Question

PART A. Your lab instructor gives you a very cloudy test tube (5 ml broth) of Serratia and tells you that you can earn 50 points extra credit if you can determine the amount of cells in the tube.

1. what is the procedure you are going to use?

2. what is the first step in the procedure

3. since the broth is very cloudy, what dilution is appropriate and why?

4. draw your set up from the previous question

5. after your set up and incubation you count 34 colonies, what is your next step?

6. what is your answer for your instructor and did you earn the extra credit?

PART B. You are not feeling well and end up in the hospital with Salmonella poisoning from contaminated tomatoes. Once you are better, you take the tomatoes to the lab to determine the number of Salmonella on the tomatoes.

7. draw how to make a 10^-4 plated dilution

8. calculate the OCC if the plate contained 188 colonies

Answer 1

1, streak plate procedure: this technique used to separate microorganism in the small sample volume that will be speard over the surface of the agar plate that makes the formation of discrete colonies distribution across the agar surface when there is a correct concentration of cells. it isolates the pure culture of colonies forms mixed populations by simple separation.
2, as a first step sterile the inoculating loop in the bursen burner by keeping the loop into the flame until it is hot and red. and make it cool.
3, Use serial dilution in sterile liquids when the number of cells is more in the colonies.
4, streak plate technique isolation method: