Name of students
Admission No
Class
Total Marks / 45
Assignment 1
1. Explain the principle of positive staining.
(3 marks)
Positive staining is done by staining the cell walls of Gram-positive bacteria with crystal violet. The cell wall of Gram-positive bacteria is made up of a thick layer of peptidoglycan which undergoes dehydration during decolourisation causing the pores to shrink. This shrinkage of pores traps CV-I complex and stain the cell purple.
2. Using a flow chart, outline the process of gram staining.
(5 marks)
Flood the slide with crystal violet for 1 minute then rinse with water
Flood the slide with iodine for 1 minute then rinse with water
Flood the slide with solution of ethanol and acetone for 10 to 30 seconds then rinse with water
Flood the slide with safranin for 1 minute then rinse it with water
Blot dry the slide
3. What is the function of iodine when used in gram staining?
(2 marks)
Its function is to form large crystals with crystal violet so that they stick to the bacterial cell wall and are not washed away easily.
4. Attach photos on JPEG format showing a gram positive and gram negative bacterial sample showing their gram staining reaction. Give the name of the bacterial cells, shapes and arrangement.
(9 marks)
Bacillus cereus: Rod shaped and chain arrangement, Gram positive http://aapredbook.aappublications.org/content/1/SEC131/SEC143/F178.large.jpg Neisseria gonorrhoea: Coffee bean shaped and diplococcus arrangement, Gram negative http://upload.wikimedia.org/wikipedia/commons/2/2e/Gonococcal_urethritis_PHIL_4085_lores.jpg 5. Explain the principle of capsule staining using both a basic and acidic dye.
(5 marks)
Capsule staining with basic dye is basically to stain the bacterial cells within the capsule without staining the outer part. Capsule staining with acidic dye is to stain the background without it penetrating into the capsule.
6. Using a flow chart, outline the process of endospore staining.
(5 marks)
Prepare smear of the bacteria to be stained
Heat-fix the smear
Place a piece of filter paper over the smear
Saturate the paper with malachite green
Heat the slide to steaming for 5 minutes to drive the dye into the endospores
Remove the paper and wash the slide with distilled water to remove excess dye
Counterstain the smear with safranin which it will stain the vegetative cells red-pink
Wash the slide with distilled water and blot dry it
7. What will be the appearance of bacteria that possess endospore? Attach a JPEG photo each of cells with and without endospores after endospore staining.
(5 marks)
8. Name two genus of bacteria that possess endospore.
(2 marks)
Bacillus. Clostridium.
9. What is acid-fastness?
(2 marks)
Acid-fastness is a physical property of some bacteria which have resistance to decolourisation by acids during staining.
10. Using a flow chart, outline the process of acid-fast staining.
(5 marks)
Prepare smear of the bacteria to be stained
Heat-fix the smear
Apply carbol fuchsin to the heat-fixed smear
Heat the slide to steaming for 5 minutes to drive the dye into the cell
Wash the slide with distilled water
Treat the slide with acid-alcohol solution to decolourise both non acid-fast cells and background
Counterstain with methylene blue
Wash the slide with distilled water and blot dry it
Acid-fast bacteria will appear pink in colour while non-acid-fast bacteria will appear blue in colour
11. What is the possible reason why bacteria that exhibit acid-fastness stained poorly with gram stains?
(2 marks)
Bacteria that exhibit acid-fastness have high lipid content in their cell wall resulting in a waxy texture. As such, only a small amount of gram stains will be able to enter and stain the cell wall
You May Also Find These Documents Helpful
-
Specific bacterial morphologies noted in exercise one come from the spiral bacteria sample. The shape appears to be corkscrew in nature and vary in length throughout the sample slide. The length varies but the width seems to be uniform. The color most likely arises from the stain used to allow for better visualization of the organism. The Bacillus sample has no discernable morphology and appears as round ended, and cylindrical shaped in nature. The organisms have a black tint which is probably related to the type of statin used for visualization of the organism.…
- 588 Words
- 2 Pages
Good Essays -
Through the semester, you have used two bacteria that produce colorful colonies: one produce yellow colonies, another one pink. What are the names of these two bacteria? Are they Gram+ or Gram-?…
- 1237 Words
- 5 Pages
Powerful Essays -
B: On each examples bacterial morphologies are visible and easy identified. In the wet mount example with yeast, cocci is noted, while is hard to determine in cheek smears. Check smear and yeast smear contain cocci with direct staining. At direct staining plaque smear contain cocci and bacillus. Yeast with indirect staining contains cocci as well. On same picture bacteria are singled while on some pictures bacteria are in group and uneven clusters. Different type of stain plays role to differentiate the shape of bacteria.…
- 472 Words
- 2 Pages
Good Essays -
The following tables are each corresponding to either the Gram-positive sample or Gram-negative sample and include the tests utilized along with their results all in the order each test was performed. In section 10, Figures, there are some pictures corresponding to the stains performed. In Figure 1, the Gram-positive stain, you can clearly see the purple color and cocci morphology in grapelike clusters. Figure 2 is the Gram-negative stain with the safranin color and shows bacilli cellular morphology.…
- 1229 Words
- 5 Pages
Powerful Essays -
5Take the slide and using a rag with solvent on it, wipe it down and rub to remove any visible deposits of gunpowder residue and light markings from the cartridges. Wipe the surface of the slide with a cloth to remove fingerprints and body oil from handling. Use your finger to spread a light layer of slide grease on the surface of the slide groove. Set this aside for the moment.…
- 463 Words
- 2 Pages
Good Essays -
The Gram stain separates bacteria into two major groups: Gram positives that stain purple, and Gram negatives that stain pink or red.…
- 1967 Words
- 8 Pages
Better Essays -
9.) Be sure to note the morphology of the bacteria and whether it is gram-positive or negative.…
- 777 Words
- 4 Pages
Good Essays -
This test is performed to get a description of the make-up of the cell membrane of the bacteria. A gram positive bacteria will display a blue/violet pigmentation where a gram negative bacteria will display a pink/red pigmentation. This is due to the outer membrane of gram negative bacteria. My unknown bacteria displays a pink color hinting the presence of a gram negative bacteria.…
- 2236 Words
- 9 Pages
Better Essays -
The tests performed on the unknown bacteria cultures were all used to determine the identity of the bacteria. Each of the tests performed provided some key information about the bacteria in question and how it functions. Not all of the tests were performed on every culture, however, as some of the tests were used only for gram (+) or gram () bacteria, while others were even more specific and used only for cocci bacteria. The tests performed and what constitutes a positive and negative test are as follows.…
- 2145 Words
- 9 Pages
Better Essays -
To identify an unknown bacterial specimen using basic laboratory technique and biochemical tests. The unknown bacteria will be one of the following: Enterococcus faecalis, Staphylococcus saprophyticus, Escherichia coli, Enterobacter aerogenes, Proteus vulgaris, Salmonella [I assume typhimurium], or Shigella [either flexneri or sonnei, we used both in our lab during the semester].…
- 1149 Words
- 5 Pages
Good Essays -
7) Continue to reset the slides and continue testing until you have identified each bacterial species described in the Microbiology handbook, as well as one unknown species.…
- 720 Words
- 3 Pages
Good Essays -
Staining technique that divides bacteria into gram-negative or gram-positive based on retention of a violet dye…
- 1167 Words
- 5 Pages
Better Essays -
(8) Proceeding to decide whether or not to keep a minor in custody is a detention…
- 1360 Words
- 6 Pages
Good Essays -
The Stroop color–word task cannot be administered to children who are unable to read. However, our color–object Stroop task can. One hundred and sixty-eight children of 3½–6½ years (50% female; 24 children at each 6-month interval) were shown line drawings of familiar objects in a color that was congruent (e.g., an orange carrot), incongruent (e.g., a green carrot), or neutral (for objects having no canonical color [e.g., a red book]), and abstract shapes, each drawn in one of six colors. Half the children were asked to name the color in which each object was drawn, and half were to name each object. Children’s predominant tendency was to say what the object was; when instructed to do otherwise they were slower and less accurate. Children were faster and more accurate at naming the color of a stimulus when the form could not be named (abstract shape) than when it could, even if in its canonical color. The heightened interference to color-naming versus object-naming was not due to lack of familiarity with color names or group differences: Children in the color condition were as fast and accurate at naming the colors of abstract shapes as were children in the form condition at naming familiar objects.…
- 725 Words
- 3 Pages
Good Essays -
As I recall from earlier that semester, the first test that needed to be performed was the Gram stain. The Gram stain is a staining technique that aids in distinguishing cell wall characteristics and the cellular morphology. Bacteria will stain Gram positive, which is a purple color, or Gram negative, which is a pink color. Also, the Gram stain can help to identify the shape of the bacterium. The three basic shapes are cocci, bacilli and spirilli, which means that cocci are berry shaped, bacilli are rod shaped and spirilli are spiral shaped. My unknown bacteria stained purple which means that it is Gram-positive and was berry shaped meaning that the bacterium is cocci. These results have led me to the next step for me to master, the catalase test.…
- 749 Words
- 3 Pages
Good Essays