Discussion The main motive to perform this study was to determine the presence of unknown microorganisms present in the provided sample.

Create a 2 pages page paper that discusses biol 260-microbiology (bacterial unknown ). Discussion The main motive to perform this study was to determine the presence of unknown microorganisms present in the provided sample. This study encompasses classification of bacteria based on their chemical reactions temperature, pH levels and osmoregulation. It is very imperative to classify the bacteria and to identify these microorganisms as they have enough potential to cause various diseases. This is essential to carry out the correct diagnosis and treatment of the individual. Identification of the bacteria provides line of treatment.

As the preliminary examination about the unknown sample, Gram Staining was performed to categorize bacteria into Gram positive or Gram negative. On the basis of morphology after performing Gram staining one was identified as Gram positive Cocci while other was identified as Gram negative Bacilli.

A. Gram positive Cocci-

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Further, colony characteristics, biochemical tests as well as specific tests the micro-organisms were carried out to reach to the correct identification of the micro-organism. The Catalase test was performed which was positive, eliminating the chances of unknown sample to be Streptococcus (which is catalase negative). Further, Mannitol fermentation was positive for this unknown sample which eliminates the chances of S. aureus (Mannitol negative) from the sample. Further, presence of pigment was observed to eliminate the chances of S. epidermidis and S. saprophyticus (both these organisms do not have pigment). Since the colony color was found to be yellow the identification tapers to the presence of Micrococcus sp. In order to further segregate the Micrococcus sp. presence or absence of glucose fermentation was observed. The result was negative confirming the absence of Micrococcus varians (which displays glucose fermentation) and presence of Micrococcus luteus (does not display glucose fermentation).

B. Gram negative very short rods-

The second unknown bacteria was aerobic as it was catalase as well as oxidase positive. Since it is Gram negative aerobic bacilli the identification tapers to the possibility of either Helicobacter salinarum, Alcaligenes faecalis, Pseudomonas aeruginosa. Since citrate utilization was positive in the biochemical test it could be Pseudomonas aeruginosa or Alcaligenes faecalis. To eliminate one of the species to taper the identification further, growth was observed which was moderate and hence probability of Pseudomonas was eliminated (as Pseudomonas display abundant growth).


Manipulative skills and cognitive microbiological knowledge are essential for the identification of microorganism beyond their genus classification, i.e. to their species identification. The use of previously performed experiments and procedures laid the foundation of dichotomous keys, Bergey’s Manual of Systematic Bacteriology. This key aids in the classification of microorganisms and to identify the causal organisms. Further, biochemical tests successfully accomplish the experimental purpose. Species identification can be accomplished by using various established laboratory procedures. Spurious results may be obtained in some cases that departs from the expected norms for a particular species, may be attributed to strain differences within the given species. The unknown samples are required to be handled with care and precision.


William, H. “Bergeys Manual of Determinative Bacteriology.” Baltimore: Lippincott Williams and Wilkins, 2000. Print.

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