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220 Cards in this Set
- Front
- Back
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Antony von Leeuwenhoek
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1st person to observe & describe microorganism accurately (bacteria & protozoa)
made simple lenses (50-300x) |
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Robert Hooke
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1st person to publish the depiction of a microorganism (fruiting structure of molds "Hairy Mould" colony)
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Francesco Redi
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proved biogenesis of large organisms
generation of maggots |
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Luis Pasteur
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proved biogenesis of microorganisms through "swan-neck" flasks
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Robert Koch & his postulates
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1. suspected pathogenic organism should be present in all cases of the disease & absent from healthy animals
2. suspected organism should be grown in pure culture (only one) 3. inject pure culture-> healthy host experimental animals develop same signs & symptoms 4. organism should be re-isolated & shown to be same as original Established relationship between Bacillus anthracis & anthrax Developed pure culture methods (grown on solid media, isolation of pure culture) |
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Basic Properties of Cells
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1. Metabolism
2. Reproduction (growth) 3. Differentiation 4. Communication 5. Movement 6. Evolution |
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Prokaryotes
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single cells
lack nucleus 70S ribosomes 1-10 micrometer 5x10^3 cells on earth |
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Bacteria
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simple shapes: round, rod, spiral
cell walls: peptidoglycan |
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Archaea
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cell wall: more complex
found in extreme environments: high T, P, salt |
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Eukaryotes
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single-celled or multicellular
have true nucleus 80S ribosome 10-100 micrometers |
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Protozoa
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single-celled
no cell walls motile aquatic environments part of food chain some are pathogens |
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Algae
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single-celled or multicellular
have cell walls photosynthetic in soils, lakes, oceans some produce toxins |
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Fungi
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single-celled or multicellular
have cell walls no photosynthetic pigments nature's "recyclers" some are pathogens |
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Virus
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acellular
made of nucleic acid & protein obligate intracellular parasites |
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Carl Woese
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used rRNA sequencing to compare organisms
led to discovery of Archaea |
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Monomorphic
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single shape
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Pleomorphic
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variable shape
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Hopanoid
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embedded membrane protein
sterol-like stabilize membrane |
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Mesosome
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invaginations of plasma membrane
-cell wall formation in cell division -chromosome replication & distribution -secretory processes artifacts of chemical fixation process |
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Internal Membrane System
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mesosomes
complex infoldings in photosynthetic bacteria & prokaryotes with high respiratory activity -aggregates of spherical vesicles, flattened vesicles, tubular membranes |
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Inclusion Bodies
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Made of organic or inorganic
Nutrient & energy storage |
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Poly-B-hydroxybutyrate
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Inclusion body for phosphate storage (Biodegradable plastics)
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Magnetosome
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Inclusion body, iron containing orientation in magnetic field
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Nucleoid
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irregularly shaped region
single circle of double-stranded DNA |
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Plasmid
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extra-chromosomal DNA
Small, circular, mini-chromosomes Extra genetic info not required for cell growth & may provide selective advantage Transfer between bacteria via conjugation |
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Gram Staining
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1. smear Crystal Violet for 1 min (all purple)
2. iodine solution for 3 min (all purple) 3. decolorize with alcohol ~20 sec (G+ purple, G- colorless) 4. counterstain with safranin 1-2 min (G+ purple, G- pink) |
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Capsule
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thick, structured difficult to wash
made of polysaccharide &/or protein adherence, resistance to desiccation, resistance to phagocytosis, improve motility |
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Slime Layer
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thin, slimy, easy to wash off
made of polysaccharide &/or protein adherence, resistance to desiccation, resistance to phagocytosis, improve motility |
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Fimbrae
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only in G-
used for attachment (adhesion protein)-> invasion nutrient uptake not for motility short, hair-like structures |
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Pili
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type of fimbrae for DNA transfer
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Pattern of Bacterial Movement
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"Runs" CCW rotation of flagella filament
"Stop/Tumbles" CW |
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Endospores
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"resting/dormant state" structure within bacterial cell
DNA & proteins survival of adverse conditions can "reactivate" in favorable environment i.e. Bacillus, Clostridium types: central, terminal, subterminal |
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Sporulation
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spore formed under stress
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Stages in Spore Transformation
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Reactivation
-prepare spores for germination Germination (Spore into vegetative) -spore swelling -rupture of absorption of spore coat -loss of resistance -increased metabolic activity Outgrowth -emergence of vegetative cell |
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Requirements for Microbial Growth
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Temperature
pH Osmotic pressure Oxygen concentration Macroelements Trace elements Organic growth factors |
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Low Temperature Growth Microbes
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Membranes with high levels of unsaturated fatty acids; semifluid
Psychrophiles -growth at 0-20C (<15) -polar habitats Psychotrophs (facultative) -growth at 0-7C (20-30C) -food spoilage |
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Stalk
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Caulobacter
Plasma membrane Nutrient absorption & surface attachment |
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Hypha
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Streptomyces
Plasma membrane, ribosomes, DNA Increase metabolism |
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High Temperature Growth Microbes
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Protein Structure - more H bonds, prolines & chaperones
DNA - histone-like proteins Membrane - more saturated, branched, high MW lipids & ether linkages Thermophiles -prefer 55-65C or higher -hot water lines, compost piles Hyperthermophiles -prefer 80-100C -geothermal areas of ocean floor Streptomyces thermoautotrophicus |
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Moderate Temperature Growth Microbes
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Mesophiles
-prefer 20-45C -human pathogens |
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pH preference Microbes
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Neutrophile (5.5-8)
Acidophile (<5.5) Alkalophile (>8.5) internal pH near neutrality through proton/ion exchange acid-shock proteins (chaperones) change pH by: -acidic/basic waste products most media have buffers to prevent growth inhibition |
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Osmotic Pressure Preference MIcrobes
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Isotonic
Hypotonic (lower solute outside cell) = osmotic lysis Hypertonic (higher solute out) = plasmolysis Osmotolerant (high solute out) i.e. Staphylococcus aureus (3M salt on skin) Extreme halophiles (intra K/Na high) in marine environments like Great Salt Lake, Utah |
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Oxygen Requirement Microbes
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Obligate aerobe (requires O2)
Facultative anaerobe (prefers O2) Microaerophile (requires O2 in reduced concentrations 2-10%) Aerotolerant anaerobe (doesn't require but unharmed by O2) Obligate anaerobe (can't use/detoxify O2 & killed by it) |
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Macroelements
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Carbon (heterotroph/autotroph)
Oxygen, Hydrogen (carbs, lipids, proteins, nucleic acids, organic compounds, H2O) Nitrogen (AAs, nucleotides, carbs, lipids from protein, ammonium, nitrate, nitrite; N2 fixation from atmosphere) Sulfur Phosphorus |
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Organic Growth Factors
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Amino Acids (protein synthesis)
Purines & Pyrimidines (nucleic acid synthesis) Vitamins (enzyme cofactors) -cell can't synthesize this because of lack of synthetic enzymes, so supplied by environment |
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Passive Diffusion
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doesn't require energy
dependent on size of gradient H2O, O2, CO2, small uncharged molecules move large molecules, ions, polar substances aren't able to move |
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Facilitated Diffusion
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not energy dependent
from high to low concentration size of concentration gradient impacts rate of uptake facilitated by permeases transports glycerol, sugars, & AAs more in eukaryotic cells conformational change of carrier after binding an external molecule-> release of molecule on cell interior |
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Binary fission
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process of cell division in bacteria
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Measurement of Bacterial Growth
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Direct Counts with Calibrated Slide Chamber
-easy, inexpensive, quick -eukaryotes & prokaryotes -can't distinguish living from dead Plate Count Methods -Spread Plate -Membrane Filtration Indirect/Turbidity -more cells in test tube-> more cell mass-> more light scattered-> less light detected |
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Total Cell Count
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turbidity/microscope count
doesn't distinguish living from dead |
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Viable Cell Count
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plate count or membrane filtration
only live cells grow |
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Culture Media
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Chemically defined media (precise composition known)
Complex media (unknown) Contains: Peptones (protein hydrolysates prepared by partial digestion of protein) Extracts (aqueous, beef/yeast) Agar (Sulfated polysaccharide used to solidify liquid media) |
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Selective Media
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inhibit certain microbes
"Brilliant green agar" G+ bacteria inhibits |
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Differential Media
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"Blood agar" hemolysis
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Selective & Differential Media
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"MacConkey agar"
inhibits G+ & detects lactose fermentation |
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Enrichment Media
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isolation of specific organisms
nitrogen fixing bacteria isolate in media without nitrogen (Siderophore in Azobacter Vinelandii) |
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Sterilization
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all life forms (bacterial endospores & viruses) are either destroyed/removed from object/habitat
chemicals, heat, radiation |
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Disinfection
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killing, inhibition, removal of microorganisms that may cause disease on inanimate objects
-may not kill endospores ethanol, cationic detergents |
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Sanitization
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microbes reduced to levels "considered safe by public health standards"
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Antisepsis
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reduction of total microbial population on living tissue (prevention)
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Germicide
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kills microbes
-not endospores |
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Bacteriostasis
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stops bacterial growth
must be continually present |
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D value/ Decimal Reduction Time
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time required to kill 90% at specific temperature
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Factors affecting Antimicrobials
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1. Population size
2. Population Composition -tough to kill bacterial endospores & Mycobacterium tuberculosis but easy to kill "vegetative" growing cells 3. Duration of exposure 4. Concentration 5. Temperature (higher, enhances antimicrobial activity) 6. Local environment -pH, viscosity, organic matter (inhibits chemical agents) -cause leakage on membrane-> proteins denature/inhibit-> nucleic acids damage/break |
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Methods of Microbial Growth Control
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Physical control methods
-Heat -Low Temperature -Radiation -Filtration Chemical Control Methods -Alcohols -Aldehydes -Detergents |
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Heat as Method of Microbial Growth Control
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(+) widely-used methods, inexpensive & easy to apply
(-) may not sterilize, some damaged by heat Dry Heat -Hot oven (170C for 2 hours) for glassware, glass pipettes -Direct flaming for bunsen (loops) & incineration of trash & contaminents Moist Heat -Boiling (10 min-vegetative) sanitize but don't kill spores -Autoclave (saturated steam under pressure) for endospores, media, and surgical instruments -Pasteurization for brief 60C like wine |
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Thermal Death Time
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minimum time needed to kill organisms in suspension of specific temperature
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Z value
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increase in temperature required to reduce D to 1/10
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Filtration
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heat-sensitive agents
antibiotics, vitamins, AAs filter air using surgical masks, cotton plugs on culture vessels, high-efficiency particulate air filters (HEPA) for laminar flow biological safety cabinets |
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Low Temperature for Microbial Growth Control
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Refrigeration (4C) or Freezing (-20C)
stops production due to lack of liquid water some killed by ice crystal disruption of cell membranes bacteriostatic |
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Radiation for Microbial Growth Control
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Non-iodizing radiation
-UV light wavelength 260nm -"germicidal lamps" damages DNA & kills germs -surface sterilization (-)poor penetration of glass, water Ionizing radiation -X-rays, gamma rays -kill spores -for lab & medical supplies -generates electrons, OH, H but disrupts DNA & protein i.e. Clostridium botulinum & Deinococcus radiodurnas (500x resistant) |
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Desiccation
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drying-bacteriostatic
freeze-dried foods |
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Osmotic Pressure
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High concentration of sugars/salts
Food preservation like jams & salted meats |
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Ideal Chemical Agent
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active against wide range of microbes
non-corrosive & nontoxic soluble in water, long shelf-life non-staining, pleasant odor cost-effective |
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Phenol & Derivatives
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denature protein & disrupt membrane
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Alcohol
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Ethanol, Isopropanol
denatures proteins & dissolves lipids doesn't kill spores |
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Halogens
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Iodine
antiseptic/oxidize cell constituents & iodinates proteins |
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Heavy Metals
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Cu
algicide in water but toxic |
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Detergents
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Quaternary ammonium compounds
cleaning & sanitization in hospitals & labs doesn't kill G- |
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Aldehydes
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Formaldehyde
sterilize surgical instruments combine with & inactivate nucleic acid & proteins but allergical reaction |
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Sterilizing Gases
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Ethylene oxide
sterilization of heat-sensitive medical equipment kills bacteria, mold & fungi |
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Evaluation of Chemical Control Methods
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use-dilution tests: rate at which selected bacteria are destroyed 95%
i.e. Staphylococcus, Salmonella, Pseudomonas Phenol Coefficient: dilutions of test agent compared to dilution of phenol |
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Mn
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SOD, oxygen-evolving complex of photosystem II
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Zn
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SOD, alcohol dehydrogenase
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Cu
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SOD, cytochrome oxidase
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Co
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Vitamin B12, nitrile hydratase
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Mo
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Nitrogenase, nitrate reductase
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Ni
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CO Dehydrogenase, Hydrogenase
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Major Nutritional Types of Microorganisms
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1. Carbon (Heterotroph/Autotroph-CO2)
2. Energy (Chemotroph: organic-glucose, inorganic-H2S; Phototroph) 3. Electron (Organotroph-glucose; Lithotroph-Fe2+, H2) |
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Chemoorganotrophic heterotrophy
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most bacteria, fungi, protozoa, most pathogenic microbes
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Photolithotrophic Autotrophy
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Cyanobacteria, Algae
capable of "oxygenic photosynthesis" |
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Chemolithotrophic Autotrophy
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nitrifying bacteria, iron-oxidizing bacteria, sulfur-oxidizing bacteria
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Photoorganotrophic Heterotrophy
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purple & green nonsulfur bacteria
capable of "anoxygenic photosynthesis" in lakes, streams, soil |
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Glucose Catabolism Pathways & Endproducts
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Glycolysis//Pyruvate
Pentose phosphate//3-7Carbon sugars Entner-Doudoroff//Pyruvate |
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Substrate-level Phosphorylation
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synthesis of ATP from ADP by phosphorylation coupled with exergonic breakdown of a high energy organic substrate molecule
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Summary of Glycolysis
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Glucose + 2ADP + 2Pi + 2NAD -> 2 pyruvate + 2ATP + 2NADH + 2H
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Fermentation
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In absence of aerobic/anaerobic respiration
Regenerates NAD, oxidizes NADH to NAD if NAD not regenerated, glycolysis stops uses organic molecules as electron acceptor (endogenous, usually pyruvate or derivative) forms alcohols/organic acids homolactic fermenters- yogurt, sauerkraut, pickles alcoholic fermentation- alcoholic beverages, bread |
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ATP yield from Aerobic oxidation of glucose by eukaryotic cells
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Glycolytic Pathway: substrate-level phosphorylation (2 ATP)
oxidative phosphorylation with 2NADH (6 ATP) 2 Pyruvate to 2 Acetyl-coA: oxidative phosphorylation with 2 NADH (6 ATP) TAC: substrate-level phosphorylation (GTP) (2 ATP) oxidative phosphorylation with 6 NADH (18 ATP) oxidative phosphorylation with 2 FADH2 (4 ATP) TOTAL: 38 ATP |
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Pasteur Effect
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facultative microbes have both fermentation & aerobic respiration
with O2, consumes less glucose without O2, consumes more glucose |
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Biosynthesis
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Turnover-> continual degradation & re-synthesis of cellular constituents
1. Macromolecules synthesized from limited number of monomers->saves genetic storage capacity, biosynthetic raw material & Energy 2. Many enzymes used for both catabolism & anabolism-> saves material & Energy 3. Catabolic & anabolic pathways not identical despite shared enzymes-> permits independent regulation |
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Synthesis of Sugars & Polysaccharides by Heterotrophs
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Gluconeogenesis- synthesize glucose & fructose from noncarbohydrate precursors
most other sugars made from them functional reversal of glycolysis 7 enzymes shared 4 enzymes unique to gluconeogenesis |
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Level of Organization of Molecules to Cells
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Inorganic molecules (CO2, NH3, H20, PO4)
Monomers (Nucleotides, AAs, sugars, fatty acids) Macromolecules (Nucleic acids, proteins, polysaccharides, lipids) Supramolecular systems (membranes, enzyme complexes) Organelles (Nuclei, mitochondria, ribosomes, flagella) Cells (Bacteria, algae, fungi, protozoa) |
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Catabolism of Chemoorganotrophic Heterotrophy
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1. Larger nutrients broken down
Polymers-> Monomers Proteins-> AAs Carbs-> Simple Sugars Lipids-> Fatty acids & glycerol (no energy release) 2. Monomer units-> acetyl coA synthesis of ATP, NADH &/or FADH2 3. complete oxidation of molecules to CO2, ATP, NADH & FADH2 TCA cycle electron transport/oxidative phosphorylation |
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Conversion of pyruvate to acetylaldehyde
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Pyruvate Decarboxylase
Pyruvate-> Acetylaldehyde + CO2 ethanol producing yeast & bacteria |
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Lactic Acid Fermentation
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Lactate Dehydrogenase
Pyruvate-> Lactate (NADH->NAD) homolactic fermentation Lactic acid bacteria yogurt & in tooth decay |
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Formic acid fermentation
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useful in identification in members of Enterobacteria
1. Mixed acid fermentation forms formic acid (CO2 + H2), ethanol, acetic acid, lactic acid, suscinic acid (E.coli) 2. 2,3 Butanediol fermentation forms 2,3 butanediol, ethanol (Enterobacter) |
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Methyl Red Test
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Voges-Proskauer Test
use fermentation endproducts to identify bacteria measures acidity of fermentation endproducts mixed acid-> acidic 2,3 butanediol-> neutral positive methyl red-> acid-> red negative methyl red-> neutral-> yellow |
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Strickland Reaction
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1AA oxidized
2nd AA= electron acceptor i.e. Clostridium (anaerobe prefer high-protein environment) oxidizes alanine; produces NADH + ATP reduces glycine; regenerates NAD |
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Tricarboxylic Acid Cycle (Citric Acid Cycle, Kreb's Cycle)
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completes oxidation & degradation of glucose & others into CO2
produces ATP via substrate phosphorylation produces reduced coenzymes (NADH, FADH) common in aerobic bacteria, free-living protozoa, most algae & fungi amphibolic provides carbon skeletons for biosynthesis catabolic: acetyl coA from lipids & proteins anabolic: TCA intermediates for synthesis 3 stages based on size of intermediates (6, 5, 4) which are separated by 2 decarboxylation reactions (2 CO2) 3 NADH & 1 GTP produced by substrate-level phosphorylation 1 FADH2 generated by 1 acetyl-coA & substrate-level phosphorylation |
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Electron Transport & Oxidative Phosphorylation
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only 4 ATP synthesized directly from oxidation of glucose to CO2
most ATP made when NADH & FADH2 oxidized in electron transport chain -electron carriers operate together to transfer electrons from NADH & FADH2 to terminal electron acceptor -electron flow from carriers with more negative E0 to positive -in mitochondria (euk) plasma membrane (pro) |
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Electron Transport Chain in Eukaryotes
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4 complexes of carriers (transport electron to O2)
coenzyme Q & cytochrome C connect complexes pro- branched, different cytochromes, utilize electron acceptors (nitrate) ATP synthesized by protons pumped across membrane -proton motive force (gradient of protons & membrane potential due to unequal distribution of charge) -ATP synthase (protons into mitochondrial matrix) released energy to make ATP by oxidative phosphorylation (3 ATP per NADH, 2ATP per FADH2) |
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Chemolithotrophs
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Hydrogen oxidizing bacteria (H2->2H+2e; Ni/Fe Hydrogenase)
-alcaligenes, Streptomyces thermoautotrophicus -roistonia eutropha: 2 Hydrogenases Nitrifying bacteria: oxidize ammonia to nitrite/nitrate (nitrification) -NH4+1 1/2 O2-> NO2+H2O+2H nitrosomonas -NO2+1/2 O2-> NO3 nitrobacter -nitrite oxidoreductase -Ammonia-oxidizing bacteria: Hydrosylamine oxidoreductase, ammonia, monoxygenase CO oxidizing bacteria (CO->CO2) -Aerobic (Mo in active site of CO-Dehydrogenase, MOlybdopterin) i.e. Streptomyces thermoautotrophicus, Oligotropha carboxidovorans -Anaerobic (Ni in active site of CO-Dehydrogenase) i.e. Carboxydothermus hydrogenoformans Iron Oxidation by Acidithiobacillus ferroxidans |
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Carbon Assimilation (Carbon fixation)
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CO2 incorporated via Calvin-Benson cycle
energy source- light (photoautotroph)/inorganic chemicals (chemolithotroph) product: organic carbon needed by heterotrophs |
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Nitrogen Fixation
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enzyme: nitrogenase
very high Energy requirement N2 + 8H + 8e + 16 ATP -> 2NH3 + H2 + 16ADP + 16Pi widespread among microorganisms -Rhizobium - symbiont with legumes -many free-living bacteria (Azotobacter) -Cyanobacteria nitrogenase reaction is anaerobic inhibited by O2 |
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Anaplerotic Reactions
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replenish TCA cycle intermediates -> allow TCA to function during periods of active biosynthesis
1. Anaplerotic CO2 fixation 2. Glyoxylate Cycle |
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Peptidogylcan Synthesis
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1. sugars synthesized in cytoplasm linked to carrier uridine diphosphate
2. UDP-NAM (N-acetyl muramic acid) linked to AA (no ribosomes/tRNA required, ATP needed) 3. NAM-peptide from UDP to bactoprenol phosphate 4. NAG (N-acetyl glucosamine) from UDP to NAM-peptide-> forms peptidoglycan repeat unit 5. peptidoglycan repeat unit transported across membrane by bactoprenol 6. peptidoglycan unit added onto growing peptidoglycan chain 7. bactoprenol carrier returns to inside of membrane 8. transpeptidation-crosslinks formed in peptidoglycan Inhibited by some antibiotics->weak cell wall, bacteria lysis penicillin inhibits transpeptidation |
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Measurement of Virulence
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ID50 - infectious dose for 50% of population
LD50 - lethal dose for 50% |
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Pathogenesis of Bacterial Disease
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process of disease causation
1. Attachment of microbe 2. Invasion through host 3. Evasion of host defenses 4. Mechanisms of damage to host tissues |
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Contact & Entry into Host
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source of organism: disease reservoirs
modes of transmission: contact, vehicles (food/H2O), vectors portals of entry: respiratory, gastrointestinal, urogenital, skin attachment- adherence structure (fimbrae, capsules, adhesins) |
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Invasion & Growth in Host
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passive invasion (cuts, scratches, insect, phagocyte engulfs)
active invasion (production of lytic enzymes, attack on cell surface) growth in or on host cells (host may supply heme groups/ATP) |
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Evasion of Host Defenses
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survival of bacteria
evasion of complement system: G-bacteria-lengthen "O" chains on LPS resistance to phagocytosis: capsules (Streptococcus pneumoniae, Neisseria Haemophilus) |
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Damage to Host Tissues
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Direct cell damage via host cell invasion & lysis
Toxin-mediated damage -endotoxin (G-) produced as bacteria divide or die -exotoxin (G+ & some G-) produced by living bacteria |
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Exotoxin
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source: G+ & some G- living bacteria
chemistry: protein effect on host: specific heat stability: unstable at 60-80C toxicity: highly in small amounts immunology: can vaccinate fever: usually none genetics: reside on plasmid disease: tetanus, botulism, diphtheria |
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Endotoxin
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source: G- bacteria dying
chemistry: Lipid A portion of LPS effect on host: fever, weakness, inflammation heat stability: heat-stable toxicity: moderate (high lethal) immunology: no vaccines fever: induces via IL-1 release genetics: encoded by chromosomal genes disease: Meningocococal meningitis, typhoid fever, G- |
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Neurotoxins
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Block or activate specific neurons
May be ingested pre-formed -Clostridium botulinum (Botox blocks nt release-> "flaccid paralysis") May be formed in body -Clostridium tetani |
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Membrane-Disrupting Toxins
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Phospholipases (exotoxin)
-Clostridium perfringins alpha toxin (unstable host cell membrane) |
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Endotoxin in Bacterial Diseases
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indirect effects on host
LPS enters monocytes & macrophages Host cells release cytokines-> fever |
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Vaccines
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Active immunization
-vaccine administered & induces protective immunity Passive immunization -artificially acquired -can be produced by injecting preformed antibodies Whole-Organism Vaccines -inactivated/attenuated Purified macromolecule vaccines -capsules, toxoids, surface antigens Recombinant vector vaccines -attenuated recombinant nonpathogenic microorganism -genes encode antigen from pathogen DNA vaccines (not approved yet) |
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Therapeutic index
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ratio toxic dose to therapeutic dose
higher ratio, more effective agent |
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Categories of Effectiveness
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Narrow spectrum drugs
-affects one or a few types of microbes -Penicillin G kills G+ Broad Spectrum drugs -affects many types of microbes -Tetracycline kills G+, G-, intracellular bacteria |
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Categories of Antimicrobial Agents
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"Natural" synthesized by microbes
-Fungi-Penicillum; Cephalosporium Semi-synthetic- isolated from microbes, modified in lab Synthetic- directly synthesized in lab |
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Mode of Action of Antimicrobial Agents
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cell wall synthesis
protein synthesis nucleic acid synthesis specific enzymes |
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Cell Wall Synthesis Inhibitors
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Penicillin
-B-lactam antibiotic inhibits transpeptidation step of peptidoglycan synthesis -bacteriocidal Penicillin G ("natural" penicillin) -effective against G+, some G- -must be injected, destroyed by stomach acid |
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Resistance to Penicillin
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some bacteria produce penicillinase (B-lactamase)
penicillin converted to penicilloic acid |
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Protein Synthesis Inhibition
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Tetracycline binds 30S subunit, inhibits aminoacyl tRNA binding
-broad spectrum affects both G+ & G- & intracellular bacteria -bacteriostatic Aminoglycosides: Streptomycin -binds 30S subunit; cause misreading of mRNA -bactericidal -toxic side effects: deafness & allergic response Macrolide : Erythromycin -bind 50S subunit -broad spectrum -bacteriostatic |
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Inhibition of Nucleic Acid Synthesis
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Quinolines: Nalidixic acid
Fluoroquinolones: Ciprofloxacin -inhibit DNA gyrase; inhibits DNA replication -broad-spectrum |
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Inhibition of Specific Enzymes
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Sulfonamide inhibits folic acid synthesis; inhibits purine & pyrimidine synthesis
-competes with -aminobenzoic acid during folic acid synthesis (decline of folic acid in cell, inhibits DNA/RNA synthesis) |
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Botulism
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causative agent: Clostridium botulinum
mode of transmission: ingestion of toxin in food signs/symptoms: flaccid paralysis, death due to respiratory/cardiac failure virulence factors: neurotoxin-blocks nerve transmission treatment: antisera prevention: improved food preservation foods |
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Staphylococcal "Food Poisoning"
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causative agent: Staphylococcus aureus
source: person preparing food foods: ham, cream pies, puddings, any foods cooked & left at R.T. incubation hour: 1-8 hours signs & symptoms: nausea, vomit, abdominal cramps, diarrhea treatment: oral or IV rehydration, recovery in 24-48 hours prevention: handwashing by food preparer & refrigeration of foods |
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Helicobacter Peptic Ulcer Disease
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causative agent: Helicobacter pylori
signs & symptoms: erosion & ulceration of stomach lining treatment: antibiotics & pepto-bismol -ammonia that's produced is toxic to epithelial cells of stomach & protease, catalase, phospholipase -damages epithelial cells |
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Diphtheria
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causative agent: Corynebacterium diphtheriae
mode of transmission: airborne & respiratory droplets signs & symptoms: cold-like fever & sore throat; Pseudomembrane in throat virulence factors: exotoxin (encoded by lysogenized phage); toxin inactivates EF-2, blocks protein synthesis treatment: antibiotics & anti-toxin antisera prevention: DPT vaccine |
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Bacterial Pneumonia
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predisposing factors:
-prior viral infection-cold/influenza -exposure to pollution -smoking -poor nutrition, alcoholism, drug use -other health problems- heart & lungs |
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Streptococcal Pneumonia
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causative agents: Streptococcus pneumoniae, G+ coccus; forms capsule
signs & symptoms: fever, chest pain & cough virulence: capsule pneumolysin (damages blood vessels in lungs) treatment: antibiotics vaccine: Streptococcal pneumoniae vaccine; penetration into lower respiratory tract-> Streptococci trapped by mucus & removed by ciliary action -> macrophages phagocytosis-> ciliated epithelium damaged by viruses, toxins, smoke, chemicals-> fluid accumulates-> lowered activity of macrophages-> growth on damaged ciliated epithelium-> growth in fluids & alveoli-> fluid accumulation |
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Anthrax/Woolsorters' Disease
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causative agent: Bacillus anthracis
mode of transmission: cuts in skin (anthrax); inhalation (Woolsorter's disease) signs/symptoms: cutaneous anthrax-skin pustule; pulmonary anthrax-Woolsorter's disease-Pneumonia (100% lethal) treatment: antibiotics (if early) prevention: vaccine |
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Tetanus
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causative agent: Clostridium tetani
mode of transmission: puncture wound signs/symptoms: muscle spasms, "lock-jaw", death from suffocation virulence factors: neurotoxin: tetanospasmin; blocks inhibitory neurons->overactivity muscles treatment: passive immunization with human anti-tetanospasmin immunoglobulin; vaccine booster prevention: DPT vaccine |
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Booster dose
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reexposure to immunizing antigen
higher immunity against antigen back to protective levels after it decreases or after specified time |
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Bubonic Plague
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causative agent: Yersina pestis
mode: vector: rat flea reservoir: squirrels, rats, prairie dogs signs & symptoms:swollen & blackened lymph nodes (buboes), fever |
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Taxis
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arrangement/order
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homos
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Law
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nemein
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to distribute/govern
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classification
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arrangement of organisms into groups/taxa based on similarities/evolutionary relatedness
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nomenclature
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assignment of names to taxonomic groups in agreement with published rules
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How old is the planet?
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4.6 billion years
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When did the first prokaryotic cells occur?
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3.5-3.8 billion years ago
found in stromatolites & sedimentary rocks |
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stromatolites
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layered rocks formed by incorporation of mineral sediments into microbial mats (anaerobic)
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When did oxygen production being and who did it?
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Cyanobacteria (oxygenic phototrophs) 2.5-3 billion years ago
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When did eukaryotes arise?
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from prokaryotes 1.4 billion years ago
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Evolution of eukaryotes
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1. nuclei, mitochondria & chloroplasts arose by invagination of plasma membranes to form double membrane structures containing genetic material & capable of further development & specialization
2. Endosymbiotic hypothesis -fusion of ancient bacteria & archaea -chloroplasts arose from free-living phototrophic bacterium that entered symbiotic relationships with primitive eukaryotes -mitochondria arose similarly |
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Taxonomic Ranks
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Domain
Phylum Class Order Family Genus Species |
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Higher organisms
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groups of interbreeding natural populations reproductively isolated from other groups
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Prokaryotes/species
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asexual collection of strains sharing stable properties
Phenotypically distinguishable Genetically similar -similar GC composition -70% or > DNA sequence similarity -same sequence of core housekeeping genes (genes coding for products that are required by all cells & expressed continually) Population dropped from single organism/pure culture isolate Population distinguishable from at least some other population within particular taxonomic category Strains within species might differ slightly |
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Natural Classification Systems
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according to shared characteristics
most desired since reflects biological nature of organisms 1st used by Linnaeus 1. Phenetic Classification -reveal evolutionary relationships but not dependent on phylogenetic analysis 2. Numerical Taxonomy (multistep process) -phenetic classification systems -code info about properties or organisms (1=has trait, 0=don't)>50 characters -construct similarity matrix -construct dendograms 3. Phylogenetic Classification System -evolutionary relationships -"molecular chronometers"-use of protein/nucleic acid sequence as measure of change over time (16S ribosomal RNA, proteins: histones, cytochrome C) |
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Biovars
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biochemical physiological strain variant
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Morphovar
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morphological variant
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Serovar
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antigenic variant
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Type Str
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usually one of first strains of species studied
often most fully characterized not necessarily most representative member of species |
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Binomial system of nomenclature
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Carl von Linne (Carolus Linnaeus)
-genus name-italicized & capitalized -species name-italicized but not cap -can be abbreviated after first use |
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"Classical Characteristics"
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Morphological: cell shape, size, Gram stain
Metabolic: O2 required, fermentation end products Ecological: T required, habitat Genetic: chromosome exchange via conjugation/transduction |
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"Molecular Characteristics"
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Protein comparison: AA sequence
Nucleic acid base composition: GC content Nucleic acid hybridization Nucleic acid sequencing |
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Comparison of proteins
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AA sequence of proteins with same function
-electrophoretic mobility -determination of immunological cross-reactivity -enzymatic properties |
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Nucleic acid hybridization
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measure of sequence homology
bind nonradioactive DNA to nitrocellulose filter-> incubate filter with radioactive ssDNA-> measure amount of radioactive DNA attached to filter-> retained radioactivity can be used to determine homology Usually comparison of rRNA genes -critical organelle in all microbes -perform same functional role in all ribosomes (structural elements) -structure changes slowly with time (provide stable sequence for comparison) Increasingly, comparison of entire genomes |
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Microbial Chronometers
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Nucleic acids/proteins used as "docks" to measure amount of evolutionary change over time
Assumptions: -sequences gradually change over time -changes are selectively neutral & relatively random -amount of change increases linearly with time Problems: -rate of sequence change can vary over time -different molecules & different parts of molecules can change at different rates |
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Creating phylogenetic trees from molecular data
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1. align sequences
2. determine number of positions that are different 3. express difference-> evolutionary distance 4. use measure of difference to create tree |
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Microbial Genetics
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info about evolutionary & horizontal gene transfer
Future: improved diagnostic methods, new vaccines/disease treatments, better understanding of microbial diversity, discovery of novel enzymes for industrial uses |
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Escherichia coli genomic map & genome
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genome size: 4.6 x 10^6 bp
gene number: 4288 58% no known function 10% energy & metabolic pathways 12-14% transport protein genes 8% replication, transcription, translation Single chromosome Length: 1.4 mm |
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Semiconservative DNA replication
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each synthesized copy contains one new & one old strand
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Bidirectional DNA replication
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two replication forks move around the DNA forming intermediates
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Mutations
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change of single bases, additions or deletions
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Recombination
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whole chromosomes/regions of chromosomes transferred between cells
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Point Mutation
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due to mistakes by DNA polymerase which occurs rarely; corrected by "proofreading"
due to alteration of bases after DNA synthesis caused by chemicals or radiation |
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Silent Mutation
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no effect
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Direct Selection of Mutant
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treat cells with mutagen-> add agent to kill "wildtype"-> only mutants will grow (penicillin-resistance)
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Indirect: Replica Plating
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expose cells to mutagen-> compare growth on complete media (lacking essential components) (lysine)-> rapid screening method
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Ames Test
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uses mutant Salmonella strain (his auxotroph unable to synthesize histidine)-> mix Salmonella his- with test chemical-> plate on histidine-deficient media-> only revertant his- cells will grow
mutagenesis-> carcinogenesis |
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Missense mutation
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changes AA
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Neutral mutation
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change to equivalent AA
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nonsense mutation
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creates stop codon
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Insertion/Deletion
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caused by intercalating agents (insert themselves between stacked bases of helix, ethidium bromide)
causes distortion of DNA causes "frame shift" mutations |
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Morphological mutants
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change in cell wall, colony morphology
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Lethal mutant
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cell death
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Conditional mutant
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mutation expressed in certain conditions
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Biochemical mutants
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Auxotroph (can't synthesize certain compound)
Prototroph (wildtype) |
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Microbial Recombination
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Process in which >1 nucleic acid molecules are rearrange & combined to produce a new nucleic sequence
Occurs following horizontal gene transfer One-directional Donor-> recipient |
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Vertical Gene Transfer
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genes transferred from parent to offspring
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Horizontal Gene Transfer
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transfer of genes from one mature, independent organism to another
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exogenote
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DNA transferred to recipient
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endogenote
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genome of recipient
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merozygote
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recipient cell that is temporary diploid as result of transfer process
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conjugation
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DNA transfer between bacteria requires direct contact via sex pilus
Can transfer plasmids, episomes, partial or whole chromosomes |
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Plasmids
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cDNA-<30 genes
exist independently of chromosome Have replication origins |
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episome
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plasmid that can integrate into chromosome
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conjugative plasmids
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contain genes for pili & transfer copies of themselves
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Fertility factors
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conjugative plasmids contain genetic info for sex pili formation
Episomes |
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Resistance factors
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have genes for antibiotic resistance
Encode enzymes capable of destroying or modifying antibiotics Usually conjugative plasmids & may contain transposons |
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Col plasmids
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encode bacteriocins
-bacteriocidal=proteins that destroy other bacteria |
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Virulence plasmids
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encode toxin genes-> make host more pathogenic
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Metabolic plasmids
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encode genes for enzymes
some allow degradation of unusual carbon sources |
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Transposable Elements
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segments of DNA that move from one chromosomal location to another
allow movement of genes between chromosome & plasmids allows antibiotic resistance genes to move from chromosome->plasmid-> other cells |
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tra operon
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include genes for pili on F plasmid
most info required for plasmid transfer |
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insertion sequences
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assist plasmid integration into host cell chromosome->allows existence as episome/outside bacterial chromosome
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Bacterial conjugation
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transfer of DNA by direct cell to cell
1946-Lederburg & Tatum mixed 2 auxotrophic strains-> incubated culture for several hours in nutrition media->plated on minimal media->growth |
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U-tube experiment
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Bernard Davis
demonstrated that direct cell to cell necessary after incubation in nutrient medium, bacteria plated on minimal medium-> no prototrophs |
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F+ x F- mating
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cell with fertility factor plasmid transfers plasmid to F- cell
F+ = recipient cell |
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Hfr x F- mating
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Hfr (high frequency of recombination) cell has F factor plasmid integrated into chromosome (exhibits high efficiency of chromosomal gene transfer in comparison with F+ cells)
Transfers part/all of chromosome to F- F- cell remains F- but may recombine with donated DNA DNA transfer begins when integrated F factor nicked at site of transfer origin since only part of F factor transferred at start, F- doesn't become F+ usually |
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Hfr Mapping
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used to map relative location of bacterial genes based on observation that chromosome transfer occurs at constant rate
Interrupted mating experiment "Blender" -Hfr x F- mating interrupted at various intervals -order & timing of gene transfer determined -break conjugation bridge to study sequence of gene entry into recipient |
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Finding E. Coli Genetic Map
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gene locations expressed in minutes, reflecting time transferred
Larger size-> maps from >1 Hfr required-> F plasmid integrated at different locations Multiple maps superimposed-> 0 time=threonine locus |
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F' Conjugation
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F factor in Hfr leaves, may pick up portion of chromosomal DNA-> F-
F' plasmid transferred to F- which then becomes F' cell |
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Transformation
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uptake of "naked" DNA
first observed by Griffith 1928 recipient must be "competent" for DNA uptake -dependent on growth cycle -required expression of proteins needed for transformation smooth/rough DNA experiment |
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Generalized Transduction
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during lytic life cycle of bacteriophage virus assembly may incorporate host genes into progeny virus
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Specialized Transduction
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specific bacterial genes transferred
occurs via bacteriophages with lysogenic life cycles |
