1. What is a pure culture? a) a culture plate that contains morphologically simi
ID: 69271 • Letter: 1
Question
1. What is a pure culture? a) a culture plate that contains morphologically similar but unrelated bacteria. b) a colony of widely diverse types of organisms. c) a group of similar organisms on a Petri dish. d) a culture that contains only one type of organism.
2. Why are agar slants better suited to maintain stock cultures over agar plates? a) they are easier to store. b) they can be flamed. c) there is more surface area for culturing. d) two or more of the answers are correct. e) they can be capped. f) none of these are good to use agar slants over agar plates.
3. Mannintol Salt Agar is considered a differential and a selective medium. Which reagents are added to the media to give it these properties? a) it contains mannitol and NaCl at 7.5%. b) it contains tryptophan and blood agar. c) it contains glucose and citrate at 7.5%. d) it contains mannitol and glucose at 7.5%. e)it contains mannitol and KCl at 7.5%
4. what is the purpose/function of the crystal violet in the MacConkey agar medium? a) it selects for gram positive microorganisms. b) it selects for gram negative mircoorganisms. c) it selects for Staphylococci. d) it differentiates between lactose fermenters and non-fermenters
5. what is the pH indicator used in the Mannitol Salt Agar? a) Phenol red. b) Bromothymol blue c) Neutral red d) Methylene blue
6. Which media would be best for fastidious organisms? a) Blood agar b) MR-VP broth c) Eosin-Methylene Blue agar d) MacConkey agar
7. Alpha hemolysis is: a) complete lysis of the red blood cells in the media b) incomplete lysis of the red blood cells in the media c) a clear halo of lysis around the colony d) no lysis of the red blood cells in the media.
8. which of the following physical factors influence the growth and survival of bacterial cells? a) pH, nutritional needs and temperature b) None of these are correct c) Temperature, nutritional needs and gas requirements d) pH, temperature and gas requirements e) pH and gas requirements
9. A selective media: a) can be used to reveal diverse growth temperature requirements of bacteria b) can distinguish among morphologically and biochemically related groups c) are only useful for fastidious organisms d) is used to select or isolate specific groups of bacteria
Explanation / Answer
1.
Pure culture is a culture that contains only one type of organisms. Option d is correct. The organisms of different morphologies and diversities are observed in mixed cultures.
2.
agar slants over plates are preferred because they can be flamed and as well capped. Hence, option d is correct.
3.
Mannitol salt agar is a selective medium to isolate Staphylocci. Mannitol salt agar contains mannitol and NaCl at 7.5%. Hence, option a is correct.
4.
The purpose of incorporating crystal violet and bile in MacConkey agar is to eliminate gram positive and fastidious gram negative bacteria and select only gram positive bacteria. Option b is correct.
5.
In mannitol salt agar the indicator used is phenol red. The bacteria metabolizing mannitol produce fermenting acidic product that causes color change red to yellow. Option a is correct.
Fastidious organisms can be detected in selective and differential media like MacConkey agar. Blood agar is used for detection of hemolytic bacteria, eosin - methylene blue agar is differential medium to detect lactose fermenters from that of non-lactose fermenters. Option d is correct.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.