Question

Describe the steps of aseptic technique when transferring culture to a plate.

Describe the steps of streaking for isolation. What is the goal of streaking a plate this way?

Please post with typed responses - no handwritten or picture responses.

Answer 1

Hi Answer:

Q.1. Describe the steps of aseptic technique when transferring culture to a plate.

Answer: The contamination-free transfer of culture grown in a tube or flask and its transfers to the agar plate is a multistep process. The various steps of this process are as follows:

1.     Grow preserved culture in a sterile growth media for example in LB broth.

2.    Another side prepared Agar medium e.g. LB agar and autoclave it and pore in the plates to prepare sterilized gar plates. These poring plating should be carried out in sterile conditions and place such as Laminar air flow. It also makes sure that the plates which are used to prepare the agar plates must be sterilized either by autoclaving or disposable sterile plates purchased from the company.

3.    After agar media sterilization pore this media into the sterile plates and allow it to solidify for 10-15 minutes in laminar air flow under UV light.

4.     Now take a streaking loop and dip into disinfectant and then heat sterilize it by exposing the loop to the flame and let it cool.

5.    After cooling the loop dip this loop into the broth culture and carefully streak the culture on the solidified agar plate. Make sure there will be no repetition of the streaking on plates so that there will be uniform colonies of the organism will grow on the plates.

6.    Close the lid of the plate gently and seal it with paraffin film and put in the incubator for the growth.

Q. 2. Describe the steps of streaking for isolation. What is the goal of streaking a plate this way?

Answer: The streaking is the process of isolating the pure single colonies of organisms from a culture. It is the most important step of the isolation procedure. The major goal of streaking is to isolate various organism present in a mixed culture.

The various steps of streaking as follows:

1.    Prepare sterile agar plates.

2.    Sterile the streaking loop under the flame and let it cool.

3.    Dip the loop into the culture and start streaking on the plate. It is advised that always streak the culture by making a square on plate means start from a point and make straight line to one side of plate. Then warm the loop and let it cool after cooling again make line to another side (these lines never intersect each other) repeat the whole process 2 time more for each plate. [ the heating of loop in the middle of the streaking is to reduce the number of colonies in successive streaking lines].

The image of a well-streaked plate is given below it show the direction how to streak plate properly. in below figure it is shown that start streaking from point 1 after that heat th eloop and cool it then move to point 2 again heat the loop and aftr cooling move towrds the 3 point. In same way point 4 and 5 is drwan. You can clearly see in figure the straking lines are not intreseting each other whethey are hrizontally drawn and only every point intersect other line at corners. This is necessary to reduce the number and over lapping of colonies.