Question

Denitrification is carried out by
a. Pseudomonas and Nitrococcus
b. Nitrosomonas and Nitrobacter
c. Nitrosomonas and Nitrococcus
d. Pseudomonas and Thiobacillus

Answer 1

The microbial method of converting nitrate and nitrite to gaseous sources of nitrogen is denitrification. Denitrification is a reaction to changes in their immediate surroundings' oxygen concentration. Denitrifiers switch from aerobic respiration to anaerobic respiration only when oxygen is low, using nitrite as the electron acceptor.

Complete answer:

Nitrosomonas- Nitrosomonas is a genus of proteobacteria that oxidises ammonia. They are important players in wastewater treatment plants, where, by converting it to nitrite, they get rid of excess ammonia. Owing to its unusual metabolism, one species, Nitrosomonas europaea, is particularly important.

Nitrobacter- Nitrobacter plays an essential role in the nitrogen cycle in soil and aquatic environments by oxidising nitrite into nitrate. For their carbon needs, Nitrobacter fixes carbon dioxide through the Calvin cycle. Nitrobacter belongs to the Proteobacteria subclass.

Nitrococcus- Nitrococcus mobilis is only present and is a compulsory halophile in marine environments. It is in the form of a coccus and has a flagellum to assist in movement. This bacterium is a nitrifier, which means the nitrite is oxidised into nitrate. In marine settings, this is important in nitrogen cycling.

Pseudomonas- Pseudomonas denitrificans is a vitamin-producing species of polar flagellated, rod-shaped, gram-negative, aerobic, heterotrophic bacteria. It is one of the few microorganisms that, under aerobic conditions, can synthesise vitamins. Denitrification, i.e. the conversion back into atmospheric nitrogen of fixed nitrates, is carried out by denitrifying bacteria, e.g. Pseudomonas

Thiobacillus- Thiobacillus oxidises sulphate with thiosulfate and elemental sulphur, and A. Ferrooxidans oxidise the ferric shape of ferrous ions. A allows for this diverse oxidising capacity. High concentrations of several different ions, including iron, copper, cobalt, nickel, and zinc, are tolerated by ferrooxidans.

Hence, the correct answer is option (D).

Note: Denitrification occurs in tropical and temperate soils, in natural and intensively controlled habitats, in coastal and freshwater settings, in wastewater treatment plants, manure stores, and aquifers, and is a process common to both our terrestrial and aquatic ecosystems. It is a positive method in extracting nitrate from wastewater, but has a detrimental impact in extracting essential nitrogen fertiliser from the soil and releasing the greenhouse gas and the tropospheric pollutant.