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32 Cards in this Set
- Front
- Back
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Name major differences between pro and eukaryotic cells. |
Bacterial cells: -no nuclear membrane -one chromosome -reproduce by binary fission -no membrane bound organelles -ribsomes 70S as opposed to 80S in human -respiratory electron transport occurs in cell membrane -cell wall w/ peptidoglycan (except mycoplasma) - cell membrane does not have sterols (except mycoplasma) |
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Why are the differences in eu and prokaryotic cells important? |
Can be targeted as sites of anti-bacterial therapy |
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Two parts of bacteria name are ______ and _____. |
genus and species. |
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How are strains of particular bacterial species identified? |
subtyping: biotyping, serotyping, phage typing, genotypning, antimicrobial sensitivity testing. |
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How are bacterial colonies phenotypically classified? |
pigmented/not pigmented, rough or smooth, glistening or dull, flat or raised, distinguishing odors.
When inoculated on a plate containing blood cells, they are characterized as alpha, beta or gamma hemolytic. |
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Define Alpha-hemolytic. |
an incomplete hemolysis of red cells resulting in greenish-brown zone surrounding/under colonies. |
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Beta-hemolysis? |
complete hemolysis of red blood cells resulting in clear or colorless zones surrounding colony |
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Gamma hemolytic? |
non hemolytic |
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How are cells phenotypically identified microscopically? |
-gram positive/negative/variable -shape: cocci, bacilli, spiral, pleomorphic -arrangement: clusters, chains, pairs -biotyping: based on presence/absence of specific biochemical markers: ferment sugars, production of end products, relationship to O2. -serotyping/immunoassay: detect unique antigens, good for difficult to grow organisms -antibiograms: susceptibility -phage typing: susceptibility |
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What is the advantage to genotypic classification? |
-advantages: specificity and ability to detect organisms that cannot be cultured.
techniques: GC content, DNA hybridization, sequence analysis
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What is the process of Gram-staining? |
application of crystal violet, application of iodine, alcohol wash, application of safranin.
gram positive appear purple while negative appear pink. there are many important bacteria that do not stain so it is essential to notify the lab of what you suspect. |
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What is the function of the bacterial cell wall in disease processes? |
polysaccharide components of cell walls are often antigens and used in lab identification. |
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How do cells walls of gram positive vs. gram negative bacteria differ? |
positive- thicker peptidoglycan, some with teichoic acid, no LPS, no periplasmic space, no outer membrane.
negative- thin peptidoglycan layer, no teichoic acids, has LPS, has periplasmic space, has an outer membrane. |
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What is the importance of the periplasmic space in gram negative bacteria? |
This is often the site hydrolytic enzymes, including beta-lactamases. |
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Why can't some bacteria be gram stained? |
too much lipid in cell wall (dye cannot penetrate), some bacteria too thin to see, lack of cell wall (very small bacteria), some are intracellular (within human cell). |
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LPS is an _______. How does this define it's antigenicity? |
endotoxin. It is released as membrane blebs when the cell lyses, as opposed to exotoxins, which are made and secreted.
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Describe the basic structure of peptidoglycan. |
alternating polysaccharide of n-acetylmuramic acid and n-acetylglucosamine molecules.
tetrapeptides of both D- and L- amino acids are attached to the muramic acid molecule. |
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How does lysozyme effect peptidoglycan layer of cell wall? |
cleaves the backbone breaking glycosyl bonds, weakening the wall, making it more susceptible to antibiotics.
"first hit"
In hypotonic solution, this weakening leads to cell swelling and lysis |
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T/F the peptidoglycan layer can activate TLRs via PAMPS. |
truth. can act as an endotoxin with similar effects to LPS, but much less potent. |
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What is the basic structure of LPS? |
composed of 3 units: -Lipid A- phospholipid responsible for toxic effects -A core polysaccharide of 5 sugars linked to lipid A -Outer polysaccharide consisting of 25 repeating units of 3-5 sugars; this antigen used for clinical identifaction
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What is the basic structure of teichoic acids and their role in pathogenesis? |
these are water soluble polymers of glycerol or ribitol linked to peptidoglycans in outer layer of Gram positive cell wall and extending from it.
Induce sepsis cause by certain gram-positives by activating similar pathways to LPS. |
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The _____ gives bacterial colonies a mucoid appearance. |
capsule. |
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Why is the bacterial capsule important (4)? |
-it's a virulence factor inhibiting phagocytosis -antibodies can be used against the capsule to ID bacteria (Quellung test) -Capsular polysaccharides important in eliciting protective antibodies as antigens in certain vaccines. -important in adherence to tissues and formation of biofilms |
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_______ are long filamentous appendages that propel bacteria towards attractants, and are composed of _______ in intertwined chains. |
flagella, flagellin (as repeating subunits) |
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The cytoplasmic membrane is responsible to what in prokaryotes? |
-electron transport chain -active transport of molecules -synthesis of cell wall precursors -signal transduction |
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T/F flagella most common in cocci. |
False, rods. |
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What is the function of pili? |
mediate attachment of bacteria to specific receptors on human cells, can be a virulence factor.
also mediate attachment to other bacteria. F pili function during conjugation (genes for their expression located on plasmids). |
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____ is the protein that makes up pili. |
pilin. LOL. |
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______ and _____ are the bacteria that produce spores. |
clostridium and bacillus. They form spores when nutrients are scarce. |
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What are the components of a spore? |
bacterial DNA, small amount of cytoplasm, cell membrane, peptidoglycan, a little water, and a thick, keratin like coat. |
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_______ is a calcium chelator only found in spores. |
dipicolnic acid. used to sequester calcium for enzymes. |
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Why do spores present a difficulty for medical procedures? |
spores are not killed by boiling; must be heated to approx 121C for 15 minutes to sterilize.
spores resistant to many chemicals and can survive for many years, even in soil.
antibiotics cannot penetrate spore coat.
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