Microbiology Lab Exam # 1 Questions and Answers

Microbiology Lab Exam # 1 Questions and Answers Considering the cultures used to inoculate each medium in this exercise, how many different microbial types should you expect to see in/on each medium? (1.4) -Answer- You should only have 1 if using good sterile technique. A successful aseptic transfer will have only micrococcus lutes growth- this would be a pure culture You were asked to describe differences in appearance of growth in each culture, if present. In which medium was this the most difficult to determine? What made it difficult? (1.4) -Answer-More difficult to see in broth because you can only see if growth occurred on the top or bottom etc. Better in slant because you can observe different growth patterns. Which medium was most difficult for you to transfer from? Which medium was most difficult for you to inoculate? Why? (1.4) -Answer-Most people don't like working with slants (solid) If you got growth on sterile NA and NB slant rubes, why? (1.4) -Answer-Possible contamination include not heating the loop to orange-hot, not holding the open tubes on an angle, and/or placing the cap on the table surface during the process. Did you notice a difference in density (turbidity) of growth in NB tubes inoculated from NB and NA slants? Possible reasons?( 1.4) -Answer-Generally, more cells are transferred from growth on a solid medium than from a broth culture. Therefore, broth cultures made from growth on a solid medium will show greater turbidity than those inoculated from a broth culture. Did you notice a difference in density of growth on NA slants inoculated from NA slants and NB? (1.4) -Answer-Generally there will be denser growth on the slant inoculated from the NA slant, because more cells are transferred from solid medium than broth. Pure culture (1.4) -Answer-When a culture ( a medium that contains living microbes) contains a single species. Broths (1.4) -Answer-A medium used to grow microbes when fresh cultures or large numbers of cells are required. Used for ID. Agar Slant (1.4) -Answer-A type of medium used to grow stock cultures that can be refrigerated after incubation and maintained for several weeks. Plated Media (1.4) -Answer-A type of medium used for obtaining isolation of species, differential testing, and quantifying bacterial densities. Inoculating loops (1.4) -Answer-An instrument used to inoculate a medium. Inoculation (1.4) -Answer-To introduce (cells or organisms) into a culture medium. Using a pencil, draw a quadrant streak (1.5) -Answer-Should look like this. You should also rotate a little less than 90 Degrees each streak, and heat the loop so you can get good results. Also, let the loop cool!! Mixed Culture (1.5) -Answer-A microbial culture consisting of two or more species. What is generally the first step in identifying a microbial organism? (1.5) -Answer- Obtaining isolations of Individual colonies. The technique we used in class was the isolation technique- the streak plate. Cells that have been sufficiently isolated will grow into colonies, consisting only of the original cell type. Colonies (1.5) -Answer-Individual microbial cell type. They can also form from a pair, chain, or cluster of cells. Colony Forming Unit (CFU) (1.5) -Answer-A more correct description of the colony origin Zigzag Inoculation (1.5) -Answer-A type of inoculation pattern used to when the sample does not have a high enough cell density. Quadrant streak technique: (1.5) - how much space should you try to use? - describe what each of the quadrants should look like - describe order -Answer-- maximize the space used - Q1: confluent growth (colonies overlapping), max growth - Q2: less growth, some separation - Q3: even less growth - Q4: isolated colonies - flame, only go to culture once at the beginning, Q1, flame, Q2, flame, Q3, flame, Q4, flame Quadrant plate questions: (1.5) - What if no overlap? - too much overlap?