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19 Cards in this Set
- Front
- Back
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What are the four steps to Gram stain a specimen? What does being "Gram positive" or "Gram negative" mean?
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Prep by smearing hte ubstance to be stained (sputum, pus, etc.) onto a slide and then heat it to fix the bacteria onto the slide. Then the 4 steps are:
1. Pour on crystal violet stain (blue dye) and wait 60 seconds. 2. Wash off with water and flood with iodine solution. Wait 60 seconds. 3. Wash off with water and then "decolorize" with 95% alcohol. 4. Counterstain with safranin (red dye). Wait 30 seconds then wash off with water. Gram positive is if the specimen turns BLUE. Gram negative is if specimen turns RED (think red is negative). The crystal violet stain used for Gram staining is a large dye complex that is trapped in the thick, cross-linked gram-positive cell wall, resulting in the gram-positive blue stain. The outer lipid-containing cell membrane of the gram negative org is partially dissolved by alcohol, thus washing out the crystal violet and allowing the safranin counterstain to take. p.1 in Made Easy |
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The amino acid chains of the peptidoglycan (cell wall) layer of a bacteria covalently bind to other amino acids from neighboring chains. This results in a stable cross-linked structure. The enzyme that catalyzes the formation of this linkage is called _____________.
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Transpeptidase. Penicillin binds to and inhibits this enzyme. (Thus penicillin is only useful for Gram + bacteria since Gram - bacteria has that outer membrane layer.)
p. 1 in Made Easy p. 118 in First Aid |
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For each listed, state whether it is a feature of Gram + or Gram - bacteria.
1. Have teichoic acid 2. Have periplasmic space 3. Have thick peptidoglycan layer 4. Have an outer membrane 5. Have LPS 6. Have murein lipoprotein |
1. Have teichoic acid = Gram +
2. Have periplasmic space = Gram - 3. Have thick peptidoglycan layer = Gram + 4. Have an outer membrane = Gram - 5. Have LPS = Gram - 6. Have murein lipoprotein = Gram - p. 2 in Made Easy |
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What does the murein lipoprotein do in the Gram - bacteria?
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Murein liproprotein, unique to Gram - bacteria, originates from the peptidoglycan layer and extends outward to bind the unique third outer membrane in Gram - bacteria. The outermost layer of that outer membrane has LPS, which has an O-specific side chain, core polysaccharide and Lipid A (endotoxin)
p.3 in Made Easy |
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What are the 7 classic Gram + bacteria?
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3 are cocci-shaped: Staphylococcus, Streptococcus, Enterococcus
2 are spore-forming: Bacillus, Clostridium 2 are non-spore forming: Listeria, Corynebacterium p. 4 in Made Easy |
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Of the gram negative organisms (which is basically everyone else besides the 7 Gram + ones), there is
1. only 1 group of gram-negative cocci - name em! 2. only 1 group of spiral shaped organisms - name em! The rest of the gram negatives are rods or pleimorphs! |
1. Gram negative cocci = Neisseria (is a diplococcus- looks like 2 beans kissing)
2. Gram negative spirals = Spirochetes (which includes Treponema pallidum, which causes syphillis) The exceptiosn are mycobacteria which is weakly gram + but stains best with acid-fast stain (TB and leprosy). Spirochetes have a gram - wall but are too small and must be viewed with darkfield microscopy. Finally, mycoplasma do not have a cell wall. They have a simple cell membrane so they are neither Gram + nor Gram -. P. 5 in Made Easy |
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Prokaryotes have smaller ribosomes (70S) than animals (80S).
A. Bacterial ribosomes consist of two subunits. Nam em. B. Antibiotics such as erythromycin and tetracycline were developed to have specificity for which subunits, respectively? |
A. the two prokaryotic ribosome subunits are 50S and 30S.
B. Erythromycin works at the 50S site; Tetracycline works at the 30S site. p. 6 in Made Easy |
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What are the three enzymes that some bacteria possess to break down reactive oxygen products? Regarding the obligate aerobes, facultative anaerobes, microaerophilic and obligate anaerobes, list which enzymes are in each category.
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3 enzymes to break down reactive oxygen species are:
- CATALASE : breaks down hydrogen peroxide to water and oxygen - PEROXIDASE: also breaks down hydrogen peroxide - SUPEROXIDE DISMUTASE: breaks down superoxide radicals (O2-) to hydrogen peroxide and oxygen Obligate aerobes and facultative anaerobes have all of three enzymes. Microaerophilic only have the superoxide dismutase thus can tolerate just a bit of oxygen. Obligate anaerobes don't have any of those 3 enzymes and thus are intolerant of oxygen completely! |
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Regarding flagellum arrangement, bacteria can have polar flagellum (as with ________), many peritrichious flagella or all around the cell (as with _______ and _______ ) or no flagella as with ________.
A. Eschericihia coli B. roteus mirabilis C. Shigella D. Vibrio cholera |
polar flagellum = Virbio cholera
peritrichious = E. coli , Proteus mirabilis no flagella = shigella Made Easy, Ch.2 |
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Which group of bacteria have periplasmic flagella?
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Spirochetes
Made Easy, Ch.2 |
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Pili, also called __________, are straight filaments arising from the bacterial cell wall, making the bacterium look like a porcupine. These are much shorter than flagella and do not move. What do they usually serve as?
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Adherence factors called adhesins.
Ex. Neisseria gonorrhea's pili --> bind to cervical and buccal cells to cause gonorrhea E.coli and Campylobacter jejuni pili --> bind to intestinal epithelium causing diarrhea Bordatella pertussis pili --> bind to intestinal epithelium to ciliated respiratory cells and cause whooping cough Bacteria that do not produce these pili cannot grab hold of their victim; they lose their virulence and cannot infect the human. Made Easy, Ch.2 |
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Capsules are protective walls that surround the cell membranes of gram-positive and gram-negative bacteria. They are usually composed of [ amino acid residues / simple sugar residues ] exception being Bacillus anthracis which is composed of [ amino acid residues / simple sugar residues ].
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Capsules = simple sugar residues
Bacillus anthracis is unique = amino acid residues Made Easy, Ch.2 |
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What two important tests enable doctors to visualize CAPSULES under the microscope and aid in identifying bacteria?
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India ink stain : This in stain is not taken up by capsule, the capsule appears as a transparent halo around the cell. commonly used to ID fungus Cryptococcus.
Quellung reaction: Bacteria are mixed with antibodies that bind the capsule. When antibodies bind, the capsule swells with water, and this can be visualized microscopically. (side note: Quellung rxn is + w/ Strep pneumoniae) Made Easy, Ch.2 |
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What two genera of bacteria form endospores?
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aerobic Bacillus and anaerobic Clostridium
both are also Gram +. Made Easy, Ch.2 |
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A biofilm is an extracellular polysaccharide network, similar to the capsule polysaccharides, that forms a mechanical scaffold around bacteria. What bacteria often forms biofilms on intravascualr catheters and leaches out to cause bacteremia and catheter related sepsis?
A. Staph aureus B. Staph epidermidis C. Staph saprophyticus D. Strep agalactiae |
B. Staph epidermidis
The most effective way to cure an infection involving a prosthetic device is to remove the device. Made Easy, Ch.2 |
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Many bacteria are phagocytosed by the host's macrophages and neutrophils yet survive within these WBCs unharmed. These bacteria inhibit phagosome-lysosome fusion, thus escaping the host's deadly hydrogen peroxide and superoxide radicals. What 7 bacteria are these facultative intracellular orgs?
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- Listeria monocytogenes
- Salmonella typhi - Yersinia - Francisella tularensis - Brucella - Legionella - Mycobacterium Made Easy, Ch.2 |
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How do endotoxins differ from exotoxins?
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Endotoxins differ from exotoxins in that it is not a protein excreted from cells, but rather it is a normal part of the outer membrane that sort of sheds off, especially during lysis.
This, sometimes treating a patient who has a gram-negative infection with antibiotics can worse the patient's condition because all the bacteria are lysed, releasing large quantities of endotoxin. (Remember that endotoxin is Lipid A, which is on the outer cell membrane that only Gram NEGATIVE bacteria have.) Made Easy, Ch.2 |
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In sepsis, TNF triggers the release of the cytokine _______.
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IL-1, or interleukin 1, from macrophages and endothelial cells, which in turn triggers the release o other cytokines and prostaglandins.
Made Easy, Ch.2 |
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What are the four bacteria that produce exotoxins that increase the level of cAMP?
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think cAMP!
c = cholera (Vibrio cholera) A = anthrax (Bacillus anthracis) M = Montezuma's revenge (popular name for enterotoxigenic E.coli) P = pertussis (Bordatella pertussis) Made Easy, Ch.2 |
