BIO 420 – Laboratory Questions For Final Examination 2024 Approved Questions and Correct Answers Graded A+ Latest 2024 Update

BIO 420 – Laboratory Questions For Final Examination 2024 Approved Questions and Correct Answers Graded A+ Latest 2024 Update 60 questions Chapter 2 1. [CH-02-05] How is human immunodeficiency virus (HIV) resistant to disinfectants and antiseptics? Explain why. – HIV is enveloped virus and, therefore, it is highly sensitive to disinfectants and antiseptics. 2. [CH-02-07] What is difference between antiseptics and disinfectants? – Both antiseptics and disinfectants may kill microbes. However, disinfectants are harsh and cannot be used on human skin and their use is limited to unanimated objects, while antiseptics can be used on human skin. 3. [CH-02-08] What disinfectants are effective in killing bacterial spores? – Aldehydes, Bleach, Ethylene oxide, Paracetic acid 4. [CH-02-10] Which bacteria make up the normal flora of human skin? Name microbial genera. – Corynebacterium, Micrococcus, Staphylococcus, Propionibacterium -., Chapter 3 5. [CH-03-03] Explain the differences between magnification and resolving power of microscope – Magnification refers to the size of image with respect to the original object; Resolving power defines the size limit of visible objects and minimal distance between the objects to be seen separately. 6. [CH-03-05] Why do microscopists always start with the low magnification lens? – Low magnification lens has bigger viewing field and larger depth of focus than lenses with high magnification. As a result, it is easier to focus on specimen and scout it while using low magnification lens. 7. [CH-03-06] Compare the function of the brightness control with the iris diaphragm – Brightness control regulates the intensity of illumination emitted from light source (amount of light passing thought the specimen). Iris diaphragm regulates contrast of image and depth of focus. It also regulates the size of illuminated part of slide. 8. [CH-03-10] Why should closing the iris diaphragm in light microscope improve your ability to see more details in the resulting image? – Closing field iris diaphragm adjusts the size of the illuminated field of the slide and may reduce photo-bleaching of the slide. Closing aperture iris diaphragm adjust the amount of light passing through specimen and increases depth of focus. -., Chapters 4, 5, and 6 9. [CH-04-01] Why is it important to make the bacterial smear thin? – Making bacterial smear thin prevents the overcrowding of the slide and allows seeing the individual bacterial cells and their growth arrangements. 10. [CH-04-02] What is the purpose of heat-fixing the smear? – Heat-fixing kills bacterial cells and makes them stick to the slide. 11. [CH-04-03] Why is it important to dry the smear before heat fixing? – if smear is wet during heat-fixation, it will overheat and boil causing rupture of bacterial cells. The bacterial cells would also be washed away during staining procedure as they will not stick to the slide. 12. [CH-04-07] Describe morphology, cell grouping, oxygen and temperature requirements for Bacillus subtilis and Escherichia coli – Bacilli without growth arrangement, mesophilic obligate aerobe. Escherichia coli – bacillus with no cell grouping, that is mesophilic facultative anaerobe. 13. [CH-05-02] Which of the reagents used in the Gram stain is : • counter stain – Safranin; • decolorizer – 95% alcohol; • mordant – Iodine; • primary stain – Crystal violet. 14. [CH-05-05] In Gram stain, why does alcohol decolorize Gram-negative bacteria? – In Gram stain, primary stain binds to outer membrane of Gram-negative bacteria. Alcohol dissolves the outer membrane and thus removes primary stain from Gram-negative bacteria. 15. [CH-05-07] In Gram stain, if you stopped the procedure after decolorization how would the Gram-negative bacteria appear? How would the Gram-positive bacteria appear? – Gram-negative would be color-less; Gram-positive would be purple. 16. [CH-05-08] In Gram stain, if at the end of the procedure both the Gram-positive and Gram-negative bacteria appear red what is the most likely explanation? – The slide was overtreated with 95% and primary dye was removed from Gram-negative and Gram-positive bacteria. 17. [CH-06-02] Distinguish between cell membrane, cell wall, and capsule – Cell membrane is built of phospholipids and proteins and it serves as semipermeable boundary of the cell; Cell wall is located on top of cell membrane and is built of peptidoglycan. It serves as exoskeleton of the cell; Capsule is located on top of cell wall and built of polysaccharides. It has multiple functions – attachment to host, avoiding phagocytosis, prevention of water loss, depository of nutrients. 18. [CH-06-03] Capsulated strains of Streptococcus pneumoniae cause pneumonia in mice whereas non-capsulated strains of Streptococcus pneumoniae do not. Explain this phenomenon – Bacterial capsule interfere with phagocytosis enabling capsulated bacterial cells better survive attacks of phagocytic cells in animals and humans. 19. [CH-06-04] Give examples of vaccines that consist of capsular substance – Pneumococcal polysaccharide vaccine (PPSV) Pneumococcal conjugated vaccine against 7 or 13 antigens (PCV-7 or PCV-13); Meningococcal polysaccharide vaccine against 4 strains (MPSV-4) 20. [CH-06-05] What are the functions of capsule in bacterial cell? – The cell can use the capsule: 1) in attachment to the host; 2) to avoid the phagocytosis; 3) to reduce the loss of water when cell is outside of host; 4) as depository of nutrients. -., Chapters 7, and 8 21. [CH-07-01] For acid-fast stain, name the • Primary stain – Carbol fuchsine; • Decolorizer – Acid alcohol; • Counterstain – Methylene blue 22. [CH-07-04] Describe the morphology, cell grouping, oxygen and temperature requirements for Mycobacterium smegmatis – This is slender bacillus exhibiting “corded growth” due to its very hydrophobic acid-fast cell wall. It is mesophilic obligate aerobe. 23. [CH-07-05] Name the pathogenic species of acid-fast bacteria and the disease each species causes – Mycobacterium africanum, M. bovis, M. tuberculosis are causing tuberculosis; Mycobacterium leprae is causing leprosy or Hansen’s disease; Mycobacterium marinum may be occupational hazard to pet shop workers as it was isolated from fish and causes skin lesions; Mycobacterium avium is causing atypical mycobacterial infections in patients with late stages of HIV infection; Mycobacterium kansasii is causing chronic human pulmonary disease resembling tuberculosis and skin infections. 24. [CH-07-06] What substances in the wall of acid-fast bacteria account for their staining reaction? – mycolic acids that are C45-C90 substances (regular lipids are C18 substances). 25. [CH-08-03] List the pathogenic species of Bacillus and Clostridium with indication of the diseases they cause – Bacillus anthracis – anthrax; Clostridium tetani – tetanus; Clostridium botulinum – botulism; Clostridium perfringens – gas gangrene; Clostridium difficile – antibiotic- associated colitis. 26. [CH-08-04] What are dry heat treatment and autoclave conditions required to kill endospores? – Dry heat: 170OC for 2 hours or 200OC for 1,5 hours; Autoclaving: 121OC for 20 min at 15 psi. 27. [CH-08-07] What is the purpose of commercial sterilization of cans? What are the conditions for commercial sterilization of cans? – Purpose is to kill endospores of Clostridium botulinum. Conditions: 121OC for 3 min at 15 psi. 28.[CH-08-08] Broth prepared from yeast, meat or vegetative matter is sterilized by boiling. Broth from hay, however, frequently shows bacterial growth despite boiling. Explain why – Hay contains a lot of bacterial endospores that can easily survive boiling. -., Chapter 9 29. [CH-09-03] What is the advantage of growing bacteria on solid media? – Formation of bacterial colonies on solid media allows the isolation and maintenance of bacterial pure culture. 30. [CH-09-05] Describe bacterial morphology, oxygen and temperature requirements of Staphylococcus epidermidis – The cells of Staphylococcus epidermis are Gram positive cocci arranged in grape-like clusters. They are mesophilic facultative anaerobes. 31. [CH-09-09] Suppose you cough on plate and there is no growth after incubation. It is highly unlikely your cough was sterile. Suggest reasons why no growth was recovered on the plate – Bacteria may not grow for the following reasons: 1) some bacteria are fastidious (requiring special nutrients) that may be lacking in growth medium used; 2) wrong incubation temperature - bacteria from the throat are likely to prefer to grow at human body temperature. Lower or higher incubation temperature may inhibit their growth; 3) incubation time was not long enough for bacteria to grow and form colonies. 32. [CH-09-10] If you found the colony to be a mixture of organisms, what could you do to isolate them as pure cultures? – Prepare a new streak plate, so that they will grow in separate colonies. -., Chapters 10, and 11 33. [CH-10-01] Explain term “pure culture”. Why is it important to grow bacteria as pure cultures? – Pure culture is any bacterial culture that contain single microbial species. Pure culture allows to study the properties of bacterial species. Pure culture is also required for any use of bacteria in biotechnology. 34. [CH-10-06] If growth appears on unopened plates, what are some likely explanations? – 1) the medium was not properly sterilized. 2) the plates were not sterile; 3) medium was poured on to the plates in non-sterile conditions 35. [CH-10-09] What are the likely sources (reservoir) of microbes that grow best at 37OC? – human and animal bodies. 36. [CH-10-10] Colony size, color, and shape are critical of bacterial growth description. At least three other principal factors – not description of the organism itself – typically included when describing bacterial growth. What are they and why are they important? – culture medium used; atmospheric and temperature conditions; time of growth – all these factors affect the appearance of bacterial colonies. 37. [CH-11-03] Mesophiles bacteria have growth temperature range between +15OC to +42OC with optimal growth temperature around +30OC to +37OC. What is importance of these microbes to human health? – This group of bacteria is well suited to grow at temperature of human body. All human bacterial pathogens or opportunistic pathogens are mesophiles. 38. [CH-11-05] Compare obligate aerobes, facultative anaerobes, obligate anaerobes, microaerophiles and aerotolerant anaerobes. Give example for each microbial group – Obligate aerobes grow only in the presence of oxygen. These bacteria produce enzymes required to neutralize the toxic forms of oxygen formed during cellular respiration (Mycobacterium, Bordetella, Neisseria). Facultative anaerobes grow better in the presence of oxygen. However, they also can grow in the absence of oxygen as they can do fermentation (Escherichia, Lactobacillus, Staphylococcus). Obligate anaerobes can grow only in the absence of oxygen as it is toxic to them due to lack of enzymes required for neutralization of toxic forms of oxygen. Still, these microbes can do anaerobic cellular respiration (Clostridium). Microaerophilic bacteria (like Helicobacter pylori) require low oxygen concentrations (2-10%) for their growth. Higher oxygen concentrations would kill microaerophilic bacteria as microbes are producing catalase and superoxide dismutase in low quantities (Helicobacter). Aerotolerant anaerobes (like Streptococcus species) are growing equally well in the presence or absence of oxygen as these microbes are lacking