The Gram stain is a widely used method in microbiology laboratories for identifying and classifying bacteria. It was developed in the late 1800s by Danish microbiologist Hans Christian Gram, who developed the technique as a way to differentiate between two major types of bacteria: gram-positive and gram-negative. Gram-positive bacteria have a thick peptidoglycan layer in their cell walls, which gives them a positive reaction to the Gram stain, while gram-negative bacteria have a thinner peptidoglycan layer and a negative reaction to the stain.
To perform a Gram stain, a sample of bacteria is first fixed to a microscope slide by heat or by adding a chemical fixative. The fixed sample is then covered with crystal violet, a purple dye that is taken up by both gram-positive and gram-negative bacteria. The slide is then rinsed with a decolorizing solution, which removes the crystal violet from the gram-negative bacteria, but leaves it in the gram-positive bacteria. The slide is then flooded with a counterstain called safranin, which stains the gram-negative bacteria red or pink.
Gram staining is an important technique in microbiology because it allows microbiologists to quickly and easily identify and classify bacteria. It is especially useful for identifying bacteria that are responsible for infections and for determining the appropriate course of treatment.
Multiple choice questions about the Gram stain might include:
Which of the following is NOT a step in the Gram stain procedure?
a) Fixing the bacterial sample to a microscope slide
b) Adding a counterstain
c) Incubating the slide for 24 hours
d) Covering the sample with crystal violet dye
Which of the following bacteria would be expected to have a positive reaction to the Gram stain?
a) Escherichia coli
b) Staphylococcus aureus
c) Pseudomonas aeruginosa
d) Bacillus subtilis
The Gram stain is useful for identifying bacteria because:
a) It allows microbiologists to determine the shape and size of the bacteria
b) It allows microbiologists to determine the metabolic activities of the bacteria
c) It allows microbiologists to differentiate between gram-positive and gram-negative bacteria
d) It allows microbiologists to determine the susceptibility of the bacteria to antibiotics
Answers:
c) Incubating the slide for 24 hours
b) Staphylococcus aureus
c) It allows microbiologists to differentiate between gram-positive and gram-negative bacteria
MCQs in Microscopy and Staining Techniques (Part II)
It must be safe because I drink this water all the time, but what could it be? The cells were grown in a gama-irradated single use container. Let us now wind the web of war And then follow the king to battle Gunn and Gondul can see there The blood-spattered shields that guarded the king. However, the duties of the mistresses were not limited to serving mead to visiting guests, but they were also expected to take part in warfare by manipulating weaving tools magically when their spouses were out in battle. However, all Gram positive will still be purple as they are able to retain the dye due to the structure of their cell wall. Answer: Wear protective gloves When you are doing the Gram stain, it is highly recommended that you wear gloves, as crystal violet, iodine and neutral red all stain your skin. Gram-negative bacteria have lesser amount of peptidoglycan layer and on treatment with alcohol it loses the purple-violet colour, are counterstained by safranin and hence appears red. I tried googling it but am overwhelmed by the bacteria answers and could not find anything about insect cells.
Bacteria And Gram Staining list of mcq quiz questions Page
Bacillus subtilis Answer: B Clarification: Eschericia coli is an example of Gram-negative bacteria. Upon further testing, I was unable to figure out what specific bacteria I was seeing. As part of a prac course in microbiology we've had to isolate colonies from cultures of bacteria from lettuce leaves and apply some basic identification tests. Which of the following is not a natural stain a Brazilin b Carmine c Safranine d Hematoxylin 2. Crystal violet, safranin, alcohol, iodine solution D. With swords we will weave this web of battle. The optimum temperature for an organism is the one at which A.
Which of the following is commonly used in a Hematoxyline b Acetocarmine c Crystal violet 3. The colony in question had rod morphology, was motile and reacted very strongly to both catalase and oxidase tests, unfortunately the sealed bags we used to test for anaerobic growth didn't work. Which of the staining technique helps in demonstrating spore structure in bacteria as well as free spores? Which of the following is a common nuclear stain? Thanks for playing, and hope you learnt something. I'm curious if running a gram stain test on insect cells to test for contamination could give you a false positive from staining the insect cells. In these halls there were magnificent feasts with ritualized meals, and the visiting chieftains can be likened with the einherjar, the fallen warriors who fought bravely and were served drinks by Valkyries. Which of the following contains polysaccharide? Let us now wind the web of war Where the warrior banners are forging forward Let his life not be taken; Only the Valkyries can choose the slain.
Which of the following are true for Gram-negative bacteria? An acidic dye is one in which the charge on the dye ion is negative and a basic dye is one in which the charge carried by the dye ion is positive. Crystal violet, alcohol, iodine solution, safranin B. . Streptococcus pyogens from Staphylococcus aureus d. What is the correct order of staining reagents in Gram-Staining? An encapsulated cell will reproduce to form colonies that appear a. Which of the following bacterial components is least likely to contain useful a. The bacterial envelope includes all of the following structures except a.
Neither Gram-positive nor Gram-negative Answer: A Clarification: Gram-positive bacteria retain the crystal violet and hence appear deep purple-violet colour as it has a higher content of the peptidoglycan layer. Iodine solution, crystal violet, alcohol, safranin Answer: B Clarification: Gram staining is a type of differential staining. Let us advance and wade through the ranks, Where friends of ours are exchanging blows. Which one of the following organisms is least likely to cause this illness? The cell wall type that is most vulnerable to the action of penicillin is a. When flagella are located around the entire bacterial cell, the arrangement is called a. Although, a stain will come off within a few hours, or by the next day at the latest.
Which bacteria appears purple-violet colour after staining? Others are all examples of Gram-positive bacteria. I had one colony that grew on MacConkey agar no lactose fermentation , but appeared to be gram positive after staining. Which of the following is a cytoplasmic stain a Eosin b Crystal violet c Carmine d Orcein 6. Carmine is obtained from a Plants b Fungus c Insects d Bacteria 5. Gram-positive bacteria are usually more susceptible to? The dye eosinate of methylene blue belongs to which group? A-initial stationary, b, c, d have the maximum amount of accumulated waste products? A slippery outer covering in some bacteria that protects them from phagocytosis by host cells is A. Staphylococcus aureus from Staphylococcus epidermidis c. Oxazine dye Answer: C Clarification: A neutral dye is a complex salt of a dye acid with a dye base so eosinate of methylene blue is an example of a neutral dye.
Most human pathogens prefer temperatures near that of the human body. Which of the following is good for staining proteins? Differences between eukaryotic and prokaryotic cells include all of the following except a. The web of man grey as armor Is now being woven; the Valkyries Will cross it with a crimson weft. Flagella stain Answer: B Clarification: There are numerous other staining techniques designed to identify some particular feature of cell structure or composition. A shiny, sticky colony of Streptococcus pneumoniae is likely to be A.
250+ TOP MCQs on Microorganisms Microscopic Examination
Gram negative cell wall b. A bacterial cell wall does all of the following except a. Gram-negative bacteria are more susceptible to other antibiotics like streptomycin. These cells subsequently take on the color of the safranin counterstain. I'm doing a project that's due tomorrow, hehe and studied water from several locations well-water from the sink, bottled water, and fridge-filtered.
