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Examples Of Unknown Lab Report

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Unknown Lab Report
Abiola Oyewumi
March 16, 2015
Unknown #16
Abstract
An experiment was conducted to determine which of the following unknown bacteria was in test tube number 16: Escherichia coli, Enterobacter aerogenes, Klebsiella pneumoniae, and Salmonella typhimurium. Biochemical tests were used to help identify the unknown bacteria. The Citrate test, Urease test, Triple Sugar Iron Agar test, Voges-Proskauer test, and Methyl Red test were the biochemical tests used in this experiment. The T-Streak method was also used to ensure that pure colonies were created. The results of the biomedical test concluded that the unknown bacteria number 16 was in fact E. aerogenes.
Introduction
Gram-negative and Gram-positive bacteria are similar but also …show more content…

The reason the Gram-negative bacteria stains red or pink is because of the peptidoglycan layer (Leboffe and Pierce 105). Unlike Gram-positive bacteria, Gram-negative bacteria have a very thin peptidoglycan layer. The Gram-positive bacteria thick peptidoglycan layer is able to hold the primary stain, crystal violet, which causes it to stain purple (Bacterial Morphology). When the primary stain is placed on the Gram-negative bacteria, the thin peptidoglycan layer is not able to preserve the primary stain and is washed away throughout the gram stain procedure. Gram-positive bacteria contains teichoic acid which give the bacteria a negative charge (Bacterial Morphology). Gram-negative bacteria also have a negative charge but get the charge from lipopolysaccharides (Bacterial Morphology). For this experiment, biochemical tests were utilized to help determine which of the following four bacteria were in the unknown test tube number 16: E. coli, E. aerogenes, K. pneumoniae, and S. typhimurium. The unknown bacteria was also inoculated and placed on a TSA plate using the T-Streak method to verify that isolated colonies could be obtained. The biochemical tests that were used were the Citrate test, Methyl Red test, Voges-Proskauer test, Urease test, Sulfur Indole Motility test, and Triple Sugar Iron Agar test. The biochemical tests helped differentiate …show more content…

The medium did not change color after the Kovac reagent was added. Thus, the microorganism was not able to reduce sulfur to hydrogen sulfide (Leboffe and Pierce 202). The lack of blackening in the medium confirms the negative results. The organism tested negative for indole production. If indole was produced, dimethylaminobenzaldehyde (DMABA), which is in the reagent, would reacts with any indole that is present in the media (Leboffe and Pierce 202,203). Therefore it can be concluded that indole wasn’t produced and that the organism did not possess tryptophanase and could not hydrolyze tryptophan into pyruvate, ammonia, and indole. However, the organism tested positive for motility. After the incubation period, the growth of the organism radiating in all directions in the test tube (Leboffe and Pierce 203). The stab line was no longer visible. The positive motility results imply that the microorganism is cable of moving

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According to the series of test that my group ran for our unknown specimen, we had a match with the bacteria known as Alcaligenes Faecalis. This bacterium belongs to one of the major group of gram-negative bacteria (Phylum Proteobacteria). Alcaligenes Faecalis (Genus, species) is a rod shaped (bacillus), 0.5-1.2 x 1.0-3.0 µm, round with scalloped margin (colony configuration growth), motile (with one to nine peritrichous flagella), gram-negative, non-fermentative bacteria, obligate aerobic, having oxygen as the principal terminal electron acceptor in the electron transport chain (ETC). We consider we have a match with the species Alcaligenes Faecalis because of the following reasons: Fermentation tests performed (Durham sugars) were negative, which indicate that our bacteria use a different metabolic means for growth (non-fermentative gram-negative bacteria).

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Initial Streaking of Unknown in First lab Period The first lab period of this experiment an unknown was assigned. The unknown that corresponds to this lab report is unknown #19. The unknown was cultured during the first lab experiment using TSA, blood agar, MacConkey as the media. The plates were cultured using the streak plate technique.

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