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Nature, Properties and Classification of Micro-organisms

Outline. Importance of microbesNature of bacteria and virusesGram-stain classification of bacteriaVirusesFungiParasites. Importance of Microbes. Life is microbial! (to the first approximation)Micro-organisms colonise every environment on earth>80% of life's history was bacterialYou have more bacterial cells than human cellsMicrobes play a key role in the biospherePathogenic microbes globally are the most important cause of human disease and death.

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Nature, Properties and Classification of Micro-organisms

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    1. Nature, Properties and Classification of Micro-organisms Professor Mark Pallen

    2. Outline Importance of microbes Nature of bacteria and viruses Gram-stain classification of bacteria Viruses Fungi Parasites

    3. Importance of Microbes Life is microbial! (to the first approximation) Micro-organisms colonise every environment on earth >80% of life’s history was bacterial You have more bacterial cells than human cells Microbes play a key role in the biosphere Pathogenic microbes globally are the most important cause of human disease and death

    4. Importance of Infection Decisive role in history Still major cause of death and misery worldwide Public anxieties Meningitis, Food poisoning Mad cow disease Emerging infections Hospital Infection Antibiotic-Resistant Superbugs

    5. Microbes in History

    6. Microbes in History

    7. Microbes in the News

    8. Microbes in the News

    9. Microbes in the News

    10. Microbes in the News

    11. Microbes in the News

    12. Differences between Bacterial and Human Cells Bacterial cells No nucleus No intracellular organelles (but ribosomes) No introns (nearly) No junk DNA Plasmids, bacteriophage Human cells Nucleus Intracellular organelles (ribosomes subtly different) Introns Lots of junk DNA Viruses

    13. Tree of Life

    14. Size matters

    15. Bacterial cells

    16. Differences between bacteria and viruses Viruses Obligate intracellular parasites No ribosomes DNA or RNA, not both seen by EM 10-100s of genes Tangled phylogeny Bacteria Usually free-living, but can be parasites Ribosomes DNA and RNA seen by LM 100s-1000s of genes Natural phylogeny

    17. The Gram stain procedure

    21. Bacterial Growth Solid media or liquid media Agar plates, slopes, broth culture Atmosphere: Aerobic, anaerobic or microaerophilic Facultative or obligate anaerobes Usually at 37 degrees C Most clinically important bacteria grow overnight, or within a few days Mycobacteria can take months Some can not be grown

    22. Gram-Negative Rods Enteric Bacteria E. coli Salmonella Shigella Yersinia Pseudomonas Proteus Vibrio cholerae Klebsiella pneumoniae

    23. Gram-Negative Rods Fastidious GNRs Bordetella pertussis Haemophilus influenzae Campylobacter jejuni Helicobacter pylori Legionella pneumophila Anaerobic GNRs Bacteroides fragilis Fusobacterium

    24. Gram-Negative Cocci Neisseria gonorrhoeae The Gonococcus Neisseria meningitidis The Meningococcus Both Gram-negative intracellular diplococci

    25. Gram-positive Cocci Staphylococci Catalase-positive Gram-positive cocci in clusters Staphylococcus aureus coagulase-positive Staph. epidermidis and other coagulase negative staphylococci

    26. Gram-Positive Cocci Streptococci Catalase-negative Gram-positive cocci in chains or pairs Strep. pyogenes Strep. pneumoniae Viridans-type streps Enterococcus faecalis

    27. Gram-Positive Rods Clostridia Anaerobes C.perfringens C. tetani C. botulinum C. difficile Bacillus cereus Aerobe Listeria monocytogenes Faculative anaerobe

    28. Non-Gram-stainable bacteria Unusual gram-positives Spirochaetes Obligate intra-cellular bacteria

    29. Unusual Gram-positives Mycoplasmas Smallest free-living organisms No cell wall M. pneumonia, M. genitalium Mycobacteria Acid-fast bacilli, stained by Ziehl-Neelsen stain M. tuberculosis M. leprae M. avium

    30. Spirochaetes Thin spiral bacteria Viewable by phase-contrast microscopy or silver stain Treponema pallidum Borrelia burgdorferi Leptospira

    31. Obligate intracellular bacteria Rickettsia Coxiella burneti Chlamydias C. trachomatis C. pneumoniae C. psittaci

    32. Viruses No natural taxonomy probably chimaeric and/or derived mutiple times from host genomes Classified according to genome type: DNA or RNA Polymerase: some use reverse transcriptase to make DNA from RNA whether they have envelope or not

    33. DNA Viruses Herpes Viruses Herpes simplex 1 & 2 Varicella-zoster Cytomeglaovirus Epstein-Barr virus Pox viruses Smallpox Vaccinia Orf

    34. DNA Viruses Papilloma viruses Adenovirus Human parvovirus B19 Hepatitis B (but odd life cycle, uses reverse transcriptase)

    35. RNA Viruses Picornaviruses Rhinovirus Polio virus Hepatitis A Coxsackie ECHO

    36. RNA Viruses Orthomyxoviruses Influenza Paramyxoviruses Measles, mumps, parainfluenza, RSV Rubella Rabies Hepatitis C

    37. RNA Viruses Retroviruses HIV1, HIV2 HTLV 1, HTLV 2

    38. Prions Proteinaceous infectious particles Apparently an infectious form of a protein, with no nucleic acid Still enigmatic BSE, CJD, Kuru, Scrapie, nv-CJD

    39. Fungal Pathogens Yeast-like fungi Candida albicans Cryptococcus neoformans Filamentous fungi (moulds) Aspergillus fumigatus Dermatophytes Unusual fungi Pneumocystis carinii

    40. Parasites Protozoal, e.g. Giardia Entamoeba Plasmodium Schistosoma Metazoan, e.g. Worms Flukes Ectoparasites

    41. Summary Importance of microbes Nature of bacteria and viruses Gram-stain classification of bacteria Viruses Fungi Parasites

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