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Microbiology Lab UTA - Final Exam | Quizzes with Answers Verified 100% Correct
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Microbiology Lab UTA - Final Exam | Quizzes with Answers Verified 100% Correct
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Microbiology Lab UTA - Final Exam | Quizzeswith Answers Verified 100% Correct
Why gram stain - ✔✔Cells have same refractive index as water, we use light microscopes to
view them, stain makes the cells and internal structures more visible.
Gram positive cells - ✔✔have thicker peptidoglycan layer and stain purple when the teichoic
acid crosslinks to trap the stain.
Gram negative cells - ✔✔have a thinner peptidoglycan layer and have a LPS which is porous
so it doesn't retain the primary purple stain.
Gram Stain acronym - ✔✔Can I apply stain
Steps of gram stain - ✔✔1. prepare and heat fix the stain. 2. Apply crystal violet wait 1 min.
rinse w/Di. 2. Apply Gram;s Iodine- 1 min. rinse, 3. Apply ethanol 20 sec. wash di, 4. Apply
Safrinin 1 min rinse. blot and observe.
Alcohol/acetone mixture that dehydrates the cell, shrinking the cell wall. - ✔✔What are
decolorizers composed of and what do they do?
Coccus - ✔✔What shape are Gram (+) cells?
False - ✔✔Old cultures can lead to _____ Gram (-) results
Pyrogenic - ✔✔LPS layer is _____ and releases endotoxins.
,Lipid A (endotoxins), core polysaccharide, O-antigen (hydrophobic polysaccharide) - ✔✔LPS
composition
Bacillus - ✔✔What shape are Gram (-) cells?
Endospore - ✔✔Dormant form of bacteria
Allow the bacteria to survive environmental conditions that are not suitable for growth.
Highly Resistant to heat, radiation, acids, many chemicals (like disinfectants) because of protein
coat!!
Resistance due to keratinous outer covering. HEAT MUST BE APPLIED IN ORDER TO STAIN.
keratin - ✔✔Its thick protein coat of________________forms a protective barrier around the
endospore, which gives it resistance
Schaeffer-Fulton - ✔✔We use the _____________________method to stain the endospores
from Bacillus subtilis.
layers of the endospore - ✔✔Exosporium, spore coat, outer membrane, cortex, inter
membrane, spore cell
Centrally, Terminally (end), Sub-Terminally (middle) - ✔✔Where can endospores be located
within a cell?
Malachite green and safranin are applied. The ENDOSPORE IS STAINED GREEN and the rest of
the cell is stained pink. - ✔✔Endospore Staining Procedure
Pure cultures - ✔✔What is hopefully accomplished by streaking your sample on an agar
plate?
, Colony Forming Unit (CFU) - ✔✔Correct term for a colony
mixed populations - ✔✔In the environment, bacterial are ________ ____________.
Streak plate - ✔✔how to get a pure culture
What are capsules used for? - ✔✔Can help mediate adherence to host cells (initiating
infection)
Increase virulence of some microbes (protect bacteria from phagocytosis by eukaryotic cells)
Protect cells against drying/desiccation
Vaccine development via capsular polysaccharides
Capsule / Glycocalyx - ✔✔Thick, mucoid polysaccharide layer surrounding all bacterial cells.
Prevents desiccation, guards against the host immune response, and aids in adhering to host
cells.
No - the cell will shrink and the capsule will become distorted - ✔✔Can you heat-fix a
capsule?
Capsules resist stains, so basic crystal violet is applied to stain the interior of the cell while
acidic India Ink stains the background. The capsule appears white. - ✔✔Capsule Staining
Autoclaving removes the free oxygen in the media. As the agar cools, oxygen diffuses and
creates an OXYGEN CONCENTRATION GRADIENT ranging from aerobic to anaerobic. -
✔✔Why is media sterilized using the autoclave?
Fluid Thioglycollate Medium (FTM) - ✔✔Media testing the oxygen requirements of an
organism. Contains casein, sodium thioglycollate, and L-cystine.
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