MICROBIOLOGY CHAPTER 6 TEST BANK

The addition of which of the following to a culture medium will neutralize acids? A) Buffers B) Sugars C) PH D) Heat E) Carbon A- Buffers Salts and sugars work to preserve foods by creating a A) Depletion of nutrients. B) Hypotonic environment. C) Lower osmotic pressure. D) Hypertonic environment. E) Lower ph. D- Hypertonic environment The term facultative anaerobe refers to an organism that A) Doesn’t use oxygen but tolerates it. B) Is killed by oxygen. C) Uses oxygen or grows without oxygen. D) Requires less oxygen than is present in air. E) Prefers to grow without oxygen. C - Uses oxygen or grows without oxygen Which of the following is not a disadvantage of the standard plate count? A) Cells may form aggregates. B) Requires incubation time. C) Determines viable cells. D) Chemical and physical requirements are determined by media and incubation. E) None of the above. C- Determines viable cells Which of the following is not a disadvantage of the direct microscopic count? A) Some organisms are motile. B) Enumerates dead cells. C) No incubation time. D) Sample volume is unknown. E) Large number of cells is required. D- Sample volume is unknown Which of the following is not used to determine metabolic activity? A) Acid production from fermentation. B) CO 2 produced from the Krebs cycle. C) NO2- produced from the electron transport chain. D) Decreased dissolved oxygen. E) Turbidity. E - Turbidity Thirty-six colonies grew in nutrient agar from 1.0 ml of undiluted sample in a standard plate count. How many cells were in the original sample? A) 4 B) 9 C) 18 D) 36 E) 72 E- 72 Most bacteria grow best at pH A) 1. B) 5. C) 7. D) 9. E) 14. C- 7