BIOD 171: MODULE 4 Complete Assignment With Questions And Answers Guaranteed Success Save

T/F: Growth media is best suited for distinguishing between two similar species of bacteria - ANSWERSFalse growth media is designed to simply support (and not restrict) microbial growth 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? - ANSWERSDifferential media What are the requirements of a fastidious microbe? - ANSWERSA fastidious microbe is an organism with complex growth requirements and will not grow without then. Enriched medias thus contain these specific and essential nutrients required for the growth of a particular subset of microorganisms. T/F: LB agar is classified as a non-selective, non-differential media - ANSWERSTrue The polysaccharide-based hardening agent added to LB media to produce LB agar is derived from what? - ANSWERSSeaweed extract Blood agar is which type of medium? Select all that apply: - Selective and Differential - Enriched - Differential - Selective - ANSWERS- Enriched - Differential Match the following hemolytic class with its description of activity: 1. Alpha hemolysis 2. Beta hemolysis 3. Gamma hemolysis A. No change B. Greenish-brown color C. Distinct zone of clearing - ANSWERS1. Alpha hemolysis- Greenish-brown color (B) 2. Beta hemolysis- Distinct zone of clearing (C) 3. Gamma hemolysis- No change (A) Match the following hemolytic class with its description of activity: 1. Alpha hemolysis 2. Beta hemolysis 3. Gamma hemolysis A. No hemolytic activity B. Incomplete hemolytic activity C. Complete hemolytic activity - ANSWERS1. Alpha hemolysis- Incomplete hemolytic activity (B) 2. Beta hemolysis- Complete hemolytic activity (C) 3. Gamma hemolysis- No hemolytic activity (A) Columbia CNA agar is most closely related to which media: - ANSWERSBlood agar CNA agar is similar to BAP as its also enriched with blood and allows for differentiation based on hemolytic patterns T/F: Chocolate agar gets its brown color from cocoa to produce an enriched media - ANSWERSFalse chocolate 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 A researcher is studying a strain of E. coli currently growing on a MacConkey plate. However, the researcher can't remember if E. coli is Gram-positive or Gram-negative. Would a Gram stain be necessary to confirm? Why or why not? - ANSWERSNo, because gram negative microbes only grow on macConkey agar 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? Why? - ANSWERSThe SMAC should be tried next because it can be differentiated by lactose fermentation and sorbitol fermentation, both of which can be fermented by the non-pathogenic strain What is the Gram status (positive or negative) of microbes growing on Eosin Methylene Blue (EMB) agar plates? - ANSWERSGram-negative because gram positive bacteria growth is restricted by EMB plates Mannitol salt agar will turn what in color in the presence of the pathogenic strain Staphylococcus aureus? - ANSWERSYellow What is the process of spreading a bacterial culture onto a petri dish called? - ANSWERSPlating Describe the primary advantage of using a petri dish over growing a liquid culture - ANSWERSThe primary advantage is that cells are held into place. When grown in a nutrient broth, bacterial cells can multiply but are free to move around in the solution. When grown on agar within a petri dish they are fixed in a way to form colonies. T/F: The visualization of colonies on a petri dish represents bacterial cells that have often multiplied a million times over - ANSWERSTrue To form a bacterial colony the initial cell must have multiplied many "times over, ofen greater than a million, in order for the naked eye to resolve it. T/F: The purpose of a quadrant streak is to expand a bacterial population - ANSWERSFalse The purpose of the quadrant streak is to generate individual colonies such that a single bacterial sample can be isolated To be considered a pure culture, the sample (1) can be traced back to a single cell and (2)__________ - ANSWERSfree of external contaminants When performing a quadrant streak, the ample is spread across the plate in such a way to form what? - ANSWERSA dilution gradient. In what phase of a dilution streak would you expect to find the lowest concentration of bacteria, P2 or P4? - ANSWERSPhase 4 P4 (Phase 4) would contain the lowest concentration of bacteria. The phases rank (from highest to lowest), P1 P2 P3 P4. T/F: When performing a dilution streak a new (or sterilized) loop must be used for each phase - ANSWERSTrue Failure to do so would prevent the establishment of a dilution gradient, as the same bacterial concentration would be spread across both phase regions. In order to encourage growth of slow growing microbe what might a researcher do during a phase dilution streak? - ANSWERS- opt to perform only a 3-phase dilution streak or - pass the loop through the previous phase multiple times T/F: Pathogenic strains of bacteria tend to grow slower than normal non-pathogenic bacterial strains - ANSWERSFalse Pathogenic strains of bacteria tend to grow faster than non-pathogenic strains at 37 degrees celsius which is why researchers may set incubators at 25 degrees celsius to restrict growth When given an unknown bacterial sample the first step is to expand the current bacterial population. Which form of media best suites this need? Why? A. MSA agar B. LB media containing ampicillin and neomycin C. MacConkey agar D. Blood agar - ANSWERSD. Blood agar. All the other options are forms of selective media and will inhibit the growth of the unknown sample. Although Blood agar is a differential media, its most importantly non-selective True or False: Differential media is best suited for distinguishing between two similar species of bacteria. - ANSWERSTrue Growth media does not contain restricive 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 if a sample contains Neisseria meningitides. Knowing Neisseria meningitides is slow growing and other foreign microbes may also be present in the culture, which type of media would be best suited? - ANSWERSSelectiva Media Selective media. If additional foreign microbes may be present in your sample and you know Neisseria meningitides is slow growing, you must restrict the unwanted microbes while supporting the growth of Neisseria meningitides. Thus, you are selectively encouraging one microbes growth, while selectively restricting others. T/F: LB agar is classified as a selective, non-differential media - ANSWERSFalse LB agar is the most basic type of agar and like LB, supports the growth of virtually all microbes without restriction 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? - ANSWERSNo, a gram stain would not be necessary, bc only gram-negative microbes will grow on a MacConkey agar Which type of agar media is best suited to support the growth of Staphylococcus? - ANSWERSMannitol salt agar True or False: The visualization of colonies on a petri dish represents bacterial cells that have multiplied ~2-3 times. - ANSWERSFalse When an individual colony is visible on agar, the bacterial cell has multiplied often a million times over True or False. The purpose of a quadrant streak is to produce individual colonies of a bacterial population. - ANSWERSTrue True or False. When performing a dilution streak a new (or sterilized) loop is not required for each phase as long as the bacterial culture is pure. - ANSWERSFalse a new or sterilized loop is absolutely required for each phase The number of phases (3 vs. 4) and/or the number of times a loop passes through a previous phase (once vs. multiple times) is acceptable provided what happens? - ANSWERSEither is acceptable provided that the resulting quadrant contains growth of individual colonies within it and if it doesn't, the experiment has to be redone. What is agar used for in microbiology? - ANSWERSAgar is used to create a solid, smooth surface on which microbes can grow. In Eosin Methylene Blue (EMB) agar, what color indicates the presence of E. coli? - ANSWERSMetallic Green In order to visualize individual colonies of bacteria would you culture your sample in a liquid media or on a solid (agar) media? Why? - ANSWERSSolid (agar) media because the primary advantage is that cells are held into place. When grown on agar in a petri dish, it's fixed in a way to form colonies. In a nutrient broth, bacterial cells can multiple but are able to freely move around in the solution. A dilution gradient is formed when carrying out what generalize plating strategy? - ANSWERSQuadrant streak T/F: Growth media is best suited for distinguishing between two similar species of bacteria - ANSWERSFalse growth media is designed to simply support (and not restrict) microbial growth 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? - ANSWERSDifferential media What are the requirements of a fastidious microbe? - ANSWERSA fastidious microbe is an organism with complex growth requirements and will not grow without then. Enriched medias thus contain these specific and essential nutrients required for the growth of a particular subset of microorganisms. T/F: LB agar is classified as a non-selective, non-differential media - ANSWERSTrue The polysaccharide-based hardening agent added to LB media to produce LB agar is derived from what? - ANSWERSSeaweed extract Blood agar is which type of medium? Select all that apply: - Selective and Differential - Enriched - Differential - Selective - ANSWERS- Enriched - Differential Match the following hemolytic class with its description of activity: 1. Alpha hemolysis 2. Beta hemolysis 3. Gamma hemolysis A. No change B. Greenish-brown color C. Distinct zone of clearing - ANSWERS1. Alpha hemolysis- Greenish-brown color (B) 2. Beta hemolysis- Distinct zone of clearing (C) 3. Gamma hemolysis- No change (A) Match the following hemolytic class with its description of activity: 1. Alpha hemolysis 2. Beta hemolysis 3. Gamma hemolysis A. No hemolytic activity B. Incomplete hemolytic activity C. Complete hemolytic activity - ANSWERS1. Alpha hemolysis- Incomplete hemolytic activity (B) 2. Beta hemolysis- Complete hemolytic activity (C) 3. Gamma hemolysis- No hemolytic activity (A) Columbia CNA agar is most closely related to which media: - ANSWERSBlood agar CNA agar is similar to BAP as its also enriched with blood and allows for differentiation based on hemolytic patterns T/F: Chocolate agar gets its brown color from cocoa to produce an enriched media - ANSWERSFalse chocolate 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 A researcher is studying a strain of E. coli currently growing on a MacConkey plate. However, the researcher can't remember if E. coli is Gram-positive or Gram-negative. Would a Gram stain be necessary to confirm? Why or why not? - ANSWERSNo, because gram negative microbes only grow on macConkey agar 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? Why? - ANSWERSThe SMAC should be tried next because it can be differentiated by lactose fermentation and sorbitol fermentation, both of which can be fermented by the non-pathogenic strain What is the Gram status (positive or negative) of microbes growing on Eosin Methylene Blue (EMB) agar plates? - ANSWERSGram-negative because gram positive bacteria growth is restricted by EMB plates Mannitol salt agar will turn what in color in the presence of the pathogenic strain Staphylococcus aureus? - ANSWERSYellow What is the process of spreading a bacterial culture onto a petri dish called? - ANSWERSPlating Describe the primary advantage of using a petri dish over growing a liquid culture - ANSWERSThe primary advantage is that cells are held into place. When grown in a nutrient broth, bacterial cells can multiply but are free to move around in the solution. When grown on agar within a petri dish they are fixed in a way to form colonies. T/F: The visualization of colonies on a petri dish represents bacterial cells that have often multiplied a million times over - ANSWERSTrue To form a bacterial colony the initial cell must have multiplied many "times over, ofen greater than a million, in order for the naked eye to resolve it. T/F: The purpose of a quadrant streak is to expand a bacterial population - ANSWERSFalse The purpose of the quadrant streak is to generate individual colonies such that a single bacterial sample can be isolated To be considered a pure culture, the sample (1) can be traced back to a single cell and (2)__________ - ANSWERSfree of external contaminants When performing a quadrant streak, the ample is spread across the plate in such a way to form what? - ANSWERSA dilution gradient.