Results

TEST	RESULTS
Growth On DTC agar. DTC agar was the enrichment media we chose to grow Serratia marcescens. The usually red colonies had a bluish tinge when seen against the background of the blue DTC agar. The colonies were pigmented only at room temperature or about 25 degrees Celsius.
Growth On T- Soy agar. At room temperature, Serratia marcescens grew as bright, glossy red colonies on the TSA plate. The agar was a general enrichment agar and was not specific for the growth of Serratia marcescens.
Growth on Macconkey's agar. Since the gram stain of Serratia marcescens revealed that the organism was a gram negative bacteria, MacConkey's agar served as a selective media. The organism grew as dark red colonies against the light pink background of the media.
Gram stain of Serratia marcescens. Gram staining a sample of the organism from a pure culture revealed that it was a gram negative rod.
Oxidation Fermentation tests. The organism was able to grow in both aerobic and anaerobic tubes. Acid was produced causing a change in the color of the pH indicator to yellow, but no gas was produced.
Mannitol Tubes. Serratia marcescens was able to metabolize mannitol to produce acid, but gas was not produced.
Enterotube – The tests and their results are as follows: - Glucose – Positive for the fermentation of glucose to produce acid, but negative for the production of gas. Lysine – Positive. The change in the color of the indicator from pale yellow to purple shows a change in the pH from acidic to alkaline conditions. The test shows the bacterial decarboxylation of lysine which results in the formation of alkaline end products. Ornithine – Positive. The test shows the bacterial decarboxylation of ornithine, which results in the formation of an alkaline end product. The pH indicator therefore undergoes a color change from pale yellow to purple. H2S production – Negative. This indicates that the organism is not capable to reducing sulfur containing products. Indol formation – Negative. This indicates that the organism does not have the enzyme tryptophanase to metabolize tryptophan. Adonitol – Negative. The organism does not ferment adonitol which results in the formation of acidic end products. Lactose – Negative. The organism is not capable of fermenting lactose. Arabinose – Negative. The organism is not capable of fermenting arabinose which results in the formation of acidic end products. Sorbitol – Positive. The organism is capable of fermenting sorbitol which results in the formation of acidic end products. Voges- Proskauer – Positive. The test detects the presence of aceylmethylcarbinol, an intermediate in the production of butyl glycerol in the fermentation of glucose. The presence was indicated by the development of a red color several minutes after the test was conducted. Dulcitol – Negative. The organism is not capable of fermenting dulcitol which results in the formation of acidic end products. Phenylalanine deaminase – Negative. The organism is not capable of producing pyruvic acid from the deamination of phenylalnine. Urea – Negative. The organism does not have the enzyme urease that is capable of hydrolyzing urea to ammonia. Citrate – Negative. The organism is not capable of utilizing citrate in the form of its sodium salt as the sole source of carbon.
Motility stab. The motility stab showed that the organism was motile since it moved upward to the surface of the tube.
Oxidase test	Negative. The sample on the cotton swab did not undergo a change in color several minutes after the reagent had been added.
Catalase test	Positive. Immediately after the hydrogen peroxide solution had been added to a sample of the organism, it produced effervescence.
Lactose test	Negative. The lactose tubes that were originally red due to the presence of the pH indicator did not undergo a change in color and there was no gas production. This indicted that the organism did not utilize lactose.