Time is flying by at the Cheung Lab!
I have finished my third week in the lab and
I feel like I just got here.
I am
starting to see the results of my work which is very exciting! This week I
continued to grow the 61 potentially cold-sensitive
MRSA strains that had difficulty growing in cold temperatures on agar plates the previous week in liquid media at three different temperatures
to better observe their growth. I tested around 5 different strains per day. Every
hour for 6-7 hours, I checked the optical density (OD) of each culture (I also made 10 fold dilutions when necessary since the spectrophotometer does not give accurate readings once the optical density reaches 0.7). Next, I made a growth curve using the
resulting ODs.
I also
began using the ODs to find the growth rates of each strain at
the three temperatures to determine if and how much temperature has affected the growth rate of the mutants
and to back up the information provided by the growth curves.
At first, I had a few challenges trying to
calculate the growth rate because depending on which data points I used, the
growth rate did not accurately reflect the growth curves that I’ve been
making.
However, after some trial and
error I determined which ODs were best to use in order to find a more accurate
growth rate.
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These are the mutant S. aureus strains grown at three different temperatures. As you can see, the culture on the left (which was grown at the optimal temperature for S. aureus, 37 C) is more turbid, showing faster cell growth, and the culture on the right (which was grown in cold conditions) is the least turbid, showing the slowest cell growth. |
I have also started researching some of the known genes that
were knocked out of the potentially cold-sensitive MRSA strains to learn more about the proteins that they encode and their relation to bacterial cold shock response. However, some of the genes encode "conserved hypothetical proteins", which basically means that the proteins' functions are unknown. This was also exciting to find because these unknown proteins could possibly be cold shock proteins.
I am almost finished observing the growth of the potentially cold-sensitive MRSA strains (I will probably finish next week) and I am excited to move on to the next step of my experiment, transduction!
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