Microbiological Identification and Characterization of Serratia marcescens: Insights from Gram Staining and Urease Testing

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The unidentified microorganism provided was placed in a petri dish labeled C14. Conducting experiments in the Microbiology laboratory, coupled with subsequent research on the outcomes, facilitated the identification of the organism. Once identified, further research delved into diseases associated with the organism and explored treatments to combat those diseases.

Table 1: Testing results for Serratia marcescens
Test	Purpose of test	Reagents/Media	Observations	Results
Gram Stain	The purpose of the Gram stain test was to determine the Gram stain reaction of the bacterium. Don't use plagiarized sources. Get your custom paper on “ Microbiological Identification and Characterization of Serratia marcescens: Insights from Gram Staining and Urease Testing ” Get high-quality paper NEW! smart matching with writer	Crystal violet, Gram’s Iodine, 95% ethanol, and Safranin were used in the Gram stain test.	The organism appeared bacillus-shaped, stained purple in color and could either be arranged in chains or clusters.	Gram negative
Urease Test	The purpose of the urease test is to determine if the organism is positive for the urease enzyme and therefore belongs to the Genus Proteus.	Nutrient broth deeps, pH indicator, phenol red.	The broth was yellow in color.	Negative for the urease enzyme

The objective of this laboratory experiment is to identify the unknown microorganism labeled C14.

Through a series of careful observations and experiments, we aim to determine the characteristics and properties of the bacterium. The initial observations of the organism on the petri dish indicated distinct changes in color and morphology over a one-week period.

Observations and Morphological Changes:

Upon receiving the unknown organism in plate C14, initial observations revealed a raised and light pink-colored bacterium. Subsequent observations after a week indicated that the organism remained raised, but the color had transformed into a darker brick shade.

These changes in color and morphology serve as important clues in identifying the microorganism.

Gram Stain Experiment:

To further characterize the unknown organism, a Gram stain experiment was conducted. The Gram stain is a widely used technique in microbiology to differentiate bacteria based on their cell wall structure. Gram-positive organisms possess a thicker peptidoglycan layer in their cell wall compared to Gram-negative organisms, leading to distinct staining patterns.

Procedure:

Bacterial Smear Preparation:
- A sterile inoculating loop was used to create a bacterial smear on a slide.
- The smear was heat-fixed to ensure adherence of the bacteria to the slide.
Primary Stain – Crystal Violet:
- Crystal Violet was applied to flood the bacterial smear, staining all cells purple.
Mordant – Gram’s Iodine:
- Gram’s Iodine was used to bind to the Crystal Violet and the cell wall, forming a complex.
Decolorization – 95% Ethanol:
- 95% Ethanol was applied to selectively remove dye based on certain cell wall characteristics.
- Gram-positive organisms retain the primary stain, while Gram-negative organisms become colorless.
Counterstain – Safranin:
- Safranin was used as a counterstain, binding to colorless Gram-negative organisms and turning them pink.

The Gram stain experiment revealed that the unknown organism in plate C14 appeared pink in color after the application of Safranin. This outcome confirms that the organism is a Gram-negative bacterium. The distinctive coloration helped eliminate the possibility of Gram-positive organisms among the potential unknowns.

The Gram stain is a crucial technique in microbiology as it provides valuable information about the structure of bacterial cell walls. The differentiation between Gram-positive and Gram-negative organisms aids in narrowing down the possibilities when identifying an unknown bacterium. The color change observed in the unknown organism, C14, suggests that it lacks a thick peptidoglycan layer in its cell wall.

Furthermore, the dark brick color observed in the initial observations and the pink color after the Gram stain can be indicative of specific biochemical characteristics and metabolic pathways of the bacterium. These observations will guide further research and testing to pinpoint the exact identity of the microorganism.

Future Experiments and Research:

To delve deeper into the identification process, additional experiments and research are essential. Biochemical tests such as catalase testing, oxidase testing, and fermentation assays can provide more insights into the metabolic capabilities of the bacterium. Moreover, molecular techniques like polymerase chain reaction (PCR) and DNA sequencing can help determine the genetic makeup of the unknown organism.

Calculation and Formula:

In this particular experiment, there are no specific calculations or formulas involved. The focus is on qualitative observations and the application of the Gram stain technique for identification purposes.

The Gram stain experiment proved to be a valuable tool in the identification process of the unknown microorganism, C14. The distinctive pink coloration indicated that the bacterium is Gram-negative, narrowing down the possibilities and eliminating Gram-positive organisms from consideration.

This laboratory experiment serves as a foundation for further investigations into the biochemical and genetic characteristics of the unknown organism. The findings pave the way for a comprehensive understanding of the bacterium's properties, leading to potential insights into diseases caused by similar organisms and the development of targeted treatments. The combination of careful observations, Gram stain analysis, and future experiments contributes to the ongoing efforts in microbiological research and identification.

Upon closer examination under a microscope, the unidentified organism exhibited a bacillus appearance with a configuration of either chains or clusters, though it was challenging to discern. No visible spores were observed. To aid in identification, a second experiment, the urease test, was conducted to assess the presence of the urease enzyme, which breaks down urea found in urine. Organisms within the Proteus genus typically test positive for urease, leading to an increase in pH and a color change in the pH indicator phenol red from yellow to red. However, when the urease test was performed on the unknown organism C 14, the media retained its yellow color, indicating the absence of the urease enzyme. This ruled out Proteus mirabilis as a potential candidate.

The unknown organism, labeled C 14, was identified as Serratia marcescens. Serratia marcescens is a Gram-negative bacillus with short rods, appearing pink or red at room temperature. Belonging to the Enterobacteriaceae family, it is naturally found in soil, water, and the intestines. S. marcescens is a human pathogen associated with nosocomial infections, including wound and urinary tract infections. Researching this bacterium proved challenging due to the similarity of articles and the lack of reputable sources.