Portage Microbiology BIOD171 Exam 4 Questions And Answers With Explanations Of Answers.

True or False: Differential media is best suited for distinguishing between two similar species of bacteria - correct answer True Growth media does not contain restrictive factors, while selective media is best used to encourage the growth of one microbe while simultaneously discouraging the growth of the other. Since two similar species of microbes are being studied they must be differentiated under similar but just slightly different conditions (differential media). A researcher is asked to determine which of two vials contains E coli and which contains salmonella. Knowing both are Gram-negative while only one of them is capable of fermenting lactose, which type of media would be best suited? - correct answer Differential media What are the requirements of a fastidious microbe? - correct answer A fastidious microbe is an organism with complex growth requirements such that if absent it will not grow. Enriched medias thus contain these specific and essential nutrients required for the growth of a particular subset of microorganisms. True or False: LB agar is classified as a selective, non-differential media. - correct answer False. The polysaccharide-based hardening agent added to LB media to produce LB agar is derived from what? - correct answer Seaweed (algae) extract. Blood agar is which type of medium? Select all that apply. Selective Enriched Selective and Differential Differential - correct answer Enriched Differential Match the following hemolytic class with its description of activity. 1. Alpha hemolysis A. No change. 2. Beta hemolysis B. Greenish-brown color 3. Gamma hemolysis C. Distinct zone of clearing - correct answer 1. Alpha hemolysis -- B. Greenish-brown color 2. Beta hemolysis --- C. Distinct zone of clearing 3. Gamma hemolysis -- A. No change. Columbia CNA agar is most closely related to which media: - correct answer Blood agar CNA agar is similar to BAP as it is also enriched with blood and allows for differentiation based on hemolytic patterns. True or False: Chocolate agar gets its brown color from cocoa to produce an enriched media. - correct answer False Chocolate (cocoa) is never added to the media. The name is derived simply based on the color that actually comes from the presence of 'cooked' (lysed) red blood cells in the media. An unknown microbe is streaked onto a MacConkey agar plate. After an overnight incubation at 37°C, growth is observed. Would a Gram stain be necessary? Why or why not? - correct answer No. A Gram stain would not be necessary, as only Gram-Negative microbes will grow on MacConkey agar. No, because MacConkey agar only grows gram-negative microbes so therefore if there is a growth it is gram-negative. (my answer, full points) In an attempt to detect the presence of the pathogenic strain of E. coli O157:H7, a researcher spread a culture onto a MacConkey agar with failed results. What type of agar should they (correctly) try next? Based upon what you know about the formulation of differential plates, explain why you chose this specific agar. - correct answer The microbe should be plated on SMAC (Sorbitol-MacConkey agar) as it is specifically formulated to detect O157:H7. Pathogenic E. coli (O157:H7) cannot ferment sorbitol while non-pathogenic E. coli can ferment both soribitol and lactose. Therefore, colonies that ferment (acidic conditions; non-pathogenic) can be differentiated from non-fermenters (neutral to basic conditions; pathogenic). They shou