1. Why is aseptic technique important when culturing microbes? 2. Define the ter

Question

1. Why is aseptic technique important when culturing microbes? 2. Define the term inoculation with respect to microbiology . Why must an inoculating loop be flamed before placing it into a culture? must an inoculating loop be cool before touching it to a culture? s. Why should a Petri dish filled with medium not be left open for any extended period? 6. Why can a single colony on a plate be used to start a pure culture? Consider the number of individual cells in a colony of bacteria. 7. What are the two main reasons to streak for isolation? s. Why does the streaking method used to inoculate plates result in isolated colonies? 9. Why are the petri dishes usually incubated upside down (i.e., the lid is down)? o. List three ways for sterilizing culture media? 11. Using your textbook or other reputable source, find the classification of the four bacteria based on their oxygen requirement and fill in the table below Established oxygen (eg. e acrobe, ctc) subtilis Escherichia col

Explanation / Answer

1. Aseptic technique is required in culturing microbes to prevent contamination of cultures and media.

2. Inoculation is The act of introducing microorganism or suspension of microorganisms (e.g. bacteria, fungus) into a culture medium.

3. An inoculating loop must be flamed before placing it into cuture, for sterilzing it & to make it free from other organisms.

4. After flame sterilization, the inoculating loop must be cooled so that the next cells the inoculating loop touches are not killed by the hot metal.

5. A peti dish filled with medium should not to be left open for an extended period, to avoid contamination from airborne microbes

6. A single colony on a plate can make identifying the organism easier & can be use as a control into comparing other bacteria. It can reduce the chances of being contaminated by another microbial organism.

7. The two main reasons to streak for isolation are

a) It helps with isolating two different bacterial colonies.

b) It is useful when you need to separate organisms in a mixed culture or when you need to study the colony morphology of an organism.

8. When using this streaking method, between each streak we sterilize the innoculating loop in the flame. At the beginning of each new streak you dilute the one from before. This begins to dilute the bacteria by spreading it over distance and eventually the bacteria are spaced far enough apart to form isolated colonies.

9. petri dishes are incubated upside down to lessen the risk of contamination from airborne particles settling on them and to prevent the accumulation of any water condensation that may disturb the culture.

10. Three ways for sterilizing culture media are

a) Dry heat sterilization

b) auto-claving

c) Bacteriological filter.

11. Bacillus subtilis is an obligate aerobe (require oxygen)

Escherichia coli is a facultative anaerobe

Pseudomonas aeruginosa is a facultative anaerobe

Staphylococcus epidermidis is a Facultative anaerobe

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