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66 Cards in this Set
- Front
- Back
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Microorganisms are usually around 10^____ |
10^-8 |
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What is the limit of resolution quantitatively and qualitatively? |
Quantitative: 0.2micron Qualitative: We cannot see anything smaller than the wavelength of light which is 200nm, thus we cannot see anything smaller than 0.2 microns, thus light will just bend around the object |
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What is the length and width of E. Coli? |
0.2 micron wide and 3.0 micron long |
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What is the theoretical limit of light magnification? What are the 2 ways that would one circumvent this? |
1000x This can be circumvented by: 1) Changing the wavelength of energy we're using to observe the microorganisms Ex: Electrons 2) Attach a fluorophore and use fluorescence microscopy |
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What is the function of staining and what is the most commonly used stain? |
In order to increase contrast for bright-field microscopy Gram Stain |
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How does the gram stain work? What is the resulting color of the stained cell? |
Gram discovered that crystal violet kills bacteria, but upon addition of iodine, the crystal violet precipitates forming crystals inside the cell wall. The cell is then purple |
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What are the 4 steps of a gram stain? |
1) Flood heat-fixed cells crystal violet for 1 min 2) Add iodine for 1 min 3) Decolorize unstained cells with alcohol for ~20sec. This leaves gram-positive cells purple/violet and gram-negative cells colorless 4) Counterstain with safranin for 1-2 min to make the gram negative cells pink/red |
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Why does safranin work as a counterstain? |
Safranin is a weaker stain then the gram stain and thus only stains the unstained cells without impacting the already stained cells |
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What are the 4 types of 2 dimensional cell imaging and how do they work? |
1) Bright-field microscopy - Look at it with light 2) Phase-contrast - Takes differences in refractive indices and translates them to contrast 3) Dark-Field - Excludes the unscattered beam from the image, so you only see the cell 4) Fluorescence microscopy - add fluorochrome |
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What are the 4 types of 3 dimensional cell imaging and how do they work? |
1) Differential Interference Contrast - Generates contrast similar to phase-contrast but adds depth and ridges for 3D 2) Atomic Force - Atomic repulsions get translated to an image 3) Confocal Scanning -2Dslices in high resolution 4) Electron microscopy - TEM and SEM |
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How does transmission and scanning electron microscopy differ? |
Transmission tunnels through thin slices Scanning only does topology and requires dehydration of cell then coating it in a heavy metal |
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What are the 7 components of a prokaryotic cell? |
1) Cytoplasmic membrane 2) Cell wall 3) Ribosomes 4) Inclusion: storage polymers/magnetosomes 5) Nucleoid 6) Chromosome 7) Flagellum |
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What are 6 basic morphologies of bacteria? |
1) Coccus 2) Rod (Bacillus) 3) Spirilium 4) Spriochete 5) Budding and Appendaged 6) Filamentous |
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How do we differentiate between spirilium and spirochete? |
Spirilium is helical whereas spirochete are twisted like a rope. Spirochete are way more twisted |
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Any protrustion that includes ______ falls into the budding and appendaged catagory |
Cytoplasm |
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How does the average size of a prokaryote compare to that of a eukaryote? |
Prokaryotes < Eukaryotes Prokaryote: 0.1-50nm Eukaryote: 2.0-200nm |
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How does a gram positive compare and contrast to a gram negative cell? |
Both have a cytoplasmic membrane and peptidoglycan The peptidoglycan of a gram negative cell lies in sandwiched in the periplasmic space between the inner and outer membrane The peptidoglycan of gram positive cells is the outermost layer |
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What are the components of a gram negative cell starting from the membrane outward? |
Cytoplasmic membrane Periplasm Peptidoglycan Periplasm Lipopolysaccharide outer membrane |
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What are the component of a phospholipid bilayer? |
Fatty acids Glycerol Phosphate |
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What are the major chemical components of the cytoplasmic membrane |
Phospholipid bilayer Integral membrane protein Membrane strengthening agents |
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What are the 2 membrane strengthening agents mentioned in class? In what organisms do we find these? |
1) Sterols in eukaryotes and archaea's methanogens 2) Hopanoids in bacteria which are cholesterol analogs but are structurally different |
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How does the cell membrane of bacteria and eukarya differ from archaeal membranes? |
-Bacteria and Eukarya form bilayers with glycerol being bound to fatty acids via and ester -Archaea form monolayers or bilayers with glycerol ether bound to isoprene polymers |
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Describe the archaeal monolayer. What is the benefit of this? |
The glycerol of the inner leaflet of the membrane is directly bound to the glycerol of the outter leaflet of the membrane by biphytanyl. The ether links allow for greater rigidity/strength and allows for survival in extreme conditions |
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What are the 3 functions of the cytoplasmic membrane? |
1) Permeability barrier 2) Protein anchor 3) Energy conservation |
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What are the 3 types of membrane transport systems? |
1) Simple transport 2) Group translocation 3) ABC (ATP-binding cassette) systems |
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What are the 2 protein translocase system utilized in gram negative cells? |
SecYEG and Type 3 secretion |
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What are the 3 major components of peptidoglycan? |
1) Glycan backbone strand 2) Tetrapeptide side chain 3) Cross bridges |
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Describe binding of the glycan backbone |
N-acetylglucosamine(NAG) and N-acetylmuramicacid (NAM) are linked to each other by Beta-1,4 linkage in an unbranched manner |
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Describe peptidoglycans tetrapeptide side chain |
Four amino-acids in the sequence: L-alanine, D-glutamic acid, L-lysine, D-alanine. Each NAM of glycan strand is linked to four amino acid by peptide bond. |
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Describe peptidoglycans cross-linking/interbridge |
When two adjacent tetrapeptide side chain are linked to each other by a glycan molecule called as cross linkage.The carboxyl group of fourth amino aid D-alanine of side chain is linked to amino group third amino acid L-lysin of second tetrapeptide side chain.The linkage of carboxyl group and amino group is formed by five glycan (pentaglycan) molecules so called as cross bridge. |
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What component of the peptidoglycan cell wall is what allows us to differentiate gram-negative from gram-positive cells? |
The posession of a pentaglycan interbridge |
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What are teichoic acids? Where do we find them? What do they do? |
Acidic polysaccharides containing glycerophosphate or ribitol phosphate groups. Found only in gram positive bacteria, and imparts negative charge to gram positive bacteria in order to maybe aid ion transport |
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Penecillin is a beta-lactam antiobiotic. It works by inhibiting the ______ reaction by interfering with the cross-linkage of D-____ residues. This is not harmful to humans because D-____ is only found in bacterial cell walls, not outs |
transpeptidation reaction by interfering with the cross-linking of D-alanine residues. D-alanine is only found in bacterial cell walls |
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Describe the cell walls of archaea |
1) Assembled from surface-layer proteins called S-layers in combination with polysaccharides 2) Or can have a peptidoglycan homology called Pseduomurein which is similar but contains alternating repeats of N-acetylglucosame and N-acetyltalosaminuronic acid |
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Lipopolysaccharide aka endotoxin is found only in gram ____ bacteria. It replaces the ____ leaf of the lipid bilayer and is composed of 3 components. What are these components? |
Only in gram-negative bacteria and replaces outer leaf of the lipid bilayer. It's made up of: 1) Lipid A- anchor 2) Core polysaccharide 3) O-polysaccharide antigen side chain |
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What is gram-negative septesemia? What is the most sensitive test we have to detect the presense of LPS? |
Too much LPS is gram-negative septesemia and the blood of a horse shoe crab is the most sensitive test we have as it'll coagulate in the presense of LPS |
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How are larger molecules especially proteins secreted into the periplasm through the inner membrane? What is the fate of these molecules? |
Translocases They are not permeable through the outer membrane and thus are sequestered in the periplasm |
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Transcription and translation can be temporally co-linear in _____ |
Prokaryotes
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What is flagella composed of? |
Flagellin
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Compare the length of the tail to the cell that holds it |
Tail is much longer than the cell |
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When would a cell lose its flagellum? What does this tell us about flagella expression? |
When bacteria incorporate into a biofilm they can lose their flagellus, thus flagellar expression is envrionmentally dependent |
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What are the 3 types of flagellar arangement? What do they mean? |
1) Peritrichous (originating all around the cell) 2) Polar (originating at 1 end, can only be mono or bipolar but no more) 3) Lophotrichous (flagella all arise from a singular point) |
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What structure anchors the flagella via van der waals interactions and also utilizes the PMF to enable rotation of the hook. Describe proton flow through this body. |
The hook and basal body anchors the flagella. Since periplasmic face of the cytoplasmic membrane is positively charged, protons flow from periplasmic space into the cell membrane |
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How does the basal body of a gram-negative cel differ form that of a gram-positive cell? |
Gram negative has 4 rings instead of just 2 as in gram positive |
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Flagella can only move forward. ____ rotation makes the flagella work together to go forward, whereas ___ rotation causes the flagella to splay out from one another to allow for redirection |
CCW rotation makes the falgella work together whereas CW rotation causes them to splay |
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What is the random biased walk |
Distance to attractant is directly proportional to the length of the run and indirectly proportional to the frequency of tumbles |
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What are the 2 forms of light based locomotion? How do they work and how do they differ? |
Different wavelengths of light can alter the CW or CCW rotation of a flagella Scotophobotaxis - Movement away from darkness, thus regulated by lack of photons Phototaxis - Movement towards light, thus regulated by concentration of photos |
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Fimbriae and Pili are similar cell surface structures. What do they have in common? How do they differ? What are their roles? |
Both are tubular proteins. Fimbriae are not active and function passively such as sticking to surface. Pili engage in active roles such as conjugation, motility, and export. Pili are longer but fewer in number. Pili are the whiskeys and Fimbriae are the fur |
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How do we know that fimbriae are environmentally dependent? |
Different fimbriae are produced when attaching to the colon vs to the lungs |
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What is considered the most temporary of appendages that bacteria have? |
Pili!
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Flagella, Pili, and Fimbriae all assemble in a similar manner. How do they do it? |
All of these tubular proteins are hollow in the center. Protein precursors travel through the filaments and assemble at the top, growing from the tip outward |
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Bacteria frequenly produce a slime capsule to surround themselves. What is it made of? |
Polysaccharides, glycoproteins, and glycolipids. |
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What is the function of capsule/slime layers? |
They serve to protect the cell from phagocytosis, desiccation, chemical attach, and physical disruption |
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How do we visualize a bacterial capsule with a stain? |
India ink staining: the capsule appears as a clear halo around the bacterium as the ink can't penetrate the capsule |
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What is the glycocalyx? How does this differ from a capsule? How does india ink interact with this? |
It is the slime layer that is easily deformable unlike a capsule that is generally more rigid. India ink can indeed penetrate the glycocalyx |
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What is the name of the lipid storage polymer that is often used as a nutrient source when food becomes scarce? |
Poly-Beta-Hydroxybutyric acid (PHB) |
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What is the storage polymer of phosphate? |
Polyphosphate |
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What is the function of a gas vesicle inclusion? What is it made of?
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Small gas-filled structures made of protein that confer buoyancy to cells
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What are the 4 components of endospore structure? |
Exospore - outer protein coat Spore coat - layers of protein Cortex - Loosely arranged peptidoglycan Core - Cell wall, cytoplasmic membrane, cytoplasm, nucleoid, etc |
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How does the cytoplasm of an endospore differ from that or a vegetative cell? |
Cytoplasm is highly dessicated |
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What are the 3 properties of the core discussed in lecture? |
High in dipicolinic acid Highly dehydrated (only 10-30% of original water concentration) Presence of small acid soluble spore proteins (SASPs) |
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How does calcium interact with dipicolinic acid? |
Dipicolinic acid has 2 anionic carboxy ends which coordinate to the Ca2+ ion to cross link |
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What is the function of dipicolinic acid? |
It is a source of nutrition for the cell once it grows out |
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What is the function of SASPs? |
Small acid soluble spore protein protect DNA from radiation and heat and provide a source of food for outgrowth |
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How do we stimulate endospore formation? |
Lack of nutrients or other envrionmental stimuli |
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What happens during the outgrowth (germination) stage of an endospore? |
Loss of dipicolinic acid Metabolism of SASPs Production of DNA, RNA, and Proteins Rehydration Breaking of spore coat |
