Microbiology Exam 1 – Donaldson – Flashcards
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| Microbe |
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| single cell organism range in size from mm to nm; can only see individual cells through a microscope not all are bad- bacteria in stomach not all can survive alone- biofilms (community of bacteria) or viruses |
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| Major advancements had to be made in order sto study microorganisms |
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| Microscopes powerful enough to observe microbes Molecular Biology Sequencing of genomes |
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| Robert Hooke |
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| Built first compound microscope Looked at piece of cork under microscope First to describe cells, but never observed single celled organisms Published findings in Micrographia in 1665 |
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| Anton van Leeuwenhoek |
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| Father of microbiology improved the microscope to be able to observe single celled organisms Referred to them as "animal cubes" First to describe how heat can kill microbes (coffee) Died from bacteria he was observing |
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| Franscesco Redi, Lazzaro Spallanzani, Louisi Paseur |
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| Important in proving mmicrobes arise from other microbes |
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| Francesco Redi |
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| Italian priest that showed maggots did not spontaneously appear on decaying meat Showed that maggots only appeared when meat was exposed to flies |
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| Lazzaro Spallanzani |
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| Italian priest who disproved spontaneous generation of microbes Sealed flask of sterilized meat did not produce microbes Critics argued that his experiment did not contain air, so results weren't valid |
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| Louis Pasteur |
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| Took Spallanzani's results one step further: Boiled broth then placed in swan necked flask Flasks allowed air in, but no microbes |
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| John Tyndall |
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| When he did Pasteur's experiment, he sometimes had growth Discovered that some organic matter can contain heat-resistant spores |
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| Germ Theory of Disease |
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| Pasteur proposed that the transmission of microbes cause disease Robert Koch proposed 4 criteria that must be met in order to determine if a microbe causes a disease |
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| Koch's Postulate |
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| 1.Microbe always present in diseased organism, absent in healthy 2.Microbe isolated from diseased organism and grown in pure culture 3.Microbe isolated must cause disease in healthy organism 4.Re-isolate same microbe from the now-sick individual |
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| Exceptions to Koch's Postulates |
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| Certain bacteria cause certain diseases Viruses mutate Viruses have to have host Some bacteria can't be cultured in pure form Some microbes elicit symptoms Some microbes can cause different diseases |
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| Application of Koch's Posulates |
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| Barry Marshall- Hilicobacter pylori causative agent of stomach ulcers |
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| John LIster |
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| Listerine, aniseptic surgery |
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| Ignaz Semmeiweis |
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| Hand washing in hospitals |
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| Alexander Fleming |
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| Penicillin (found by accident) |
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| Edward Jenner |
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| Smallpox vaccine |
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| Microbial Classification |
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| Can classify by biochemical properties Woese's three domains of life- based on 16s rRNA, archae are not bacteria, but both prokaryotes |
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| Endosymbiont Theory |
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| Mitochondria were bacteria Chloroplasts were cyanobacteria Bacteria internalized into larger cells and lived together (endosymbiosis) |
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| Tools used in microbiology |
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| Media, Incubator, Winogradsky column, Centrifuges, Molecular techniques, Microscopy |
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| Media |
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| Food or sample for growing microorganisms Pure culture isolation Beginning solid media had gelatin Later used agar (polymer of galactose) |
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| Incubator |
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| Oven used to grow bacteria Different bacteria grow at different temperatures Aerobic- require O2 Anaerobic- require no O2 |
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| Autoclave |
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| Uses high pressure- 15psi And Steam- 121 C to sterilize material |
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| Winogradsky column |
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| Most microbes can't grow on typical medium Used to culture diverse bacterial populations Mud mixed with shredded newspaper (carbon source) Gradients depict different bacterial populations |
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| Molecular Techniques |
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| DNA sequencing Restriction Enzymes PCR Recombinant DNA Closing |
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| Microscopy |
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| Must be used to identify and characterize individual microbes Typical bacteria is 1-3 micrometers |
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| Lenses |
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| Light bends as it passes from one medium to another Refractive index is a measurement of how much light slows down as it passe through a medium The directin and magnitude of the bend depends on the refractive indices of the two medium (i.e. air and glass) |
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| Microscope lenses |
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| The shorter the focal length the more magnification |
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| Microscope Resolution |
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| ability of a lens to separate or distinguish small objects that are close together The shorter the wavelength, the greater the resolution Wider lens closer to specimen can increase resolution Also immersion oil can increase resolution |
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| Types of microscopes: |
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| Bright-field microscop Dark-field microscope Phase contrast Flourescent Electron |
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| Bright-Field Microscope |
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| produces a dark image against a brighter background Typically has 3 to 5 objective lenses We use this type in the lab |
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| The Dark-Field Microscope |
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| Image is formed by light reflected or refracted by specimen Produces a bright image of the object against a dark background Used to observe living, unstained preparations |
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| Phase-Contrast Microscope |
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| Enhances the contrast between intracellular structures having slight differences in refractive index Excellent for observing living cells |
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| Fluorescent Microscope |
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| Concept differs from previous microscopes in that the image is seen because of flourescent light emitted from the object Expose specimen to UV light and forms image resulting from flourescent light Specimens usually stained with flourochromes |
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| Electron Microscope |
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| Electrons behave like wave lengths Allows great resolution Sample must absorb electrons--coat with heavy metal (lenses are magnetic fields) Transmission and Scanning |
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| Transmission Electron Microscop (TEM) |
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| Sample is fixed in chemical Sliced into thin sections Stained with metal Very High Resolutions Good for looking at internal structures |
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| Scanning electron microscopes (SEM) |
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| SAmple is coated with metal Used to observe external structure and morphology |
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| Specimen Preparation |
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| Most specimens must be fixed onto slide and stained in order to be examined Heat fixation- preserves morphology but not internal structures Chemical fixation - used with larger, more delicate organisms Chemical penetrates cell to preserve internal structure |
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| Dyes |
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| Dyes are used to observe cells Dyes have two common features Have chromophore group Able to bind to cells |
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| Simple stain |
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| Uses 1 dye to stain cells Used to determine cell size, shape, and arrangement |
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| Differential Stain |
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| Divides bacteria based on different staining properties Gram staining separates into two groups- gram positive and gram negative |
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| Bacterial Morphology |
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| Cocci- sphere shape Bacilli - rod shape |
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| Cocci |
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| Bunches- staphylococci Chains- Streptococci Groups of 2- diplococci Groups of 4- tetrad |
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| Bacilli |
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| Single- bacillus Chains- Streptobacilli Groups of 2- Diplobacilli Clusters- Coccobacilli |
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| Shapes |
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| Vibrios = bent shape Spiral Irregular |
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| Common Traits of Bacteria |
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| RNA Polymerase Ribosomes Cell wall containing peptidoglycam |
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| Undiscovered Bacteria |
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| Many species uncharacterized Many bacteria cannot yet be grown Unclassified Organisms- identified solely through rRNA sequence |
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| Deep-branching thermophiles |
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| Diverged early from eukaryotes Grown at very high temperatures Aquifex and Thermotoga - live in near-boiling water Deinococcus-Thermus -- Lives at lower temperatures Extremely radiation resistant Very rapid DNA repair |
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| Cyanobacteria |
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| Only bacteria that produce oxygen gas Many fix nitrogen Subcellular structures - thylakoids are the site of photosynthesis, similar to chloroplasts Gas Vessels- used for motility Many form akinetes - specialized spore cells that survive long periods of dessication and germinate when conditions improve |
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| Gram-Positive Firmicutes |
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| Rods and cocci No outer membrane but thick cell wall Many are pathogens (disease-causing) |
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| Gram-positive endospores |
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| Extremely heat-resistant for millennia Toxin-formers (botox, tetanus, gangrene Spore forms inside mother cell |
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| Gram-positive actinobacteria |
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| Acid-fast cell walls Waxy lipids in cell walls |
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| Proteobacteria (gram-negative) |
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| Largest group - 5 major classes |
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| Alpha Proteobacteria |
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| Photoheterotrophs Endosymbionts CAuse rocky mountain spotted fever |
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| Beta Proteobacteria |
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| Lithotrophs - nitrate, sulfur, and iron oxidizers Pathogenic |
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| Gamma Proteobacteria |
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| Lithotrophs- some are phototrophs |
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| Enteric Gamma Proteobacteria |
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| Facultatively anaerobic rods Many are motile Many form biofilms Pathogens |
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| Delta Proteobacteria |
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| Some forms attack other bacteria in "packs" - social movement |
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| Epsilon Proteobacteria |
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| Smallest group of proteobacteria Helicoptor Pylori- cause of stomach ulcers |
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| Nitrospirae |
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| Spiral shape Most oxidize nitrite to nitrate |
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| Bacteroidetes/Chlorobi Group |
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| Obligate Anaerobes- grow only in absence of oxygen Bacteroids- Major flora of human colon, break down toxins in food, provide food Chlorobi- Green sulfur bacteri |
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| Spirochetes |
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| Flexible, narrow spiral shape Flagella at ends |
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| Chlamydiae |
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| Obligate Intracellular parasites Larger reticulate body Grows within cells, cannot survive outside host Small elementary bodies transfer to new host and can survive outside host, similar in function to spore |
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| Planctomycetes |
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| Multiple internal membranes Double membrane surrounds nucleoid |
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| Verrucomicrobia |
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| Irregular shape Contains tubulin |
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| Bacterial cell structure and division |
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| Cytoplasm contains compact genome and ribosomes Cytoplasm is surrounded by cell envelope- includes cell membrane, cell wall (peptidoglycan) and outer membrane |
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| Gram-positive cell wall |
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| Thick cell wall Thin periplasm Plasma membrane |
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| Gram-negative cell wall |
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| Outer Membrane Thin cell wall thick periplasm plasma membrane |
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| Cell Membrane |
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| Made of phospholipid bilayer Proteins embedded in membrane- integral and peripheral proteins, transport materis into and out of cell, senses the outside world, anchor membrane to envelope |
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| Transport |
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| Protons pushed out cell by pumps Generates proton motive force PMF is used to generate ATP- ATP synthase uses PMF for energy |
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| Transporters |
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| move material into or out of the cell passive transport follows concentration gradient of material Passive diffusion lets small molecules into cell |
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| Periplasm |
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| Not empty space Contains protein oligosaccharide, salts, and the peptidoglycan |
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| Peptidoglycan layer |
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| Provides strength and rigidity to cell Sugar chains wrapped in circles around cell Sugar chains linked to each other by short polymers of amino acids or peptides |
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| Outer Membrane |
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| Composed of phospholipid, Lipopolysaccharid (LPS) and protein LPS is an endotoxin- elicits immune response |
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| Bacterial Nucleoid |
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| Single loop of stranded DNA Single molecule of DNA Attached to cell envelope |
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| Gene Expression |
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| RNA Polymerase transcribes DNA to mRNA Ribosome translates RNA to Protein |
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| Cell Division |
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| Cell elongates as it grows (adds new cell wall at equator) DNA replicates to make 2 chromosomes Cell undergoes septation Binary Division |
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| Photosynthesis |
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| Cyanobacteria have thylakoids Carboxysomes fix carbon and use energy to make sugar |
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| Inclusion bodies- Intracellular deposits of material |
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| Glycogen- sugar for energy PHB (fatty acid polymer) for energy Polyphosphate to store material Sulfur for disposal |
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| Cell Attachment |
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| Fimbriae and pili attach cells to surfaces Secretion systems attach cells to prey Essential for bacterial pathogemicity |
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| Cell Motility |
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| Flagella- long, helical protein filaments attached at ends and over whole cell Flagella rotate to propel cell |
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| Chemotaxis |
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| Movement away or towards a chemical Chemoattractors cause flagella to rotate counter-clockwise pushing bacteria forward (run) Chemorepellents cause flagella to rotate (or tumble) clockwise, pushing bacteria away |
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| Microbial Growth |
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| Microbial nutrition All life requires: Electron flow to drive processes Energy to move electrons Materials to make cells |
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| Electron Flow Requires |
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| Source of electrons Electron Acceptor Source of energy |
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| Facilitated Transport |
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| Transport proteins are required Substrate moves along centration gradient; no energy is required |
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| Active Transport example |
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| Phosphotransferase system Modifies material as it enters the cell Used to phosphorylate glucose once it enters the cell |
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| Nutrient Types |
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| Micronutrients- small amounts of nutrients required Macronutrients- large amounts of nutrients needed Nutrients required by bacteria differ between species |
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| Ways to obtain pure culture |
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| Streak Plate- streak cells on plate, agar inhibits spread of microbes on plate, all cells in colony derive from single cell Dilution of culture in broth- reduces number of cells in each tube, spread liquid on plate to see single colonies |
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| Ways to monitor Growth |
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| Agar plate Counting Chamber Spectrophotometer |
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| Growth cycle of bacteria |
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| Lag Phase- cells synthesizing materials, not dividing Log phase= exponential growth Stationary Phase Death Phase |
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| Biofilms |
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| Cells secrete material to hold to a surface Cells acting together, cells signal to each other, protects against dispersion, prevents antibiotics from infiltrating |
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| Cell Differentiation |
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| Cells respond to changing environment Endospores- protect against bad conditions, forms inside mother cell |
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| Variations in the environment can impact growth |
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| pH Temperature Osmlarity Oxygen Content Pressure |
