Microbiology: Microorganisms That Co-exist With Life on Earth

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A diverse collection of microorganisms co-exist with life on Earth; most of them as inhabitants among plants or oceans, many as normal flora in humans, and some in remote locations in the most extreme habitats. Despite being ubiquitous in nature and typically harmless, bacteria get particular attention for causing disease in humans.
Correct identification of a microorganism allows for proper investigation of a particular species, and prevention or treatment of a disease if necessary. During lab, students were instructed to choose a test tube inoculated with an unknown organism and then prompted to initiate a series of appropriate lab tests to correctly identify the organism.

Unknown 3 was received in Trypticase Soy Broth. A
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Figure 1.
Test Purpose Reagents/Media Observation Results Interpretation
Gram Stain Cell wall composition, morphology Crystal violet, Gram’s iodine, Gram’s Decolorizer, Safranin Counterstain Purple circles, clustered in tetrads + Gram positive cocci
Methyl Red Detect mixed acid fermentation MR-VP broth, Methyl Red reagent No change in color - Non-fermenter
Urea hydrolysis Detects enzyme urease Urea broth Yellow color - Does not metabolize urea

Figure 2. Unknown Organism #3

Gram Stain Gram (+) Rod Gram (-) Rod Gram (+) Cocci S. aureus S. epidermidis E. faecalis M. luteus M. roseus

Pigmentation (+) (-) S. aureus S. epididermidis M. luteus E. faecalis M. roseus

Methyl Red (+) (-) S. aureus M. luteus M. roseus

Urea Hydrolysis (+) (-) M. luteus M. roseus Micrococcus roseus DISCUSSION
Unknown 3 was identified as Micrococcus roseus (M. roseus), a gram positive cocci found in soil,

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