I performed multiple tests for Bacillus cereus and I need help interpreting the

Question

I performed multiple tests for Bacillus cereus and I need help interpreting the results.
Anything helps. Thanks!
disclaimer: it's possible a few were false negatives or positives.

MORPHOLOGICAL FEATURES Gram Stain: Cell Morphology Cell Arrangement: Molk CULTURAL CHARACTERISTICS Colony Pigment: (+r-) Color: PHYSIOLOGICAL CHARACTERISTICS Osoluble? Catalase Test Result: Reagent Observation:u Interpretation of Result: Oxidase Test Result: Reagent: Observation: Interpretation of Result: Exoenzymes Test Observation Result Gelatin Interpretation of the above result Starch Interpretation of the above result Tributyrin Interpretation of the above result: Nitrate Reduction Result Observation after addition of Reagents A&B; (color): Interpretation of Result zinc (color):dark hMK TSIA Result Reported As: Observations: H:S? Interpret your results: Fermentation of Glu:Lac and/or Suc: : slant (color): :bull (color): gas produced (-or-) - Urea Hydrolysis Result: Observation: Interpretation of the Result:

Explanation / Answer

Bacillus cereus:

Morphological characteristics:

Gram Stain: Purple (Gram positive)

Cell arrangement: Single or in short chain

Cell morphology: Rod shaped

Cultural characteristics:

Colony pigment: Negative (On nutrient agar there is no pigment by the colony. But on selective media such as Mannitol Yolk Polymyxin (MYP) agar and Bacara agar it produces pink to orange opaque colonies.)

Colour: Grey white

H2O Soluble: Yes.

Physiological characteristics:

Catalase: Positive; Reagent: 3% H2O2;

Observation: bubbles are formed.

Interpretation: Catalase enzyme is produces by the bacteria which breaks down the H2O2 into water and oxygen, so bubbles of oxygen can be observed.

Oxidase: Neagtive

Reagent: 1% Kovac's reagent

Observation: No colour change

Interpretation: This is the test which is done to identify the presence of enzyme cytochrome c oxidase. If it is present then after reacting with the reagent it will give purple colour end product. Since this bacteria is oxidase negative so there is no formation of end product so no colour change.

Exoenzymes test: (Gelatine):

Observstion: Liquified gelatin is observed.

Result: Positive

Interpretation: this is the test for gelatin hydrolysis. Bacteria which produces the gelatinases enzyme that hydolysed the gelatin even at lower temperature and liquifies the gelatin. In this bacteria gelatinases is present so it hydrolyses the gelatin.

Exoenzyme test: (Starch):

Observation: Colour changes into blue- black.

Result: Positive

Interpretation: Since this bacteria produces amylase exoenzyme which cleaves starch into di and monosaccharide. So when iodine is added it turns into blue-black in the presence of starch.

Exoenzyme test ( Tributyrin)

Observation: Clear zone arround the colony.

Result: Positive

Interpretation: Since this bacteria produces lipase enzyme which hydrolyse the tributyrin into amino acids so clear zone surrounding the colony can be observed.

Nitrate Reduction:

Result: Positive

Colour after addition of the reagent A and B: Pink to Red.  

After addition of Zinc: Red

Interpretation: When sulfanilic acid is added, it will react with the nitrous acid to produce diazotized sulfanilic acid. This reacts with the ?-naphthylamine to form a red-colored compound. Therefore, if the medium turns red after the addition of the nitrate reagents, it is considered a positive result for nitrate reduction.

TSIA Test:

Observation H2S: -

Slant colour: Red, Butt Colour: Dark yellow. Gas production: No

Fermentation of glucose: Positive

Fermentation of Lactose/sucrose: Negative

Interpretation of result: since this bacteria can ferment glucose so the oxygen deficient butt will be yellow, but on the slant the acid will be oxidized to carbondioxide and water by the organism and the slant will be red.

Urea hydrolysis:

Observation: No pink colour colony is formed on urea agar, Yellow colour.

Result: negative

Interpretation: No production of the urease so no hydolysis of urea. so no colour change to pink.

Phenol red fermentation broth:

Glucose: Observation: yellow colour Result: positive

Interpretation: increased turbidity and color change from red to yellow, which indicates that acid has been produced anaerobically from glucose.

Lactose: Observation: Red colour

Result: Negative

Interpretation: NO colour change and presence of red colour means degradation of peptone, alkaline end product will generate and no fermentation of lactose.

Sucrose fermentation:

Observation: Red colour

Result: Negative

Interpretation: NO colour change and presence of red colour means degradation of peptone, alkaline end product will generate and no fermentation of Sucrose.

IMViC test:

Indole test: Negative

no formation of red colour ring after the addition of Kovac's reagent.

Methyl red: Negative

observation: yellow colour:

After the addition of methyl red no appearance of red colour.

Voges- Proskauer: Positive

occurance of brick red colour after the addition of 40% KOH.

Citrate utilization: Positive

occurance of blue colour indicates utilization of citrate.

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