24. The optimal temperature for most human pathogens might be expected to range

Question

24. The optimal temperature for most human pathogens might be expected to range from 35-40°C. B. 20-45°C. C. 15-25°C. D. 93-98.6°C. 25. True or False? Switching from high dry objective to oil immersion it is advisable to place a drop of oil on the slide and reduce the light by closing down the diaphragm. 26. True or false? The coarse adjustment knob can be used to adjust the focus when using the oil immersion lens. 27. True or False? Once focus is achieved at high dry magnification it is advisable to lower the stage when rotating to oil immersion lens to avoid striking the slide. 28. Staining is necessary to visualize cells using the light microscope. Which of the following use of the light microscope can be done without cell staining? A. Phase contrast. B. Dark field. C. Bright field. D. Fluorescent. E. Both A and B 29. The optimum pH for growth of most species of bacteria is A. pH 5. B pH 7 C. pH 9. D. pH 6 30. Which of the following are likely to be more sensitive to penicillin? A. Gram negative bacteria. 3. Acid fast bacteria. . Gram positive bacteria. Bacteria endospores. Vegetative fungi . Which of the following will be better observed of a bacterial cell using phase contrast microscopy Cell wall structure. Bacterial cell content. Motility of bacterial cells. acterial spores.

Explanation / Answer

24. Depending on the temperature range for survival and metabolism of microorganisms, they are categorized into mesophiles, psychrophiles and thermophiles. Mesophiles are organisms that can grow in the temperature range of 200C to 450C. The pathogens living in human body such as E. coli, Salmonella, Staphylococcus aureus ect are mesophilic. This is because their optimum temperature is near to human body temperature of 370C. Therefore, option A is correct. Psychrophiles live temperatures below 200C and thermophiles at temperatures of 80 - 1000C.

25. The given statement is false. This is because oil is placed on slide to view image clearly with highest possible resolution. Theuse of oil directs high amounts of light on object. The contrast can be increased by closing down the condenser diaphragm to allow less light pass through but it msay decrease the resolution of image.

26. The given statement is false. The dry objectives are adjusted with coarse knob and then fine tuning knob is used to view the image.In oil immersion lens fine focusing knob is used to view the image clearly.

27. The given statement is false.Once the focus is acheived with dry magnification, the objective lens is adjusted when the oil is placed on the slide but the stage is not lowered. Lowering of the stage may cause deviation of light beam and the resolution of objective may be disturbed.

Related Questions

Navigate

• Browse (All)
• Browse 2
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.