Question

Nitrate before adding zinc

Test tube 1 - E coli

Test tube 2 - E aerogenes

Test tube 3- P. hauseri

Test tube 4 - A. faecalis

Test tube 5 - K. pneumoniae

Test tube 6- S. aureus

Test tube 7 - S. epidermis

Test tube 8- E. faecalis

Test tube 9- K. rhizophila

Test tube 10- B. Subtilis  

Test tube 11 - C. xerosis

Test tube 12- B. cereus

Nitrate after addind zinc

Test tube 1 - E aerogenes

Test tube 2 - A. faecalis

Test tube 3 - E faecalis

Test tube 4 - Krhizophila

BA ETIJA

Answer 1

Answer-

According to the given question-

Nitrate reduction test- is performed to determine the facultative anaerobic microorganisms, carrying nitrate respiration. Complete oxidation of nitrate leads to gaseous end products such as N₂ or N₂O, with the help of additional enzymes nitrite reductase, nitrous reductase. but those microorganisms which can partially reduce the nitrate into nitrite have enzyme nitrate reductase, and this enzyme produced when the anaerobic condition, as well as nitrate, is present in the medium.

Two test reagents such as -

Nitrate reagent A - Sulfanilic acid

Nitrate reagent B- Dimethyl -alpha- napththylamine

After incubation, Nitrate reagent A and Nitrate reagent B was added - dark red color formation indicates the nitrite is formed, but if there is no color which means that either the microorganism completely reduced the nitrate into the gaseous end product such as N₂ or N₂O or unable to reduce nitrate into nitrite. this condition was checked by adding zinc dust in the medium in which no reaction was observed. if there is the formation of red color occurs which means that the unreduced nitrate is present in the medium and the organism was unable to reduce nitrate and if no color was observed, which means that the nitrate in the medium is not present and either it was exhausted and are completely used by the organism, which reduces it into gaseous products, such as N₂ or N₂O.

Here we have total 12 tubes were tested for nitrate reduction on the different organism-

Nitrate before adding zinc

Test tube 1 - E coli - red color was observed, dark red color formation indicates the nitrite is formed, which means that nitrate was partially reduced into nitrite.

Test tube 2 - E aerogenes - colorless, either the microorganism completely reduced the nitrate into the gaseous end product such as N₂ or N₂O or unable to reduce nitrate into nitrite.

Test tube 3- P. hauseri - red color was observed, dark red color formation indicates the nitrite is formed, which means that nitrate was partially reduced into nitrite.

Test tube 4 - A. faecalis - colorless, either the microorganism completely reduced the nitrate into the gaseous end product such as N₂ or N₂O or unable to reduce nitrate into nitrite.

Test tube 5 - K. pneumoniae - red color was observed, dark red color formation indicates the nitrite is formed, which means that nitrate was partially reduced into nitrite.

Test tube 6- S. aureus- red color was observed, dark red color formation indicates the nitrite is formed, which means that nitrate was partially reduced into nitrite.

Test tube 7 - S. epidermis- red color was observed, dark red color formation indicates the nitrite is formed, which means that nitrate was partially reduced into nitrite.

Test tube 8- E. faecalis - colorless, either the microorganism completely reduced the nitrate into the gaseous end product such as N₂ or N₂O or unable to reduce nitrate into nitrite.

Test tube 9- K. rhizophila - colorless, either the microorganism completely reduced the nitrate into the gaseous end product such as N₂ or N₂O or unable to reduce nitrate into nitrite.

Test tube 10- B. Subtilis - red color was observed, dark red color formation indicates the nitrite is formed, which means that nitrate was partially reduced into nitrite.

Test tube 11 - C. xerosis - red color was observed, dark red color formation indicates the nitrite is formed, which means that nitrate was partially reduced into nitrite.

Test tube 12- B. cereus - red color was observed, dark red color formation indicates the nitrite is formed, which means that nitrate was partially reduced into nitrite.

Nitrate after adding zinc

Test tube 1 - E aerogenes - red color occurs which means that the unreduced nitrate is present in the medium and the organism was unable to reduce nitrate

Test tube 2 - A. faecalis - red color occurs which means that the unreduced nitrate is present in the medium and the organism was unable to reduce nitrate

Test tube 3 - E faecalis - red color occurs which means that the unreduced nitrate is present in the medium and the organism was unable to reduce nitrate

Test tube 4 - Krhizophila - red color occurs which means that the unreduced nitrate is present in the medium and the organism was unable to reduce nitrate.