This past week has been my first week as a STEM
intern. I started Monday at noon and my journey began with some very long and
informative safety videos. Although they were boring they are important and
essential. After the videos I had to find out what an "isolation
streak" and a "lawn streak" were. I then had to actually do an
isolation and lawn streak with mystery bacteria #7 given to me by Josh. My
first attempts on the streaks were not very good due to me literally stabbing
the TSA. I tried it again and my second attempt were much better after Josh
demonstrated how to do it properly. Drawing the “T” on the bottom of the dish
really helped as well. I put my first and second attempts of streaks in the
incubator for 24 hours to see my results.
These
are my first and second attempts for the isolation streak. “T” definitely help
My
second attempt (right) seemed to have grown some type of mold quite obviously.
On Tuesday I had to find out what a “gram stain” was
and figure out how to do a gram stain on my unknown bacteria. So I found out
that a gram stain is a way to figure out what type of cell wall (gram negative
or gram positive) and shape the bacteria has to differentiate it from other
bacteria to narrow down what type of bacteria it is. So the process was to grab
a slide and put a drop of water on it. I then grabbed some bacteria and smeared
it on the slide on the water. I got an oil lamp and heated the slide by passing
it on top of the fire until the water dried up and left only the bacteria.
After that I put a drop of crystal violet on the bacteria and left it for 30
seconds and rinsed it off with water. Next I covered the bacteria with Gram’s
Iodine for one minute and rinsed. The decolorizer was next for 15-30 seconds
and rinse. Last was the Safranin for about a minute and rinse off. Blot dry
with the bibulous paper and finally put the slide under the microscope and look
for the cell morphology. Mine turned out to be a gram positive coccus.
I had figured out that my cell morphology was
coccus, which is circular shaped cells. I also found out through the gram stain
that my unknown bacteria was gram positive since it was purple. From that
information I followed the positive gram cocci chart and the next step was to
do a catalase test. The catalase test purpose is to identify if the bacteria
generates the enzyme catalase. I needed some hydrogen peroxide for this test. I
grabbed a slide and made two circles one for the test and the other for
control. I put a drop of distilled water on both circles and smeared some
inoculum (bacteria). I put one or two drops of hydrogen peroxide on the Test
circle and none on the control. The reason for this is to see if the hydrogen
peroxide will make the bacteria bubble or not. If the bacteria does bubble then
it means that it is catalase positive. The C circle is to compare with T
circle. My bacteria did bubble so it is
catalase positive.
Now that the bacteria have been identified to have
positive catalase enzymes, the next step is to do glucose fermentation. I
simply transferred a few drops from by unknown bacteria tube to the glucose
tube and put it in the incubator for 24 hours. The next day I grabbed my
glucose tube from the incubator and saw that it turned bright yellow. This
means that my bacteria is a positive acid and it did not produce any gas.
Finally I did an MSA test today to see if my bacteria can withstand a high salt
concentration environment. I did an isolated streak on an MSA medium today and
placed it in the incubator for 24 hours. Next week I will check my results.
Overall I have really enjoyed this mini project so far because it’s really
“hands on” learning and it’s interesting to see how many test are done on a
bacteria. The other interns seem really cool as well and seem to be enjoying their
projects too.
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