Question

Prelab 9: Selective Media Read pages 227-230 and 241-256 in your lab manual, watch the video, and answer the following questions in your own words before coming to lab. Chapter 6 in your textbook may also be helpful. You may also want to review the video on inoculation techniques. (I will hand out a written procedure for the KOH test in lab.) NOTE: for all these procedures over the next few weeks, you will be testing only your assigned organism on the given media. 1. Why are plates inverted (agar side up) while they're incubated? 2. When picking up bacteria growing on a solid medium to transfer to a new culture, do you need to scrape up a huge visible amount? Explain. 3. Instead of incubating a separate control plate, you will leave a space on your plate uninoculated as a control. One reason for this control is to show what color the medium is without microbial growth; why is this necessary? What is a second thing that this control tells you about the experiment?

Answer 1

1. The plate is incubated inverting for-

Avoid any contamination from air settled particles.

To avoid any water droplets down upon the agar media.

2. No, we don't need to take a huge visible amount. Just touch and scrap a fraction by your inoculation loop to a colony which you wants to reinoculate and transfer them to a new plate.

3. One uninoculated plate is incubated separately because it acts as a control as well as help to compare the other tested plates with it.

Italso helps to see that where is any contamination or not, that is proper sterilization.

It's also shows that any unwanted changes occurs in the plate is due to media or by microbes.

Thanks...............!!!!!