Question

Lab Questions at End (picture 3)

This week in lab you will learn an important technique that microbiologists use to isolate one bacterial species from the population of other microbes it was living with in the natural environment. In most environments there are mixed populations of bacteria. For instance, 600 different types of bacteria have been isolated and identified in the mouths of humans. In soil or water there are also many types of bacteria present. In order to perform tests on a microbe of interest, it must first be isolated. Then, procedures which will lead to an identification of the microbe can be performed. This would include staining, biochemical tests, or genetic tests. Other reasons microbes need to be isolated are for research purposes, or genetic engineering. The most commonly used technique to isolate one bacterium from another is the streak plate technique. The goal of a streak plate is to start with a large density of bacteria, and thin them out so that you end up with single bacterial cells. As these single cells divide, it forms isolated colonies which you can describe and may help identify what type of bacteria you are working with. 0

QUESTIONS

Answer 1

1. Pure culture is the type culture used in this streak plate.

2. Bacteria in pure culture shows different response compared to mixed culture

    in mixed culture one species of bacteria may facilitate or weaken the response

    of other bacteria so microbiologist can use pure culture to specifically study about a

    microorganism.

3.* Pure culture can obtained in streak plate method by streaking the mixed culture across the

   surface of a agar medium with the help of a loop and during streaking the inoculum appropriately

   result in seperation of microorganisms from each other.

* After streaking out to a second area of plate using the same loop incubation should be done for

    allow the growth of bacterial colonies.

* In above case can obtain a pure culture due to use of streak plate method for isolating single colony

    of bacteria and it can observe with the help of a microscope.

4. After doing streak plate of a specimen incubate the plate for 24 to 48 hours at a temperature

    of 37 degree celcious to obtain isolated colonies.

5.Three reasons to use sterile technique in microbiology laboratory

               * Use of sterile techniques help to avoid spread of unwanted contaminated

                   microorganisms in the laboratory.

               * It prevent transfer of infections to microbiologist who work in the loboratory.

               * It directly influence accuracy of lab results about different type of infections.