11. What type of staining is most useful for studying the morphology of bacteria
ID: 217579 • Letter: 1
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11. What type of staining is most useful for studying the morphology of bacterial cells and characterizing some of the external structures such as the capsule? a. staining b. staining c. Acid fast staining d. Negative staining 12. Examples of basic dyes used in the Microbiology lab are a. Methylene blue b. Crystal violet c. Safranin the a. Dorner method 13. Two methods available for Microbiologists for obtaining pure d. All of the above method cultures are the pour plate method and b. Gram stain c. Streak plate d. Inoculating method 14. A medium such as EMB (Eosin methylene blue) that llows certain bacteria to grow but inhibis others from growing is an example of a medium. b. Definedc. Selective d. minimal 15. To destroy all forms of life including endospores, all media is sterilized using a. Dry heat b. Radiation exposure for 30 minutes c. A pressure cooker d. Exposure for 15-30 minutes to steam under pressure (15psi) 16. An organism such as is classified as gram negative. a. E. coli b. S aureus c.P. vulgaris d. Both a and c are correct 17. Plates should be inverted during incubation to avoid e. The buildup of condensation on the medium d. All of the above a. Contamination b. Transformation of bacterial cells 18. The purpose of heat fixing a smear is to a. Adhere the cells to the slide e. Kill the cells d. Both a and b are correct b. Preserve their structural integrity 19. Gram staining is an example of a. Acid fast staining b. Acid staining c. Differential staining d. All of the above 20. Which of the following statement are true regarding gram positive bacteria a. Cell wan has a thin layer of peptidoglycan layer has a thick peptidoglycan layer a. Cell c. The LPS layer is thick 4. All of the above are true of gram positive bacteria 21. After ethanol treatment, an organism such as E. coli can be visualized a. Only by counterstaining with crystal violet c. Only by the addition of lodine b.Only by counterstaining with safranin d. All of the above 22. In Gram staining the primary stain used is Methylene blue b·Crystal violete. Safranin d, Malachite greenExplanation / Answer
11.Negative staining is useful for studying the morphology of bacterial cells and characterizing some of the external struvtures such as capaule.
12. All of the above.
13. Streak plate method.
14. EMB is a selective media for gram negative bacteria. EMB contains dyes that are toxic to gram positive bacteria and hence are selectively allowing gram negative bacteria to grow.
15. Exposure for 15-30 minutes to steam under presaure. This is done using Autoclave machine.
16. Both a and C ... i.e E.coli and p. vulgaris are gram negative bacteria. it is identified using gram stain. Gram negative bacteria does not retain the Crystal violet colour and appears red or pink under microscope.
17. plates are inverted so as to avoid the buildup of condensation on the medium so that it does not drip on the plate and hinder microbial growths.
18. Both a nad b are correct. i.e Heat fixing kills the cells and adhere the cells to the slide also it allows the cells to more readily take up the stain.
19. It is a differential staining and differentiate bacteria into 2 groups gram positive and gram negative.
20.Cell wall has a thick peptidoglycan layer.
21.only by counter staining with safranin.
22.Crystal violet is the primary stain used in gram staining.
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