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Lab 3-5 Homework copy FINAL VERSION

Lab 3-5 Vanessa Andrade Wendy Nieto Gissel Rodriguez
Feb 5, 2020
1. Where you able to achieve a good quadrant streak? If not, explain what may have gone
wrong with your aseptic technique or streaking technique based on the results.
a) (wendy) I believe my streak was not the best because you can hardly see any growth.
Reason might be because it has not had enough time in the incubator to fully grow any
bacteria you can mostly see the bacteria along the edges of quadrant 1 and fully on
quadrant 2. I don’t believe my aseptic techniques had any wrong doing as to why there
isn’t any full bacteria on my plate.
b) (gissel) I managed to achieve a decent quadrant streak Bacteria was able to grow on the
rim of the agar plate, However cannot see the streaks. I think if I used a more gentle
touch when streaking, I would have had a more uniformed quadrant streak as well as to
wait for the loop to really cool down in order for the agar to not be lifted.
c) (Vannessa) My quadrant streak was not the best. I would need to use a better hand next
time in order to prevent damage to the agar itself. I hope to achieve better colonies with
a lighter hand and better, even streaks.
2. Describe the cell morphologies seen in each photo above. Draw arrows to indicate specific
a) (wendy) In the picture above we can see several morphologies of Bacillus.
b) (gissel) Some cell morphology that were seen in my sample were Streptobacilli,
pallsades and Bacillus.
c) (Vannessa) In the picture above we see all over the slide Bacilli morphologies.
3. Based on your ocular micrometer calibration, what is the diameter in microns (micrometers)
of a single cell from each photo above? Show your work!
(wendy): I measured the one in the circle that is singled out.
a) 3 (O.U) X .001mm
1 o.u
= 3 (o.u) x .001mm
=.003mmx1000= 3μm
objective 100x oil total magnification 100x calibration 1o.u=.001mm
(gissel) measured picture above
6(o.u) x .001mm x 1000 = 6μm
4(o.u) x .001mm x 1000= 4 μm
1 (o.u)
objective=100x +oil
total mag 1000x
calibration =1.ou= .001mm
4. Explain what would happen if you used nigrosine for this simple stain instead of crystal
violet? What would your stain look like? Use the Table of stains shown later in this Powerpoint
to thoroughly answer this question.
 If nigrosine were to be used in this experiment instead of crystal violet. The background
of the sample would have been stained instead of the cells. Also crystal violet has a
positive charged auxochrome which will then attached to the slightly negative charged
cell in our sample allowing is to view the morphology the shape and arrangement of the
bacterial cells, unlike nigrosine where it has a negative charged auxochrome which will
then repel the cells morphology