Question

we were given an unknown bacteria to work with at lab. the results came and its written in the second observation. based on that observation i got to know that my unknown bacteria was Enterobacter aerogenes. so based on my second observation ive written, im to answer the last two columns( conclusion and comments)

Gram Negative Conclusion What does be your test result Comments List all possible organisms that match your Biochemical test and gram staining Theoretical Positive Second Observation results mean) Initial Observation Test Positive and formen Phenol Red Mannitol Phenol god postiel And posture Positive and Glucose Phenol Red Lactose nad poskus Yello Methyl Red 3 dopo Voges Proskauer Turgone Halow Negative Citrate Growth allowed Nitrate with Zositive Bubbles Strong Lotive yellow Catalase Negatie Urea Negative Gram+ Gram Stain N/A Gram - Growth Sterile pommented Loldless Agar Plate Sterile Motility motil Poshur Colorkess Negative Oxidase Purple positive Corker less negah Nitiche - Nitrogen Nog N2 organism reture Noz to Nitrocien

Answer 1

1. Phenol red mannitol

Result indicates drop in pH because of production of acid by the fermentation of sugar mannitol in the media. Bacteria can use mannitol for production of energy.

other examples: Citrobacter, E. coli, Klebsiella pneumoniae, Salmonella typhimurium

2. Phenol red glucose

Result indicates drop in pH because of production of acid by fermentation of sugar glucose in the media. Bacteria can use glucose for energy production.

other examples: all members of family Enterobacteriaceae

3. Phenol red lactose

Result indicates drop in pH because of production of acid by fermentation of sugar lactose in the media. Bacteria can use lactose for energy production.

other examples: Citrobacter, E. coli, Enterobacter, Klebsiella

4. Methyl red

Bacteria cannot metabolise glucose to pyruvic acid to further produce stable acid, thus pH is not reduced leading to yellow colour.

examples: Klebsiella pneumoniae

5. Voges-Proskauer (VP)

VP test is used to detect acetonin in bacterial broth culture. Test depends on digestion of glucose to acetyl methyl carbinol which in presence of oxygen and strong base produces diacetyl. Bacteria in medium does not produce acetonin.

examples: Streptococcus mitis, Citrobacter, Shigella, Yersinia, Edwardsiella, Salmonella, Vibrio furnissi

6. Citrate

This bacteria can grow in this medium producing citrate permease, capable of converting citrate to pyruvate. Pyruvate can enter organism's metabolic cycle for production of energy. Growth is indicative of utilization of citrate, an intermediate metabolite in Kreb's cycle.

Production of ammonia from ammonium salts increases alkalinity converting medium from green to blue.

examples : Salmonella, Edwardsiella, Citrobacter, Klebsiella, Enterobacter, Serratia, Provideneia

7. Nitrate

This test is based on ability to detect nitrite. When only nitrate is present red colour is produced. When nitrite is not detected it is necessary to test if organism has reduced nitrate to nitrite, which is done by adding Zn. Red colour indicates test organism is not capable of reducing nitrate.

examples: gram negative ENterobacteriaceae family members

8. Catalase

This bacteria produces catalase enzyme which catalyses the decomposition of hydrogen peroxide to water and oxygen.

examples: Staphylococci, Micrococci, Listeria, Cornybacterium diphtheriae, Nocardia, Pseudomonas, M. tuberculosis, Aspergillus

9. Urea

This bacteria does not hydrolyse urea to ammonia and CO₂ . Thus, medium is acidic producing no color change.

examples: Escherichia, Shigella, Salmonella

10. Gram stain

This bacteria has thinner peptidoglycan layer in the cell wall that allows crystal violet to wash out on addition of ethanol.

examples: Cynobacter, Green sulphur bacteria, most Proteobacteria

11. Agar

This bacteria produces non pigmented colorless colonies on agar plate.

example: Salmonella sp.

12. Motility

This bacteria is capable of motility via peritrichous flagella

examples: Listeria, Mycoplasma, Clostridium, Vibrio cholerae, Proteus sp., Spirochete

13. Oxidase

This bacteria does not produce cytochrome C oxidase, thus cannot use oxygen for energy production with electron transport chain.

examples: E. coli, Shigella, Salmonella, Enterobacter, Proteus, Yersinia