images/03_f03b.gif Coefficient of Similarity
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- 28. 28 Bergey’s Manual ofSystematic Bacteriology • Prokaryotes into 25 phyla – Archaea • 2 – Bacteria • 23 • Consensus of experts
- 29. 29 rRNA Sequence • Thegreatest advancement in classifying organisms • Differences in the nucleotide sequence are used to classify prokaryotes • 16S rRNA sequences • 23S rRNA sequences Actually look at the DNA that codes for the rRNA Relevant Meaningful Make biological sense Evolutionary context
- 30. A Selection ofBiologically Important Groups of Bacteria These groups have been traditionally defined by cell shape, metabolism, method of motility or type of infection.
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- 32. 32 Cyanobacteria • Gram negativephototrophs – Oxygenic photosynthesis 12H2O + 6CO2 C6H12O6 + 6H2O + 6O2 – Existed for 2.3 bya – Largest and one of the most important groups of bacteria on Earth • Extremely diverse group – Unicellular, colonial & filamentous form – Some species fix N2 in heterocysts – Some species produce akinete • Analogous to a endospore Most species are found in fresh water • Marine • Damp soil • Temporarily moistened desert rocks • Endosymbionts in lichens, plants, various protists or sponges
- 33. 33 Heterocysts N2 fixation Internal photosynthetic membrane Somecyanobacteria can fix nitrogen
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- 35. 35 Spirochetes • Long, helicallycoiled cells. • Gram – • Axial filaments – Running lengthwise between the cell membrane and cell wall – Most spirochetes are free-living and anaerobic, but there are exceptions • 3 families • Leptospira spp. – Leptospirosis • Borrelia burgdorferi – Lyme disease • Treponema pallidum – syphilus www.bbc.co.uk/.../stis_syphilis.shtml www.microbeworld.org Borrelia burgdorferi
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- 37. 37 Enterics • Gram –rods, facultative anaerobes • Family Enterobacteriaceae • Many are part of the intestinal microflora of mammalian intestines • Infamous pathogens – Salmonella, Escherichia, Klebsiella, Proteus, Enterobacter, Citrobacter • Most ferment glucose, reduce nitrates to nitrites and oxidase negative • Many diagnostic tests to identify these organisms – Page 615 & 616 – Table 20.2
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- 39. 39 Magnetotactic • Magnetosome – Crystallineparticles of iron oxide or sulfide – Magnetite Fe3O4 – Greigite Fe3S4 • All are either obligate microaerophiles or strict anaerobes • Motile, aquatic bacteria • Direction of motility is affected by the Earth’s geomagnetic field • Strains are either north- or south-seeking depending upon oxic conditions – North-seekers predominate in the northern hemisphere – South-seekers predominate the southern hemisphere – Exist in equal numbers at the equator • Current hypothesis states that these bacteria use the geomagnetic field to locate lower O2 or anaerobic habitats
- 40. 40 There are TwoTypes of Magneto- aerotaxis... Axial Magneto- aerotaxis Polar Magneto- aerotaxis e.g., Magnetospirillum magnetotacticum e.g., strain MC-1, a magnetotactic coccus
- 41. 41 N2 Fixation • Archaea& Bacteria • Nodules – Rhizobium and Bradyrhizobium form nodules on the roots of legumes – Frankia forms nodules on the roots of alders (Alnus), wax myrtles (Myrica) and mountain lilacs • “pioneer plants” • Free-living – Azospirillum – Azotobacter – Clostridium – Bacillus – Klebsiella – Methanosarcina • Archaea – Cyanobacteria • No eukaryotic organisms fix N2 www.tari.gov.tw/ARI_E/E_image/ACD_13.jpg
- 42. 42 Pyogenic cocci • Causesmany suppurative infections • Gram + cocci – Staphylococcus aureus, Streptococcus pyogenes & Streptococcus pneumoniae, • Gram - cocci – Neisseria gonorrhoeae & N. meningitidis • ⅓ of all human bacterial infections – Food poisoning, strep throat, pneumonia, various skin diseases, septic shock, gonorrhea & meningitis • Bacteria in this group are unrelated mdchoice.com/photo/img/img0110.jpg nova.medicina.cz/files/ gonorrhea_01.jpg
- 43. 43 Lactic Acid Bacteria •Fementative bacteria that produce lactic acid under anaerobic conditions (can be described as oxytolerant anaerobes) – Convert pyruvate to lactic acid • Also produce acetic acid & CO2 – Regenerate NAD+ for glycolysis • Species of Streptococcus and Lactobacillus • Dairy industry – Cheese, cottage cheese, yogurt
- 44. 44 Endospore-forming Bacteria • Gram+ – Bacillus, Clostridium and Sporosarcina • Survival structure – Resistant to heat, UV, desiccation • Pathogen – Bacillus anthracis – Clostridium tetani – C. perfringens – C. botulinum
- 45. 45 Purple and GreenBacteria • Anoxygenic photosynthesis – 12H2S + 6CO2 C6H12O6 + 12S° • Colors due to color of slightly different bacteriochlorophylls – Green - deposit S° outside – Purple - S° is inside the cell • Anaerobic H2S-containing mud and water
- 46. 46 Vibrios • Gram -,slightly curved rods, polar flagellum • Estuarine & marine environments • Pathogenic and cooperative interactions with eukaryotic host • Vibrio cholerae – Cholera • Extreme watery diarrhea – Only species that can survive in both fresh and salt water – Potent toxin • Vibrio fischeri – Bacterial bioluminescence – Lives planktonically in seawater but can also colonizes organs of squids and marine fish – Autoinducer – Quorum sensing ergo.integratedgenomics.com www.nature.com/.../020603/full/020603-2.html
- 47. 47 Myxobacteria • Glide oversurface – No flagella • Vegetative cells swarm during nutrient depletion • Fruiting body • Dormant myxospores • Spores “germinate” under favorable conditions www.textbookofbacteriology.net
- 48. 48 Actinomycetes • Filamentous, Gram+ soil bacteria • Aerobic decomposition of organic compounds – Biodegradation – Carbon cycle • Geosmins – Earth odor • Antibiotics – Streptomyces – Tetracyclines, macrolides and aminoglycosides • Pathogens – Mycobacterium tuberculosis – Corynebacterium diphtheriae
- 49. 49 Radioresistant • Deinococcus radiodurans –Gram + • Survive a dosage of radiation that is 3,000 times greater than what would kill a human • Survive DNA damaging chemicals, and high levels of ionizing and ultraviolet radiation, and dehydration • Able to repair chromosome fragments within 12-24 hours – Repair chromosomes that have been broken into 100 fragments science.nasa.gov