EBIO 3400: FINAL EXAM
104 Cards in this Set
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Generation time
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time it takes for a cell to double
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Antisepsis
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kill most microorganisms on living surface
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Disinfection
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kill most microorganisms on inanimate surface
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Sterilization
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kill all organisms, including endospores
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Sanitation/decontamination
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mechanical removal of organisms from living or inanimate surfaces
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Factors that determine effectiveness of microbial control
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Type of microorganism
Time of exposure
Presence of growth factors
Concentration of antimicrobial agent
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Main cellular targets of antimicrobial agents
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Cell membrane, proteins, DNA
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Moist heat
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Boiling, steam autoclave, pasteurization- faster
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Dry heat
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Longer time, higher heat required- baking
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UV radiation/Gamma radiation
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causes thymine dimers, does not penetrate objects
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Filtration
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removes microbes from fluid or air, pore size is important
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Detergents
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low level disinfectant, disrupts membranes
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Alcohols
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used for disinfection and antisepsis, disrupts membranes and denatures proteins
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Acids/Alkalis
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denature proteins by altering pH, mostly disinfecting, can inhibit fermentation in bacteria
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Oxidizing agents
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used at high levels for sterilization and at low levels for disinfection, kills anaerobic bacteria
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Phenolics
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used for widespread disinfection of surfaces, denatures proteins (Lysol)
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Halogens
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used for sterilization (pools) and antisepsis (surgery), denatures proteins and breaks disulfide bridges (Betadine and chloramine)
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Koch's postulates
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1) Microorganism must be present in all cases of the disease
2) pathogen can be isolated from diseased host and grown in pure culture
3) Pathogen must then cause disease when inoculated into a healthy susceptible lab animal
4) Pathogen must be reisolated from the new host and shown to …
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Limitations of Koch's postulates
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Some organisms cannot be isolated in pure culture such as M. leprosy
Some human diseases are too deadly to ethically inoculate in the lab
Examples: viruses, HIV/AIDS, cholera, yellow fever, H. pylori
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Cell membrane
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Plasma membrane encompassing cytoplasm and defining the cell, innermost layer of cell envelope, selectively permeable
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Fluid mosaic model
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Phospholipid bilayer with floating proteins for stability/structure:
In bacteria no cholesterol: instead, HOPANOIDS
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S Layer
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protein or glycoprotein layer outside cell wall, protective layer of crystallized proteins (think bathroom tiles), helps maintain shape and envelope rigidity and can protect pathogens against host immunity defenses
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Glycocalyx
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layer consisting of network of polysaccharides extending from surface of cell, aids in attachment to solid surfaces
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Capsule
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glycocalyx layer that is well organized and not easily washed off, resists phagocytosis and protects against dessication
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Slime layer
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zone of diffuse, unorganized material, easily removed, can facilitate motility
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Pili (fimbrae)
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fine, hairlike appendages that are thinner and usually shorter than flagella
-can aid in attachment
-can aid in motility and uptake of DNA during bacterial transformation
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Sex pili
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larger than other pili, genetically determined by conjugative plasmids, required for conjugation
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Flagella
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threadlike locomotor appendages extending outward from the plasma membrane and cell wall, main function is motility but can also be involved in attachment
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Filament
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longest and most obvious portion of flagella extends from cell surface to tip, made of flagellin
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Basal body
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portion of flagella embedded in cell envelop
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Hook
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portion of flagella, short curved segment that links filament to its basal body and acts as a flexible coupling
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Capping protein
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end of flagella
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Chemotaxis
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movement towards a chemical attractant or away from a chemical repellent
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Chemoreceptors
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surface receptor proteins that bind chemicals and transmit signals to detect chemical attractants and repellents
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Endospores
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dormant cells formed within mother cells, only produced by Bacillus, Clostridium (rods), and Sporosarcina (cocci) genera (phylum Firmicutes).
-survive harsh conditions (heat, UV, and chemical resistant)
-protects DNA and protein of organism
-good for disease transmission
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Cell envelope
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layers surrounding bacterial cell
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Gram positive cells
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Stain purple
most Firmicutes and Actinobacteria
thick cell wall composed of peptidoglycan and techoic acid, 2 layers
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Gram negative cells
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Stain pink
cell walls are more complex but thinner, 3 layers
peptidoglycan is within periplasmic space
Has lipoplysaccharides (LPS)
less susceptible to antibiotics
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Prokaryotic genome
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Circular (plasmids)
Packaged by negative supercoiling (topoisomerases)
Most of genome is coding
up to about 10 Mbp
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Eukaryotic genome
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linear DNA
packaged with histones
introns
genome is much larger than prokayotic
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Main Doctrine
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DNA replication -> Transcription (RNA) -> translation (protein)
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Spontaneous mutation
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random change in DNA arising from erroneous replication without known cause
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Induced mutation
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results from exposure to known mutagens- chemical or physical agents that damage DNA and interfere with function
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Point mutation
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small, affects only one base: additio, substitution, or deletion of single base
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Missense mutation
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change in code that leads to the placement of a different amino acid, can create a faulty nonfunctional protein, or produce a protein that functions in a different manner, or cause no significant alteration in function
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Nonsense mutation
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change in code that results in a stop codon instead of an amino acid, resulting in shorter than usual protein being translated; usually very harmful, almost always results in nonfunctional protein
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Silent mutation
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change in base but not change in amino acid, no change to protein
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Back mutation
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when a gene that has undergone mutation reverses (mutates back) to its original base composition
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Frameshift mutation
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most harmful/damaging, changes the reading frame
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Genetic recombination
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production of offspring with combinations of traits that differ from those found in either parent
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Conjugation
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horizontal gene transfer, requires attachment of two related species and formation of bridge, donor cell with a pilus, and fertility plasmid in donor. Both donor and recipient must be alive.
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Cloning
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-Cut DNA into smaller fragments
-Insert into cloning vector (usually a plasmid)
-Introduce into host organism, grow cells
-Sequence individual fragments
-PCR
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Primary Factors controlling microbial growth
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Temperature, pH, osmolarity, gas/oxygen
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Cardinal temperatures
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range for microbial growth
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Minimum temperature
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lowest temperature that permits a microbe's continued growth and metabolism, below this temperature all activities are inhibited
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Maximum temperature
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highest temperature that growth and metabolism can proceed, growth stops if higher than this temperature. if temperature continues to rise, enzymes and DNA become denatured causing cell death
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Optimum temperature
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small range between minimum and maximum which promotes fastest growth and metabolism
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Psychrophile
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optimum temp below 15 C, capable of growth at 0 C
Habitats: lakes, snowfields, polar ice, deep ocean
Listeria
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Psychrotroph
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Facultative psychrophile, can survive at cold temperatures and grow slowly, but optimum temperature is above 20 C
Staph. aureus
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Mesophiles
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optimum temp between 20 and 40 C
Bacillus and Clostridium
Most human pathogens (30-40 C)
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Thermoduric microbes
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can survive short exposure to high temp, common contaminant of heated or pasteurized food; mesophile
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Giardia
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heat resistant cysts; mesophile
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Thermophile
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grows optimally above 45 C, usually (45 to 80C)
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Hyperthermophile
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80 to 250 C
Habitats: soil and water around volcanoes, or directly exposed to sun
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Thermos aquaticus
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hyperthermophile that produces Taq polymerase
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Taq polymerase
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heat resistant polymerase produced by Thermos aquaticus, used in polymerase chain reaction to amplify DNA
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Neutrophiles
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most microbes, survives at or near pH7
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Acidophiles
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microbes that thrive in highly acidic habitats (acid lakes, acidic bogs), some maintain low pH needed for growth by releasing strong acids
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Alkalinophiles
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microbes that thrive in basic habitats (hot pools or soil, up to pH 10)
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Proteus spp.
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Alkalinophile bacteria that decomposes urea in urine, creating NH4+ and neutralizing acidic urine, allowing it to colonize and infect urinary system
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Osmotic environment preferred by most microbes
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Hypotonic or isotonic
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Osmophiles
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live in habitats with high solute concetration
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Halophiles
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type of osmophile requiring high salt concentration, living in salt lakes, salt ponds, or other hypersaline environments, grows optimally in solutions 25% NaCl, requires at least 9% NaCl. Significant modifications in cell walls and membranes, will lyse in hypotonic solution
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Osmotolerant
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can adapt to wide concentration in solutes, resistant to salt but do not normally live in high salt environments (Staph. aureus)
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Singlet oxygen
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extremely reactive, produce by phagocytes to kill invading bacteria
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Aerobe
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uses oxygen in metabolism and can detoxify it, has enzymes to process toxic oxygen products
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Obligate aerobe
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cannot grow without oxygen; Fungi, protozoa, and some bacteria (Micrococcus and Bacillus)
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Facultative anaerobe
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does not require oxygen for metabolism, metabolizes by aerobic resp. when oxygen is available, when oxygen absent adopts anaerobic mode of metabolism such as fermentation, usually has catalase and superoxide dismutase
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Microaerophile
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does not grow at normal atmospheric concentration of oxygen, instead requires very small amount for metabolism (1-15%). Habitat such as soil, water, or human body.
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Anaerobe
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cannot use or detoxify oxygen, lacks metabolic enzymes to use oxygen in respiration
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Strict obligate anaerobes
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ack enzymes to process toxic oxygen, cannot tolerate free oxygen in immediate environment and will die if exposed to oxygen, live in highly reduced habitats such as deep mud, lakes, oceans
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Aerotolerant anaerobes
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don't use oxygen but can detoxify it and survive in its presence
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Lactobacilli
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aerotolerant anaerobe inactivates peroxide and superoxide with manganese ions
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Anaerobic pockets
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Microhabitats in human body allowing colonization by anaerobic bacteria such as dental cavities, gingivitis, and large intestine
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Autotrophs
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Produces own nutrients, CO2 absolutely essential
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Canophiles
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grow best at high CO2 concentration 3-10% (atmospheric is typically 0.033 %)
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Substrate level phosphorylation (ATP production)
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ATP produced, less than oxidative phosphorylation, occurs in citric acid cycle
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Oxidation
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losing electrons
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Reduction
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gaining electrons
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Aerobic respiration
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glycolysis, TCA cycle, and ETC
Most ATP produced via oxidative phosphorylation in ETC
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Anaerobic respiration
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similar but terminal electron receptor is not oxygen
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Fermentation
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partial breakdown of organic food without net transfer of electrons to an inorganic terminal electron receptor
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Lactic acid fermentation
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pyruvate generated from glycolysis is reduced to lactate via electrons on NADH
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Alcohol fermentation
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sugars such as glucose, fructose, and sucrose are converted into cellular energy and thereby produce ethanol and carbon dioxide as metabolic waste products
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Carbon source: autotroph
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CO2
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Carbon source: heterotroph
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Reduced, preformed, organic molecules from other organisms
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Energy source: phototroph
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Light
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Energy source: chemotroph
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oxidation of organic or inorganic compounds
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Electron source: lithotroph
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reduced inorganic molecules
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Electron source: organotroph
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organic molecules
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Advantages of fermented food
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Less prone to spoilage, more easily digested, and can add nutrients or flavors
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Wine
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typically primary fermentation of sugars to ethanol by Saccharomyces (fungus) followed by secondary malolactic fermentation by bacteria
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Cheese
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primary fermentation by lactic acid bacteria, lowers pH making casein (milk protein) insoluble and causing it to coagulate (accelerated by adding rennet proteases)
Secondary fermentation can be bacterial or fungal
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Vegetable fermentation
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pickles, sauerkraut, kimchi, fermentation by acetic acid or lactic acid bacteria
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EBIO 3400: FINAL EXAM