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30 Cards in this Set
- Front
- Back
Gram-positive organisms absorb ____a____ and therefore appear to be colored ___b___.
Gram-negative organisms appear ___c___ because of the counter-stain __d___. |
a. crystal-violet
b. blue c. red d. safranin |
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Both gram-positive and gram-negative organisms have an extra cytoplasmic layer called the cell wall, or _______a______.
The amino-acid chains of the peptidoglycan covalently bind to other amino acids from neighboring chains, with the help of an enzyme called _____b____. |
a. peptidoglycan
b. transpeptidase |
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How does penicillin work?
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It binds to and inhibits the transpeptidase enzyme (also called "penicillin binding protein") that catalyzes the formation of cell wall linkages.
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What polysaccharide present in the gram-positive cell wall acts as an antigenic determinant and is thus important for serologic identification of many gram-positive species?
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Teichoic acid
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Do bacterial cytoplasmic membranes contain cholesterol or other sterols?
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No
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Gram-negative bacteria have a ___a____ space between the cytoplasmic membrane and the peptidoglycan layer, which is very __b___.
What is the space filled with? |
a. periplasmic
b. thin c. gel with proteins and enzymes |
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Does the thin peptidoglycan layer of gram-negative bacteria contain techoic acid?
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Nope.
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What is the important lipoprotein present in gram-negative peptidoglycan layers? Why is it important?
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Murein lipoprotein. It is important because it extends outward to bind the unique third outer membrane.
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What is unique about the outer third membrane of gram-negative bacteria?
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It contains lipopolysaccharide.
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What carbohydrate chains are antigenic determinants in gram (-)?
Where are they found? |
O-specific side chains, O-antigen
Found in the outermost layer of LPS |
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What is the center of LPS composed of?
What makes up the interior layer of LPS? What is another name for this substance? |
1. water soluble core polysaccharide
2. Lipid A, aka gram (-) ENDOTOXIN |
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Name 3 possible sequelae of gram (-) bacterial lysis in the human
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fever, diarrhea, and possible fatal endotoxic shock (septic shock)
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What class of gram organisms are vulnerable to lysozyme and penicillin attack?
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Gram (+) are vulnerable, because their thickly meshed peptidoglycan layer does not block diffusion of low molecular weight compounds.
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What are the four major bacterial shapes? Name one example of each.
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1. Cocci: strep, staph, neisseria (diplococci)
2. Bacilli/rods: listeria, e.coli (and most gram neg) 3. Spiral forms: treponema 4. Pleomorphic: chlamydia, rickettsiae |
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What are the 6 classic gram (+) bugs?
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1. streptococcus (strips of cocci)
2. staphylococcus (clusters of cocci) 3. bacillus (bacillus with spores) 4. clostridium (bacillus with spores) 5. corynebacterium (bacillus without spores) 6. listeria (bacillus without spores) |
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what is unique about LISTERIA as a gram (+) organism?
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Listeria is gram (+) but HAS endotoxin!
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What is the only group of gram (-) cocci?
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Neisseria (kissing coffeebeans diplococci)
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What is the best way to stain mycobacteria?
Name two diseases caused by mycobacteria |
acid-fast stain.
tuberculosis and leprosy. |
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what is the best way to visualize spirochetes?
what STD is caused by a spirochete? |
darkfield microscopy. spirochetes are tiny gram (-) bacteria that are too small to be seen with the light microscope.
syphilis, caused by Treponema pallidum |
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what group of bacteria are neither gram (+) nor gram (-)? why?
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Mycoplasma don't have a cell wall to hold on to any dye.
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Where can you usually find antibiotic resistant genes in bacteria?
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In PLASMIDS, smaller adjacent circles of double-stranded DNA.
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How do erythromycin and tetracycline act like magic bullets?
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They INHIBIT PROTEIN SYNTHESIS preferentially at the bacterial RIBOSOMAL subunits while leaving the animal ribosomes alone.
This is possible beacuse procaryotes have smaller, different ribosomes than eucaryotes. |
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What 3 enzymes can bacteria possess to break down reactive oxygen products?
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1. CATALASE: breaks down H2O2
2. PERODIDASE: breaks down H2O2 3. SUPEROXIDE DISMUTASE: breaks down superoxide radical |
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What enzymes do OBLIGATE AEROBES possess to help defend themselves?
Name 3 obligate aerobes |
They have catalase, peroxidase, and superoxide dismutase.
NOCARDIA and bacillus cereus (gram pos) NEISSERIA, pseudomonas, bordetella, legionella, brucella (gram neg) MYCOBACTERIUM (acid-fast) |
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What two enzymes do FACULTATIVE ANAEROBES possess? Name 3 facultative anaerobes
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Catalase and Superoxide dismutase.
They are aerobic, but have the capacity to be anaerobic. 1. STAPH, Bacillus anthracis, corynebacteria, listeria, actinomyces (gram pos) 2. MOST Gram negative RODS 3. MYCOPLASMA |
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What enzyme allows microaerophilic bacteria to tolerate low amounts of oxygen?
Name 3 aerotolerant anaerobes |
SUPEROXIDE DISMUTASE (no catalase like facultative anaerobes)
1. STREP 2. SPIROCHETES (treponema, borrelia, letpospira) 3. CAMPYLOBACTER (gram neg) |
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Name two obligate anaerobes
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CLOSTRIDIUM, BACTEROIDES
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What are chemoheterotrophs and why are they important?
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All the medically important bacteria are CHEMOHETEROTROPHS, meaning they use chemical and organic compounds (like glucose) for energy.
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What is the most common fermentation pathway for the breakdown of glucose to pyruvate?
Why do we care about this in micro? |
EMBDEN-MEYERHOF pathway.
Following fermentation the pyruvate must broken down, and the different end products formed in this process can be used to classify bacteria. |
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Why must obligate intracellular organisms always live in their host cell?
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Because they lack the metabolic machinery to utilize oxygen for ATP synthesis and must therefore steal their host's ATP.
Examples: CHLAMYDIA and RICKETTSIA (pleomorphic gram - ) |