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Serial ten-fold dilutions are made from a broth culture of Bacillus subtilis in order to determine the number of bacteria in the culture.  Following the dilution series, 0.1 ml of a 1:10,000 (1 x 10-4) dilution is plated, the plate is incubated, and 110 colonies are counted.  Calculate the number of bacteria in the original Bacillus subtilis culture. Don’t forget units! Cannot earn full credit without proper units. Make sure your answer reflects proper scientific notation! Use the ^ to denote an exponent, i.e. 1 x 10-4 would be written as 1 x 10^-4.

These cells were stained using one of the differential staining protocols we covered in lab.  What was cellular structure was decolorized during the decolorizer step of this staining technique? 

Four different species of bacteria were streaked on this EMB plate and incubated. What conclusion(s) can be draw about species A?   

These cells underwent one of the differential staining protocols we covered in lab. Which bacterial genus do these cells most likely belong to?   

What are the two selective ingredients used in EMB agar?

Based on the growth patterns on the agar plates: Identify the temperature class of species A: [a] Give an example of an organism that belongs in the same temperature class as species A: [b].  (write out full genus and species)  

How many times do you place your sterile loop into the stock culture of bacteria when performing a streak plate?

You need to transfer 110 microliters of water into a microfuge tube. You have three micropipettes at your disposal: a P20, a P200, and a P1000. Answer the following questions: A. Which pipet should you use? [a] B. In order to transfer the proper volume, what numbers should be displayed on the pipet? [b] C. When drawing up liquid, do you press down to the first or second stop? [c] D. When expelling liquid, do you press down to the first or second stop? [d]

Identify the following bacterial morphologies: A. [a] B. [b] C. [c]

For each characteristic listed below, indicate whether it is a property of Gram-positive bacteria, Gram-negative bacteria, or both. Has a thin layer of peptidoglycan [a] Has an outer membrane [b] Contains teichoic acid [c] Contains lipopolysaccharide [d] Has a periplasmic space [e] Has a cytoplasmic membrane [f] Has a thick layer of peptidoglycan [g] Contains lipoteichoic acid [h]