Microbio 310: Exam 1
74 Cards in this Set
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Characteristicsof living systems
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1.Metabolism: chemical transformation of nutrients
2.Reproduction: generation of two cells from one
3. Differentiation: synthesis of new substances or structures that modify the cell
4.Communication: generation of, and response to, chemical signals
5.Movement: via self-propulsion, man…
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Antoni van Leeuwenhoek
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the first person to describe bacteria
built single lens magnifier
looked at water droplet and stool sample and found living creatures (giardia - eukaryotic parasite)
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Louis Pasteur
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discovered that living organisms discriminate between optical isomers
discovered that alcoholic fermentation was a biologically mediated process (originally thought to be purely chemical)
disproved theory of spontaneous generation
led to the development of methods for controlling the g…
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Robert Koch
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demonstrated the link between microbes and infectious diseases
identified causative agents of anthrax and tuberculosis
developed techniques (solid media) for obtaining pure cultures, some still in existence today
father of medical microbiology
awarded nobel prize for physiology and me…
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Koch's postulates
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1. the suspected pathogen must be present in all cases of the disease and absent from healthy animals (microscopy, staining)
2. The suspected pathogen must be grown in pure culture (laboratory culture)
3. Cells from a pure culture of the suspected pathogen must cause disease in a health…
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Diseases with no available animal model
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cholera, rickettias, chlamydias
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Pure cultures
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Koch discovered that using solid media provides a simple way of obtaining pure cultures
began with potato slices, but eventually devised uniform and reproducible nutrient solutions solidified with gelatin and agar
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Light microscopy
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compound light microscope uses visible light to illuminate cells
many different types:
bright-field
phase-contrast
dark-field
fluorescence
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Bright field scope
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specimens are visualized because of differences in contrast (density) between specimen and surroundings
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Resolution
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the ability to distinguish two adjacent objects as separate and distinct
determined by wavelength of light used and numerical aperture of lens
limit of resolution for light microscope is 0.2 um
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Stains
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improves contrast
dyes: organic compounds that bind to specific cellular materials
examples: methylene blue, safranin, and crystal violet
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Steps to staining
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1. preparing a smear: spread culture in thin film over slide > dry in air
2. Heat fixing and staining: pass slide through flame to heat fix> flood slide with stain; rinse and dry
3. Microscopy: place drop of oil on slide; examine with 100 x objective lens
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Phase-contrast microscopy
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invented by Frits Zernike
phase ring amplifies differences in the refractive index of cell and surroundings
improves the contrast of a sample without the use of a stain
allows for the visualization of live samples
resulting image is dark cells on a light background
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Dark-field microscopy
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light reaches the specimen from the sides
light reaching the lens has been scattered by specimen
image appears light on a dark background
excellent for observing motility
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Fluorescence microscopy
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used to visualize specimens that fluoresce
emit light of one color when illuminated with another color of light (cyanobacteria)
cells fluoresce naturally (autofluorescence) or after they have been stained with a fluorescent dye like DAPI
widely used in microbial ecology for enumerating…
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Differential Interference Contrast (DIC) Microscopy
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uses a polarizer to create two distinct beams of polarized light
gives structures such as endospores, vacuoles, and granules a three-dimensional appearance
structures not visible through bright-field are sometimes visible through DIC
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Atomic Force Microscopy (AFM)
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a tiny stylus is placed close to a specimen
the stylus measures weak repulsive forces between it and the specimen
a computer generates an image based on the data received from the stylus
good for looking at fine surface structure, not inside of cell
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Confocal Scanning Laser Microscopy
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uses a computerized microscope coupled with a laser source to generate a three-dimensional image
computer can focus the laser on single layers of the specimen
different layers can then be compiled for a three-dimensional image
gives better resolution than traditional fluorescent micros…
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Electron Microscopy
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uses electrons instead of photons to image cells and structures
two types:
transmission electron microscopes (TEM)
scanning electron microscopes (SEM)
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Transmission Electron Microscopy (TEM)
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electromagnets function as lenses
system operates in a vacuum (completely dry)
high magnification and resolution
enables visualization of structures at the molecular level
specimens must be very thin (20-60 nm) and be stained
cannot see live cells
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Scanning electron microscopy (SEM)
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specimen is coated with a thin film of heavy metal (gold) to diffract electrons
an electron beam scans the object
scattered electrons are collected by a detector and an image is produced
even very large specimens can be observed
magnification range of 15x-100,000x
can only see surfac…
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Lynn Margulis
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proposed the endosymbiotic theory
mitochondria and chloroplasts were bacteria engulfed by eukaryotic cell
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Cell morphologies
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coccus: spherical, ovoid
rod: cylindrical
spirillum: spiral shape
cells with unusual shapes:
spirochetes
appendaged (stalk, hypha)
filamentous bacteria
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Selective forces of microbe morphology
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opimization for nutrient uptake (small cells with big SA:V ratio)
swimming motility; or near suface of water (helical or spiral shaped cells)
gliding motilty (ex=filamentous bacteria ,stringy)
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Hopanoid
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A molecule that may help stabilize the phospholipid bilayer of some bacteria, like cholesterol in humans
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Gram-positive cell walls
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teichoic acids (acidic substance embedded in cell wall) - gives additional strength to cell wall, repeating unit of ribitol
lipoteichoic acids: teichoic acid covalently bound to membrane lipids
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Prokaryotes that lack cell walls?
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- mycoplasmas - group of pathogenic bacteria
(pathogen that causes pneumonia, similar to gram positive, but in their life cycle they don’t need cell wall, so they got rid of it)
- thermoplasma - species of archaea
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Gram-negative cell walls
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thin layer of peptidoglycan
composed of outer membrane (lipopolysaccharide [LPS] layer)
endotoxin: toxic component of LPS
porin is a channel to which any small molecule can migrate through, so it’s not giving too specific protection against the outside environment, small molecules can …
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Cell walls of Archaea
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no peptidoglycan
typically no outer membrane
pseudomurein: polysaccharide similar to peptidoglycan
some archaea lack pseudomurein (only in certain methanogenic archaea)
S-layer: most common cell wall type of archaea
protein or glycoprotein
paracrystalline structure
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Capsules and slime layers
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very ery unstructured areas where a slimy layer of polysaccharides are protecting bacteria from immune cells and others coming into the cell, additional protective layer
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fimbriae
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filamentous protein structures
enable organisms to stick to surfaces or form pellicles
surround the whole cell
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pili
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involved in conjugation, a method for extending genetic material for bacteria
twitching motility is caused by type IV pili
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carbon sources of bacteria
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poly-B-hydroxybutyric acid (PHB)
glycogen
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polyphosphate
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accumulation of inorganic phosphate, which is hard to obtain from environment, so cells obtain from this
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sulfur globules
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composed of elemental sulfur
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magnetosomes
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magnetic particle stored in cell in vesicles used to orient themselves on magnetic field of earth to find nutrients
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endospores
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highly differentiated cells resistant to heat, harsh chemicals, and radiation
"dormant" stage of bacterial life cycle
ideal for dispersal via wind, water, or animal gut
only present in some gram-positive bacteria
dipicolinic acid makes a complex that binds to water molecules and dehyd…
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Iron
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cytochromes and FeS for electron transport
anoxic conditions: ferrous (Fe2+)
oxic conditions: ferric (Fe3+)
siderophores: iron binding agents that transport iron into cell (gets reduced Fe3+ to Fe2+)
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growth factors
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organic compounds required for growth, cannot be synthesized, small amounts, not needed by all organisms, purines/pyrimidines, aa's, vitamins
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defined media
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precise chemical composition is known
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complex media
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culturing medium that contains nutrients released by the partial digestion of yeast, beef, soy, or other proteins, thus, the exact composition is unknown
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Selective Media
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contains compounds that inhibit the growth of a specific group of microbes while allowing the growth of another group of microbes.
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differential media
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contains an indicator, usually a dye, that detects particular chemical reactions occurring during growth
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quinones
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hydrophobic, non protein, accepts electrons and protons but passes along electron only
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Fts
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filamentous temperature sensitive proteins
essential for cell division in all prokaryotes
interact to form the divisome (cell division apparatus)
FtsZ forms ring around center of cell; related to tubulin
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MinCD and MinE
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MinCD occilates in response to MinE which forces FtsZ to form ring around center
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MreB
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major shape determining factor in prokaryotes
MreB is another cytoskeleton protein similar to actin, forms a spiral in rod shaped bacterial cells
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Crescentin
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shape-determining protein produced by vibrio-shaped cells of Caulobacter crescents
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autolysins
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beginning at the FtsZ ring, small opening in the wall are created by autolysins, which creates a wall band
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glycosylases
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enzymes that interact with bactoprenol (hydrophobic alcohol that carries cell wall precursors across cytoplasmic membrane)
insert cell wall precursors into growing points of cell wall
catalyze glycosidic bond formation
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transpeptidation
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final step in cell wall synthesis
forms peptide cross links between muramic acid residues in adjacent glycan chains
inhibited by penicillin
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batch culture
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a closed system microbial culture of fixed volume
eventually they die because of lack of nutrients and toxic waste
four phases:
lag
exponential (log) healthiest state
stationary - growth rate is zero, nutrient used up or toxic products accumulate
death
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continuous culture
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an open system microbial culture of fixed volume
chemostat: most common type of device used
both growth rate and population density can be controlled independently and simultaneously
can control:
dilution rate: rate at which fresh medium is pumped in and spent medium is pumped out (co…
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flow cytometer
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alternative method to microscopic counts
uses laser beams, fluorescent dyes, and electronics
mostly mammalian cells
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viable counts
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measurement of living, reproducing population
spread plate and pour plate method
30-300 colonies
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Great Plate Anomaly
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direct microscope counts of natural samples reveal far more organisms than those on plates
-microscopes count dead cells, viable methods do not
-microbes have different growth requirements
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turbidimetric methods
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particles like bacteria in a solution SCATTER light in a beam of light. turbidity is measured by absorbance (optical density). uses a SPECTROPHOTOMETER
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Psychrophile
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Term describing bacteria that love to grow at cold temps
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Mesophile
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bacteria that grows best at moderate temperature
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thermophile
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grow at high temps
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hyperthermophile
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grow at very high temp
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Molecular Adaptations to Psychrophily
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Cold active enzymes:
more α-helices than β-sheets, fewer weak bonds
More polar and fewer hydrophobic amino acids
Decreased interactions between protein domains
Cyto. Memb. modified for optimal transport at low temp.
High unsaturated fatty acid content.
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Molecular Adaptations to Thermophily
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increased number of ionic bonds between basic and acidic amino acids
production of solutes help stabilize
bacteria have lipids rich in saturated fatty acids
archaea have lipid monolayer instead of bilayer
produce enzymes for industrial microbio
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Signal sequences
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found on proteins requiring transport; 15-20 residues long and at the beginning of protein molecule; single the cell's secretory system (Sec system); prevent protein from completely folding
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TAT
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twin argenine translocation
signal sequence motif -- open and close due to binding
maintain conformation
translocates folded proteins (one conformation)
four tat proteins: tat A,B,C, and E are the main ones
no leakage
co-factor in cytoplasm
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RNA interference
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Eukaryotic defense against dsRNA viruses, cleaves dsRNA, destroys ssRNA corresponding to target dsRNA
triggered by dsRNA longer than 20 bp
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Catabolite repression
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allows bacteria to adapt quickly to a preferred carbon and energy source first. This is usually achieved through inhibition of synthesis of enzymes involved in catabolism of carbon sources other than the preferred one.
lactose maltose, flagella
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helix-turn-helix motif
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two α-helical segments linked by the "turn"
the helical segments fit snug in the major groove of the DNA molecule, helping to ensure the proper position of the recognition helix
usually in pairs
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Quorum Sensing
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The exchange of extracellular molecules that allows microbial cells to sense cell density
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autoinducer
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autoinducer
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stringent response
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global control mechanism triggered by amino acid starvation
triggered by (p)ppGpp
alarmones: produced by RelA to signal amino acid starvation
rRNA and tRNA synthesis decreases
amino acid synthesis increases
when RelA is not charged by amino acid presence, it produces pppGpp, which pr…
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Heat shock response
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DnaK (refold denatured proteins) and RpoH (alternative sigma factor that transcribes heat shock proteins)
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traponema pallidum
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syphilis
unculturable in lab
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Cyanobacteria
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Carry out photosynthesis using chlorophyll, responsible for the appearance of oxygen in Earth's early atmosphere
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Microbio 310: Exam 1