5. Gram+ & Gram- Bacteria Flashcards
You are observing a specimen taken from the red, raised wound of a patient. Under the microscope, you see round cells clumped together resembling grapes. Name the bacteria (MG)
A. Bacillus
B. Staphylococcus
C. Streptococcus
D. Pallisades
B. Staphylococcus
Staphylo literally means grape bunch. The rest of bacteria are in the yellow table in the lecture (I don’t want to spoil other people’s questions)
Lipoteichoic acid protects bacteria from ____ and is only found in gram ____ bacteria (MG)
A. Heat; +
B. Lysis; +
C. Water; -
D. Endotoxins; -
B. Lysis; +
This is the most correct answer. Only found in gram positive cells and helps to protect from lysis when the tonicity of solution/environment is changed.
A man is looking at microorganism through a microscope and notices through testing that it stains red during a gram stain. What other characteristic is true of this microorganism?
A. It is Gram Positive
B. It has a thick peptidoglycan cell wall
C. Has a wall of teichoic acid
D. Iodine didn’t affect its coloring during staining
E. It has periplasm
RFA
Ans. E. Gram negative cells have periplasm, a space between their inner and out membranes
all the others are characteristics of Gram postive bacteria
D. Iodine would wash away the initial crystal violet stain allowing it to be stained by safranin
A man has a persistent cough and it is shown through testing that his antibodies are not able to phagocytize the cause of the infection which through testing is show to be Streptococcus pneumoniae. Why can’t the immune cells phagocytize this bacteria?
A. Peritrichous cells are not able to phagocytized
B. Gram negative cells can’t be phagocytized
C. The cells are endospores and are resistant
D. The cells possess a Glycocalyx inhibits phagocytosis
E. A very thick Gram positive protective cell wall
RFA
Ans. D The cell posses a Glycocalyx
A student is prepping a gram negative bacteria. She doesn’t use an adequate amount of ethanol during step 6. How will the bacteria appear?
A. Cells will be red in color B. Cells will be purple in color C. Cells will not adhere to the slide D. Cells will not die E. Cells will be counterstained
SZ
Ans. B
Cells will be purple in color
Step 6 is rinsing the slide with ethanol which decolorizes the cells. In a gram negative bacteria this step should rinse off the crystal violet stain if a proper amount is used. However, if the dye is not removed the cell will appear purple in color.
Which of the following numbers is the best for accurate counting of plated colonies following serial dilutions?
A. 150 B. 20 C. 2 D. 350 E. 400
SZ
Ans. A 150
30-300 colonies or 10^-4 are the best for accurate counting.
10^-1, 10^-2, 10^-3 result in confluent growth (too numerous to count)
10^-5 and 10^-6 result in too few to count.
After serial diluting a sample of E. Coli 3 times (1:10 ratios), You proceed to place a .02 ml of the diluted sample on growth agar. 24 hours pass and you observe the amount of CFUs to be 200. What was the original bacterial count?
FA
10,000,000 per ml
Diluting 3 times at a 1:10 ratio would end up with a total dilution of 10^-3
the formula i use is CFUs/(Volume of drop)*(Dilution) = Count/ml
200/(.02ml)*(10^-3) = 200/.00002 = 10,000,000/ml
Penicillin is a drug that disrupts the formation of the bacterial cell wall during growth. therefore it is most effective in the exponential phase of bacterial growth. Which of the following describes how penicillin preforms this task?
A. Prevents formation of 1-4 B-glycosidic bonds between the alternating NAG-NAMs
B. Prevents the Peptidoglycan cross links between the protein tails of NAMs
C. Prevents the bacteria from recieving biotin, thus causing it to undergo vitamin b7 deficency
D. Creating a whole within the cell wall, causing the cell to lysis due to osmotic forces
FA
B. Penicillin is a b-lactam antibiotic that disrupts the formation of the replicating bacteria by preventing the formation of the crosslinks that occur between each protein chain of the peptidoglycan wall. The protein chains only branch of NAM.
Which component of the Cell Membrane is high toxic and causes a “cytokine storm”?
A) Hopanoides
B) Mycolic Acid
C) Lipid A
D) Cord Factor
*bonus - Is it found in gram + or -? *
MM
Answer C - found in gram -
A - Provide rigidity
B - found in TB, Leprosy, and Nocardia. Stains Acid Fast
D- found in TB, gives serpentine formation
Ahmed is a very bored scientist and decides to look at his sperm under a microscope. He notices a single flagella. He thought back to a previously isolated microbe (1) which had multiple flagella at one end and another microbe which has flagella surrounding all sides of it (2) except the very front. What is the structure of the sperms flagella____, microbe (1) ____, and microbe (2)______?
MM
Sperm- Monotrichous
(1) - Lopotrichous
(2) - Peritrichous
Amphitrichous = 1 flagella at each end
