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Report on Identification of Unknown Bacteria
Name:
Date:
Section Day & Time:
TA Names:
Unknown #s:
Statement of Purpose:
Identification of Unknowns:
Gram-Positive
Organism
Gram-Negative
Organism:
Written Summary of Procedure:
S.epidermidis
E.hoshinae
This experiment was conducted to isolate pure culture from a mixture of two
unknown bacteria. Once pure culture were obtained, metabolic tests were utilized
to determine the two unknown bacteria organisms.
To identify two unknown bacterial organisms, a pure culture of each of the unknown
organisms were microscopically examined and then a biochemical tests were
performed in order to determine them. On day 1, a saline suspension with two
unknown bacteria were given and three phase streak were performed to separate the
two bacterial organisms. After using a good aseptic technique, the TSA plate was
incubate at 37 C for 24-48 hours. On day 2, a well isolated colony of each type of
organism were obtained and a gram staining were performed. Gram status has been
obtained in order to generate a pure cultures of each of the organisms. A three phase
streak plate of each organism were incubated at 37C. On day 3, the two pure cultures
were obtained and examined by the TA and the appropriate test should be identified
from the approved flow chart in order to identify the two organisms. For gram positive
bacteria, catalase and mannitol tests were utilized to identify the unknown organism.
For gram negative bacteria, KIA ph of tube was used to determine the other metabolic
tests in order to identify the unknown organism. H2S production and citrate test were
performed to identify the organism.
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Graphical Representation of Procedure (Dichotomous Flowchart):
Be sure to review the lab PowerPoints for insight on how to construct a truly dichotomous flowchart. Should
take up almost a full page.
Gram stain
b b
Gram -1 Gram –
KIA
v v Phtvbe
Coccus Bacillus ~
E. aerogenes
catalase E. hoshinae
test P. mirabilis
Matvei
r
v
negative positive
I
/ KIA
5. areas Hzs production
5.epidemidis
r r
/ mannitol test positive Negative
v v
E. hoshinae positive Negative
p.mirabilis
v
5. epidermidis
citrate test
u
v
Negative
Positive
E. hoshinae
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Data Collected:
Table 1 – Macroscopic and Microscopic Characteristics of Each Unknown
Gram
Reaction
Cellular
Morphology
Cellular
Arrangement
Colony Morphology
(If known or published online)
G+
G
Table 2 – Metabolic Test Results for Gram-Positive Unknown Organism
Test Expected Observations Expected Result
NOTE: If you used only one
test to ID your Gram-positive
unknown, delete this row from
your table.
Coccus Cluster Convex shaped
Bacillus Chains Rod shaped,
single
Catalase
Mannitol
Expected to have no
change for negative
test result, and observe
bubbles if the test
result is positive.
Positive results which
indicates the production of
bubbles, the production of
enzyme catalase.
The expected
observation of this test
is a change in the color
if the test is positive
and no color change if
it is negative.
Negative result because there is
no indication of color change
which translates to no acid
production.
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Table 3 – Metabolic Test Results for Gram-Negative Unknown Organism
Test Expected Observations Expected Result
NOTE: If you used only one
test to ID your Gram-negative
unknown, delete this row from
your table.
KIA H2S
production
Citrate
Expected to observe
color change and
black precipitation if it
is positive result.
A black precipitation formed
which means the test result is
positive.
Color change if the
result is positive and no
color change observe if
the result is negative.
The test result was
negative and that
indicates no color change
which means there is no
ph change of the medium.
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Discussion:
Include – brief summary of methods (2-4 sentences), interpretation/discussion of each of the results in the
tables above, discussion of each expected result in table on page 217 in lab manual, identification and
justification of whether microbe would survive better in an anaerobic or aerobic environment.
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Further Research:
Split into 1-2 paragraphs for each organism, be sure to include in-text citations where appropriate
Conclusion:
Your conclusion should not simply repeat your discussion, you should begin by restating the purpose, briefly
(1 sentence) summarizing how you accomplished this/your methods, and identify your two unknowns. You
can then include 1-2 sentences about what was learned about each unknown from further research.
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References:
Be sure to include all references cited throughout the document.