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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.

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

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? 

Name an organism (genus and species) we worked with in the Lab Exercise that is a strong lactose fermenter. 

What are the two selective ingredients used in EMB agar?

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

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?

View the Acid-fast stain below: What conclusion can be drawn about the majority of the cells present in this sample?  

View the Acid-fast stain below: What conclusion can be drawn about the majority of the cells present in this sample?