Studying of Unknown Microorganisms - Lab Report Example

The main motive to perform this study was to determine the presence of an unknown microorganism present in the provided sample. The study encompasses the classification of bacteria based on their chemical reactions, pH levels and osmoregulation. It is highly imperative to classify bacteria and identify microorganisms as they have enough potential to cause various diseases. Essentially, the identification process is highly pragmatic for the correct diagnosis and treatment. Identification of the bacteria provides a line of treatment. Thus, bacterial identification is the foremost step to accomplishing further investigation procedures. The three preliminary steps for the analysis procedure comprise principal isolation, staining and biochemical reactions as the sample may contain diverse microorganisms 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 populations 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 a thick peptidoglycan layer, it displays Gm +ve differential staining and if the microorganism possesses a thin or single layer of peptidoglycan, it takes up the counter stain Safranin of the Gram reaction. Counterstain 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 possessing thin peptidoglycan cell wall becomes colourless and therefore takes up the counter stain when stained with Safranin. The given sample displayed the Gm-ve character of the organism. The cellular morphology is rod-shaped (“Analytical solution for laboratories”; “Antimicrobial Therapy”; William, 2000).

Pink Color is observed on the culture plate, indicating that the unknown organism is lactose fermenting.

TSI contains glucose, sucrose and lactose together with iron and phenol red as a pH indicator. On fermentation of sugar, the pH of the medium changes indicated by the colour 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 also produces H2S (William, 2000).

TSI test is followed by the Imvic test, to test the ability of the strain to produce the enzyme tryptophanase. Unknown culture is unable to produce the enzyme typtophanase (William, 2000).

The unknown sample can produce H2S.

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 colour (William, 2000).

MIO is a semisolid medium which is used to test the motility of a given organism. The medium contains indole and ornithine. No change in color was observed as the medium remained yellow indicating a negative indole test. On the other hand, deep purple colour was obtained indicating a positive test for ornithine. Further, diffused growth was observed, which extended from the stab line forming cloudiness displaying the motile behaviour of the organism (William, 2000).

The unknown culture was grown on a sodium citrate medium containing ammonium salts as the nitrogen source and bromothymol blue as the pH indicator. The test displays the ability to generate citrate 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 colour from green (neutral) colour to blue (alkaline) (“Antimicrobial Therapy”).

Although the battery of test results concludes that the unknown organism is Citrobacter freundii, MR and VP displayed variation. Citrobacter freundii is MR positive and VP negative but the test results highlight the fact that the unknown sample is MR negative and VP positive. In the case of a positive MR test red colour is seen when a large quantity of acid is produced from the fermentation of glucose but if no significant acid is produced, the red colouration disappears which may give a false negative result. Further, the variation could be explained by the fact that glucose is converted into pyruvic acid, methyl red could detect the acid end products but if the pH is not altered significantly the test results show variation. Moreover, in the case of the VP test pyruvic acid condenses and is converted to Acetoin a carbonyl-containing molecule and acts as an electron acceptor. This is further converted to diacetyl and is detected by KOH and α-naphthol to form a red complex. If acetoin is formed, it may give a false positive VP result, as indicated in the present case with the unknown (William, 2000).

May cause urinary tract infections, sepsis and in certain cases it is also known to cause meningitis in infants. The bacterial species is known to possess an ampC gene in its plasmid, which provides resistance against ampicillin and other antibiotics. However, plasmid genes are also responsible for the alteration of certain characteristic features of the micro-organisms (“Antimicrobial Therapy”, William, 2000).