Microbiology - Week 4 - Lecture 1 - Introduction to Microbial Diversity 2023.pdf

INTRODUCTION TO MICROBIOLOGY I A REVIEW OF MICROBIAL DIVERSITY W H AT I S MICROBIOLOGY? A good first question! W H AT W E ’ L L BE LOOKING AT … Organisms and biological entities studied by microbiologists can be A tree of microbial life. Fungi Cellular Acellular includes includes Protists Bacteria A...

INTRODUCTION TO MICROBIOLOGY I A REVIEW OF MICROBIAL DIVERSITY W H AT I S MICROBIOLOGY? A good first question! W H AT W E ’ L L BE LOOKING AT … Organisms and biological entities studied by microbiologists can be A tree of microbial life. Fungi Cellular Acellular includes includes Protists Bacteria Archaea Viruses Viroids Satellites Prions composed of composed of e.g. e.g. e.g. e.g. composed of composed of Yeasts Molds Algae Protozoa Slime molds Escherichiɑ coli Methanogens Protein and nucleic acid RNA Nucleic acid enclosed in a protein shell Protein 7 KEY GROUPS OF MICROORGANISMS Bacteria Archaea Fungi Protozoa Algae Small multicellular animals Viruses(?) HOW TO SORT SPECIES? Type of cell? Type of cell wall? Mode of nutrition? Mode of motility? Reproductive mode? DNA sequences PROKARYOTIC CELLS No nucleus No membrane-bound organelles Circular chromosomes Asexual reproduction Unicellular/colonial Usually small BACTERIA Peptidoglycan cell wall (some species lack cell wall) A few species are harmful to humans; most are neutral or beneficial. Methanogens ARCHAEANS Non-peptidoglycan cell wall Ribosomal structure closer to eukaryotes Often found in extreme environments None associated with disease Extreme Halophiles THE E U K A R YOT E S Protists, algae, fungi, plants, animals P R O K A R YOT E S V S E U K A R YOT E S Key comparisons Feature Prokaryotes Eukaryotes Organization Usually unicellular Unicellular, colonies, multicellular Size 1-10µm 10-100µm (Sometimes more) Type of nucleus DNA housed in a ‘nucleoid region’ Proper nucleus with a double membrane DNA Usually circular Linear chromosomes Cell Movement Flagella (made up of Flagellin Protein) Cilia, Pseudopodia Membrane bound organelles None Many FUNGI Absorptive heterotroph Cell wall made up of chitin Multicellular or unicellular Penicillium chrysogenum Saccharomyces cerevisiae PROTOZOANS … NOT Protists Single-celled eukaryotes with animal-like digestion (ingestive heterotrophs) Often sorted according to mode of motility PA R A S I T I C P R OTO Z O A N S Leishmania (Leishmaniasis) Trypanosoma (African sleeping sickness) Plasmodium (malaria) Giardia (Giardiasis) ALGAE Unicellular or multicellular, eukaryotic photosynthetic autotrophs Categorized the basis of their pigmentation and the composition of their cell walls Multicellular – seaweed and kelp; No roots; all tissues are photosynthetic Spirogyra Diatoms Lake in Guatemala ALGAL BLOOMS Red Tide (dinoflagellates) ANIMALS Ingestive heterotroph Adults visible but larvae are microscopic Blood fluke (Schistosomiasis) Tapeworm Ascaris (Ascariasis) INTRODUCTION TO MICROBIOLOGY II A B R I E F H I S TO R Y O F MICROBIOLOGY Prepared by: Nick Inglis, Ph.D. HISTORY OF MICROBIOLOGY AND DISEASE 400 BC: Hippocrates considers a link between environment and disease Thucydides notes plague survivors cannot get the same disease twice And then … nothing for 2000 years? ROBERT HOOKE (1650S): THE FOUNDER OF CELL BIOLOGY Introduced the notion that cells were the fundamental unit of life. Coined the term ”cell” due to resemblance to honeycomb cells ANTONIE VAN LEEUWENHOEK (1670S): THE FOUNDER OF MICROBIOLOGY Leeuwenhoek first reported the existence of most types of microorganisms Lens Specimen holder VAN LEEUWENHOEK’S DISCOVERIES: 1674: PROTISTS Protist: any eukaryotic organism that is not an animal, plant, or fungus. VAN LEEUWENHOEK’S DISCOVERIES: 1676: FIRST BACTERIAL CELL Albeit large ones (Selenomonads) VAN LEEUWENHOEK’S DISCOVERIES: 1677: VERTEBRATE SPERM CELLS Also first to document: spermatozoa, muscle fibers, red blood cells Homunculus “Little man” CAROLUS LINNAEUS (1735): THE FOUNDER OF TAXONOMICS Taxonomics – a system for naming species and grouping similar ones together Linnaeus described two groups: Animals and Plant Species: Panthera pardus Genus: Panthera Family: Felidae Order: Carnivora Class: Mammalia Phylum: Chordata Kingdom: Animalia HIERARCHICAL (LINNAEN) CLASSIFICATION 7 levels—taxon (Plural – taxa) Binomial Nomenclature: naming includes 2 terms— genus and specific epithet HOW DOES LIFE EMERGE? Aristotle (ca 350 BC) – the theory of abiogenesis or spontaneous generation – life emerging from non-living matter. FRANSISCO REDI (1668) – PUTTING SPONTANEOUS GENERATION IN QUESTION Flask unsealed Flask sealed Flask covered with gauze JOHN NEEDHAM (1750) – SUPPORTING SPONTANEOUS GENERATION As he explained it, “there must be a “life force” that causes inanimate matter to spontaneously come to life because he had heated the vials sufficiently to kill everything.” PASTEUR (1861): SWAN-NECKED FLASK EXPERIMENT Steam escapes from open end of flask. Infusion is heated. Air moves in and out of flask. Infusion sits; no microbes appear. Months Infusion remains sterile indefinitely. He concluded that the microbes in the liquid were the progeny of microbes that had been on the dust particles in the air. Dust from air settles in bend. A MODERN DAY VERSION OF PASTEUR’S EXPERIMENT PASTEUR AND FERMENTATION Observation: What causes the fermentation of grape juice into wine? What causes spoiling? Microscopic analysis shows juice contains yeasts and bacteria. Fermenting grape juice Hypothesis Experiment Day 1: Flasks of grape juice are heated sufficiently to kill all microbes. I. Spontaneous fermentation occurs. II. Air ferments grape juice. III. Bacteria ferment grape juice into alcohol. IV. Yeasts ferment grape juice into alcohol. Observation Day 2 Flask is sealed. Flask remains open to air via curved neck. Juice in flask is inoculated with bacteria and sealed. Juice in flask is inoculated with yeast and sealed. Conclusion No fermentation; juice remains free of microbes Reject hypothesis I. No fermentation; juice remains free of microbes Reject hypothesis II. Bacteria reproduce; acids are produced. Modify hypothesis III; bacteria ferment grape juice into acids. Yeasts reproduce; alcohol is produced. Accept hypothesis IV; yeasts ferment grape juice into alcohol. PASTEUR’S FINAL CONTRIBUTION Pasteurization: heating grape juice just enough to kill most bacteria without ruining the juice’s taste and other qualities PASTEUR’S 1857 HYPOTHESIS: Germ theory of disease microorganisms are also responsible for disease Each disease is caused by a specific germ (pathogen) Diseases caused by germs are now called infectious diseases ROBERT KOCH (1843-1910): STUDYING THE ETIOLOGY OF INFECTIOUS DISEASE Simple staining techniques First photomicrograph of bacteria First photograph of bacteria in diseased tissue Use Petri dish to hold solid growth media Transferring bacteria with heat and metal wires BACTERIAL COLONIES ON A CULTURE DISH Bacterium 6 Bacterium 7 Bacterium 8 Bacterium 5 Bacterium 4 Bacterium 3 Bacterium 2 Bacterium 1 Bacterium 9 Bacterium 10 Bacterium 11 Bacterium 12 KOCH’S POSTULATES 1. The suspected causative agent must be found in every case of the disease and be absent from healthy cases 2. The agent must be isolated and grown outside the host 3. When the agent is introduced to a healthy, susceptible host, the host must get the disease 4. The same agent must be found in the diseased experimental host. THE PREVENTION OF DISEASE: 1. HANDWASHING Ignaz Semmelweis (1848) – observed that women giving birth where medical students trained died from puerperal fever 20X more than women birthing at home Hypothesized it was due to cadaver particles in med students Handwashing with chlorinated lime water decreased mortality THE PREVENTION OF DISEASE: 2. JOSEPH LISTER (1850S) Introduced antiseptic technique and disinfection into surgical theatres Sprayed phenol on incisions, wounds, dressings, etc. THE PREVENTION OF DISEASE: 3. FLORENCE NIGHTINGALE (1850S) Introduced antiseptic techniques into nursing practices (Crimean War)—scrubbing furniture, equipment, changing clothes, dressings… Detailed statistical studies connecting poor food and unsanitary conditions in hospitals to deaths of soldiers. THE PREVENTION OF DISEASE: 4. JOHN SNOW (1854) Successfully correlated cholera propagation with poor water sanitation. Led to emergence of 2 major branches of microbiology 1. Infection control 2. Epidemiology THE PREVENTION OF DISEASE: 5. VARIOLATION (1720’S) The problem: smallpox Caused by two viral variants: Variola Major and Variola Minor 1500-1800: Variolation was common practice Total patients Died % Mortality Variolated ~300 6 ~2% Unvariolated ~6000 ~1000 ~14% Natural Experiment, Boston, 1720s THE PREVENTION OF DISEASE: 6. JENNER’S VACCINE (1790S) Jenner’s observations: milkmaids did not get smallpox Injected 8 year old boy with pus from milkmaid’s cowpox blisters Weeks later, he injected the boy with Variola major (bad ethics!) THANKS! S E E YO U S O O N !