Question

Which of the following is common to Azospirillum, Azotobacter, Anabaena, Nostoc, and Oscillatoria?
A) Prokaryotes
B) Nitrogen-fixers
C) Eukaryotes
D) (a) and (b)

Answer 1

Hint: Nitrogen fixation is a chemical process by which molecular nitrogen, with a strong triple covalent bond, in the air is converted into ammonia or related nitrogenous compounds, typically in soil or aquatic systems but also in industry.

Complete step-by-step answer: Azospirillum, Azotobacter, Anabaena, Nostoc, and Oscillatoria bacteria are all nitrogen-fixing biofertilisers. And all these are prokaryotes. The free-living bacteria are Azospirillum Azotobacter, Cyanobacteria, Anabaena, Nostoc, and Oscillatoria.
Hence the correct answer is option D.

Additional information Prokaryotes are organisms that do not lack a nucleus and other organelles. These are divided into two groups: Bacteria and Archaea. Mostly prokaryotes are small, single-celled organisms that have a relatively simple structure. Lacking internal membranes in prokaryotes differentiate them from eukaryotes. Their flagella are also different in design and movement from the flagella found on some eukaryotes. Anaerobes are the organisms that grow in the absence of free oxygen and those organisms that grow only when there is no oxygen are called obligate anaerobes. Microaerophiles are those organisms that can grow best in the presence of a low amount of oxygen.

Note: Biological nitrogen fixation in rhizobia occurs primarily in root or stem nodules and is induced by the bacteria present in legume plants. This symbiotic process has fascinated plants. Arbuscular mycorrhizal (AM) fungi are ubiquitous root symbionts that provide plants with nutrients or other benefits.