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161 Cards in this Set
- Front
- Back
What is a microbe? |
A living organism that requires a microscope to be seen |
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Some microbes consist of a ___________ cell. |
single |
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Name some microbial cell sizes |
Supersize Microbial communities Viruses |
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Microbes include members of the three domains of life: |
Bacteria Archaea Eukarya |
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Bacteria and Archaea include what? |
Prokaryotes |
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Eukarya include what as what? |
Algae and plants Fungi and animals Protists Eukaryotes |
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Define resolution |
the smallest distance by which two objects can be separated and still be distinguished |
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What is thee resolution of the human retina? |
150 micrometers (1/7 mm) |
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Define magnification: |
An increase in the apparent size of an image to resolve smaller separations between objects |
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Light microscopy uses? |
uses light to resolve images of individual cells |
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What are the 4 visualizations through LIGHT MICROSCOPY? |
- Bright-field - Dark-field - Fluorescence - Phase contrast |
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Bright-field: Light or electron? |
images viewed as dark objects against light-filled field LIGHT |
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Dark-field: Light or electron? |
images viewed as halos of bright light against darkness LIGHT |
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Fluorescence: Light or electron? |
incident light is absorbed by the specimen and reemitted at a longer wavelength LIGHT |
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Phase contrast: Light or electron? |
Reveals differences in refractive index as patterns of light and dark LIGHT |
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Electron microscopy uses: |
uses electrons to resolve images. Electrons behave light light waves. |
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What are the two patterns from electron microscopy? |
Scanning (SEM) Transmission (TEM) |
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Scanning (SEM): Light or Electron? |
electrons SCAN the outer surface. Reveals external features Reveals external features in 3D ELECTRON |
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Transmission (TEM): Light or Electron? |
electrons PASS through the specimen. Reveals internal structures. Reveals internal structures in 2D ELECTRON |
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How to increase resolution under Bright-Field Microscopy? |
Use shorter wavelength light (higher energy) Use immersion oil |
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The detection and resolution of cells under a microscope are enhanced by: |
Fixation Staining |
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Fixation: |
Cells are made to adhere to a slide in a fixed position |
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Staining: |
Cells are given a distinct color |
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Name the four differential stains for bright microscopy: |
Gram stain Acid-fast stain Spore stain Negative stain |
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Gram positive V Gram negative |
Gram positive retains the crystal violet stain because of their thicker cell wall Gram negative bacteria do not |
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Acid-fast stain |
Carbolfuchsin used to stain Mycobacterium species |
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Spore stain |
Malachite green used to decect spores of Bacillus and Clostridium |
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Negative stain |
Colors the background, which makes capsules more visible |
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Which kind of microscopy detects scattered light normally missed with bright field? What does t require to detect the scattered light? |
Dark field microscopy A modified condenser |
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Which kind of microscopy can see flagella? |
Dark field |
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What can Phase-contrast be used to view? |
Live cells and cellular organelles |
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Light patterns: Dark field = Phase Contrast = |
Scattering Refraction |
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How does Phase Contrast work? |
1. The specimen retards light by 1/4 of wavelength 2. The phase plate (coated with refractive material) retards light again by 1/4 wavelenth 3. Light is now retarded by 1/2 wavelength 4. Light from the specimen and the transmitted light are completely out of phase (PHASE-CONTRAST) 5. When both lights reach the eye the image appears dark against bright background |
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How does fluorescence Microscopy work? |
The specimen is first stained with a fluorophore. The fluorophore absorbs light at a certain wavelengh, The light is them emitted at a higher wavelength, The eye sees that a fluorescent color corresponding to the emission wavelength. More than one fluorophore can be used on the same sample to "label" different structures, e.g. membrane and nucleus |
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What is a fluorophore? |
A fluorescent molecule |
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In electron microscopy, electrons behave like light waves but they have: |
- Very high frequency - allows very great resolution, a few nanometers |
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How does electron microscopy get the sample to absorb electrons? |
COATED WITH HEAVY METAL TO MAKE THEM ABSORB ELECTRONS |
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Sample preparation for Electron Microscopy: |
The specimens are: 1. Embedded in a polymer for thin sections - microtome is used to cut slices 2. The specimen is then treated with a heavy-metal salt such as uranyl acetate *Note: For SEM, specimen is coated with heavy metal and it is not sliced |
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Most prokaryotes share fundamental traits: |
- Thick, complex outer envelope - Compact genom - Tightly coordinated cell functions |
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Cytoplasm |
Consists of gel-like network |
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Cell membrane |
Encloses the cytoplasm |
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Cell wall |
Covers the cell membrane |
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Nucleoid |
Non-membrane bound area of the cytoplasm that contains the chromosome in the form of looped coils |
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Flagellum |
External helical filament whose rotary motor propels the cell |
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What is the structure that defines the existence of a cell? |
Cell membrane |
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What are cell membranes made up of? |
Phospholipids and proteins |
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Describe the structure of a phospholipid |
Water loving head ad lipid loving tail - They are arranged in a bilayer |
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Membrane proteins serve numerous functions: |
- Structural support
- Detection of environmental signals - Secretion of virulence factors and communication signals - Ion transport and energy storage |
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Microbial cells can range from: |
a few nanometers to a fraction of a millimeter in size |
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Microscopes increase _____________ by increasing ______________. |
RESOLUTION MAGNIFICATION |
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What can cross the cell membrane? |
Small uncharged particles such as O2 and CO2, easily permeate the membrane by passive transport Water tends to diffuse across by osmosis |
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What cannot cross the membrane? |
charged particles like sugars and vitamins Ions |
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For the molecules that cannot get across the membrane freely, how do they get across? |
Transporter proteins help them cross to the cytoplasm |
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Name the two kinds transport. |
Passive and Active |
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Passive transport: |
Along concentration gradient, e.g. from high concentration outside the cell to the low concentration in the cytoplasm |
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Active transport: |
against concentration gradient; requires expenditure |
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What cell organ is the outside layer of the cell? |
The cell wall |
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What does the cell wall do? |
Confers shape and rigidity to the cell, and helps it withstand turgor pressure |
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Most bacterial cell walls are made up of ______________. |
peptidoglycan |
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Peptidoglycan is made up of ________ and _________. |
peptides and glycan glycan = sugar |
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Bright field: resolution increases by ____________ and ___________. |
FIXATION and STAINING |
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In bright field microscopy, dark objects appear on a bright background. Resolution is enhanced by using________, e.g. Gram, Spore, Acid-fast, negative.On the other hand, in fluorescence microscopy, objects are labeled with__________that absorb light at a certain wavelength and emit it at a higher wavelength. |
Stains and Fluorophores |
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Coupled transport where the 2 molecules move in the same direction is known as ____, while coupled transport where the 2 molecules move in opposite direction is known as ______ |
Symport and Antiport |
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Both ABC transporters and group translocation transporters require energy expenditure. This is manifested in the form of ATP hydrolysis for both kinds of transporters. TRUE OR FALSE |
False
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If you have a mixture of 2 organisms A and B that you want to separate into pure cultures, you can either use a selective medium to grow one but not the other, or a differential medium that allows growth of both organisms, albeit with a different phenotype. TRUE OR FALSE |
True |
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List the four phases of the bacterial growth curve IN ORDER. |
Lag Log Stationary phase Death phase |
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Compared to Gram-positive bacteria, Gram-negative bacteria have an ______ composed mainly of _______ |
Outer membrane Lipopolysaccharide(LPS) |
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The bacterial cell wall is made up of peptidoglycan, whose glycan backbone consists of repeating ______and______, while the bacterial cell membrane is made up of______and a bilayer of______ |
NAG NAM Phospholipids Proteins |
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What is a cell envelope? |
Everything outside the plasma membane |
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What do envelope layers do? |
Provide structural support and protection |
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Difference between Gram + and Gram - bacteria |
+ has thick cell wall and - has thin cell wall + has amino acid cross links in peptidooglycan and - has an outer membrane composed of LPS |
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List the three main structural components of Lipopolysaccharide |
Lipid A Core polysaccharide O-antigen or -polysaccharide |
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Which component of the LPS is the toxic portion? |
Lipid A |
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Organisms surviving under conditions outside the "normal" ranges are known as _______. They are able to do so since their ______ are best suited for these conditions. |
Extremophiles proteins and macromolecules |
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What is endotoxin? |
a component that can stimulate host immune response |
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LPS of G- bacteria acts as ___________. |
Endotoxin |
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Eukaryotes have a __________________ nucleus. |
membrane-bound |
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Prokaryotes have a ____________ region that extends throughout the cytoplasm. |
nucleoid |
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What does the nucleoid contain? |
DNA strands |
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Pili or fimbriae: |
straight filaments of protein monomers called pilin |
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What is the function of pili or fimbriae? |
Attachment or adherence to surfaces |
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Sex pili: |
involved in conjugation (transfer of DNA from a donor cell to a recipient cell) |
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Name three external structures of a cell. |
Pili or fimbriae Sex pili Flagella |
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Peritrichous: |
Cells have flagella randomly distributed around the cell |
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Lophotrichous: |
cells have flagella at the end(s) |
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Monotrichous: |
cells have a single flagellum |
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Each flagellum is a spiral filament of protein monomers called ___________. |
Flagellum |
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Where does the energy come from for rotation of the flagella? |
ATP Hydrolysis |
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Macronutrients: |
major elements in cell macromolecules (carbs, proteins, lipids) They are ions necessary for protein function |
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Micronutrients: |
Trace elements necessary for enzyme function |
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Selective permeability is achieved in 3 ways: |
1. Membrane-spanning protein channels or pores -> those are like facilitated diffusion transporters 2. Substrate-specific carrier proteins, or permeases that span the membrane -> those are common in active coupled transport 3. Dedicated substrate-binding proteins that are present in the periplasmic space -> those are part of ABC transporters |
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What is periplasmic space? |
space between inner and outer membranes |
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What does passive transport do? |
Helps solutes move across a membrane from a region of high concentration to one of lower concentration |
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Does passive transport require energy? |
It does not and it cannot move a molecule against its gradient |
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It is the ____________ family that transports water and small polar molecules such as glycerol. |
aquaporin |
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What are coupled transport systems? Passive or active? |
They are those in which energy released by moving a driving ion down its gradient is used to move a solute up its gradient. ACTIVE |
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What happens in symport? |
two molecules travel in the same direction |
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What happens in antiport? |
the actively transported molecule moves in the direction opposite to the driving ion |
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What kind of transport is symport? |
Active coupled transport |
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What kind of transport is antiport? |
Active coupled transport |
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What does ABC stand for in ABC transporters? |
ATP-binding cassette superfamily |
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Active ABC transporters have two main types: |
- Uptake ABC transporter are critical for transporting nutrients - Efflux ABC transporters are generally used as multidrug efflux pumps |
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What is group translocation? |
the process that uses energy to chemically alter the substrate during its transport "Active Translocation" |
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What is an example of group translocation and is present in all bacteria? |
phosphotransferase system (PTS) |
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How does PTS work? |
First a phosphate group is attached to specific sugars (e.g. glucose -> glucose-P) Because the transported molecule is chemically different than the molecule outside the cell, it is not considered moving against its concentration gradient. But this transport could still be considered active since it requires energy expenditure in the first step where the substrate is chemically modified. |
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Culture medium is of two main types: |
Liquid or broth Solid (usually gelled with agar) |
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What are the two main techniques in isolating colonies? |
Dilution streaking Spread plate |
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What are the types of culture media? |
Complex Synthetic (also called defined medium) Selective Differential |
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Complex media: |
Nutrient-rich but poorly defined (e.g. components like yeast extract in a medium provides nutrients but its composition is not defined) |
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Synthetic media: |
(also called defined medium) are precisely defined
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Selective media: |
Favor the growth of one organism over another (one will grow and the other will not) |
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Differetial media: |
exploit differences between two species that grow equally well in the medium but display a different phenotype |
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Most bacteria divide by ______________, where one parent cell splits into 2 equal daughter cells. |
binary fission |
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What is generation time? |
the time is takes for a population to double |
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What are the 4 phases of the bacterial growth curve? |
1. Lag phase 2. Log phase 3. Stationary phase 4. Death phase |
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Lag phase: |
Bacteria are preparing their cell machinery for growth |
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Log phase: |
Growth approximates an exponential curve (straight line, on a logarithmic scale) |
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Stationary phase |
Cells stop growing and shut down their growth machinery while turning on stress responses to help retain viability |
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Death phase |
Cells die with a "half-life" similar to that of radioactive decay, a negative exponential curve. |
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In nature, many bacteria form specialized, surface-attached communities called _________. |
biofilms |
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How does biofilm formation start? |
By attachment of cells to a surface followed by formation of microcolonies that ultimately grow into mature biofilms. |
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___________ and ____________ species can produce dormant spores that are heat-resistant. |
Clostridium Bacillus |
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With bacterial endospores, When conditions become unfavorable for growth, e.g. during starvation, what happens? |
spore-forming bacteria initiate endospore formation |
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With bacterial endospores, when conditions become favorable again, what happens? |
Endospores germinate into vegetative cells |
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What do endospores contain? |
the genetic material of the cell |
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Group translocation modifies the substrate during _________ and requires energy expenditure. |
transport |
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Any ecological niche outside this window is called "extreme" and organisms inhabiting them are called _______________. |
extremophiles |
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What are "normal" or non-extreme growth conditions for microorganisms are: |
Sea-level temp 20 to 40 degrees C neutral pH 0.9% salt ample nutrients |
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Being able to survive and thrive in an environment (extreme or non-extreme) depends on the tolerance of that organism's _________________________________________ to the physical conditions within that environment. |
proteins and other macromolecular structures |
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Each organism has an "__________" temp, as well as a min and max temp that define its growth limits. |
optimum |
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The growth temp of psychrophiles |
0 to 20 degrees C |
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The growth temp of mesophiles |
15 to 45 degrees C |
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The growth temp of thermophiles |
40 to 80 degrees C |
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The growth temp of hyperthermophiles |
65 to 121 degrees C |
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What are barophiles or piezophiles? |
Organisms adapted to grow at very high pressures. Up to 1,000 atm |
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Barotolerant organisms grow well over the range of _____________, but their growth falls off thereafter. |
1 - 50 MPa |
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Why are many barophiles also psychrophiles? |
the avg temp at the ocean floor is 2oC |
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Halophiles require what? |
high salt concentrations |
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pH of growth range for Neutralophiles |
pH 5 - 8 |
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pH of growth range for Acidophiles |
pH 0 - 5 |
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pH of growth range for Alkliphiles |
pH 9 - 11 This high pH is typically found in soda lakes and so organisms are also halophilic |
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____________ can only grow in oxygen. |
Strict aerobes |
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______________________ grow only at lower O2 levels. |
Microaerophiles |
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_______________ die in the least bit of oxygen. |
Strict anaerobes |
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_________________________ can live with or without oxygen. |
Facultative anaerobes |
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In natural environments, nutrient concentrations are typically ______. |
low |
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Define Eutrophication |
the sudden intro of large quantities of a formerly limiting nutrient It can lead to a "bloom" of microbes, which can threaten the existence of competing species |
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What are some terms used to describe antimicrobial control measures? |
Sterilization Disinfection Antisepsis Sanitation |
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Define sterilization |
killing of all living organisms |
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Define disinfection |
killing or removal of pathogens from inanimate objects Might not kill non-pathogenic microorganisms and so is not considered sterilization |
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Define antisepsis |
Killing or removal of pathogens from the surface of living tissues, e.g. skin |
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Define sanitation |
reducing the microbial population to safe levels |
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Physical Agents to kill microbes: |
1. High temp 2. Pasteurization 3. Filtration 4. Irradiation |
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Most heat is more effective than dry heat. _______________ kills most cells. |
Boiling water |
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What does killing spores and thermophiles usually require? |
A combination of high pressure and temp |
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What does irradiation involve? |
Ultaviolet gamma rays, electron beams and xrays |
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Chemical agents to kill microbes: |
Commercial disinfectants and antiseptics - ethanol - iodine - chlorine |
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What are antibiotics? |
Chemical compounds synthesized by one microbe that kill or inhibit the growth of other microbial species |
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What does LTLT stand for? |
(low temp/long time) - 63 degrees C for 30 minutes |
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What does HTST stand for? |
(High-temp/short time) - 72 degrees C for 15 seconds |
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Both process of LTLT and HTST kill what? |
Coxiella burnetii, the casuative agent of Q fever |