Friday, September 27, 2019

Microbiology lab report Example | Topics and Well Written Essays - 750 words

Microbiology - Lab Report Example Thus, bacterial identification is the foremost step to accomplish further investigation procedures. The three preliminary steps for the analysis procedure comprise principal isolation, staining and biochemical reactions as the sample may contain diverse microorganism belonging to different species. Identification is based on the kind of Gram reaction shown by the organism. This is the most significant staining, also called differential staining performed to categorize microbial population into two groups the Gram positive and Gram negative organisms. The reaction displays the characteristic of the cell wall of the bacterial species. If the bacterial species possess thick peptidoglycan layer, it displays Gm +ve differential staining and if the microorganism possesses thin or single layer of peptidoglycan, it takes up the counter stain Safranin of the Gram reaction. Counter stain Safranin is added to the reaction after washing the Gram stain with alcohol. Since, Gram positive organisms possessing thick peptidoglycan retains the stain while Gram negative organisms possess thin peptidoglycan cell wall becomes colorless and therefore takes up the counter stain when stained with Safranin. The given sample displayed Gm-ve character of the organism. The cellular morphology is rod shaped (â€Å"Analytical solution for laboratories†; â€Å"Antimicrobial Therapy†; William, 2000). Part 2 MAC plate- Pink Color is observed on the culture plate, indicating that the unknown organism is lactose fermenting. Triple sugar iron agar test (TSI)- TSI contains glucose, sucrose and lactose together with iron and phenyl red as a pH indicator. On fermentation of sugar, the pH of the medium changes indicated by the color change from red to yellow. Sodium thiosulfate present in the medium is reduced to H2S which in turn reacts with the ferric ions to give sulfide of iron which turns the medium black. In the present condition the isolate is capable of fermenting Lactose and al so produces H2S (William, 2000). Imvic test TSI test is followed by Imvic test, to test the ability of the strain to produce enzyme tryptophanase. Unknown culture is unable to produce the enzyme typtophanase (William, 2000). Hydrogen sulfide test The unknown sample is able to produce H2S. Urease test Urease enzyme is responsible for the hydrolysis of urea to generate CO2 and ammonia. The unknown culture shows the presence of urease enzyme as indicated by the pink color (William, 2000). Motility indole ornithine (MIO) test MIO is a semisolid medium which is used to test the motility of the given organism. The medium contains indole and ornithine. No change in color was observed as the medium remained yellow indicating negative indole test. On the other hand, deep purple color was obtained indicating positive test for ornithine. Further, diffused growth was observed, which extended from the stab line forming cloudiness displaying the motile behavior of the organism (William, 2000). Ci trate test The unknown culture was grown on sodium citrate medium containing ammonium salts as the nitrogen source and bromothymol blue as the pH indicator. The test displays the ability to generate citritase enzyme, responsible for the breakdown of citrate into oxaloacetate and acetate. Sodium bicarbonate and ammonia are produced during the process which changes the pH of the medium, indicated through the change in color from green (neutral) color to blue (alkaline) (â€Å"

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