Question

How many of these organisms are ${N_2}$ fixer autotrophs?
Azotobacter, chromium, Azospirillum , Rhodospirillum , Rhizobium , Nitrobacter , Aulosira , Nostoc , Osallatona.
A) three
B) four
C) five
D) six

Answer 1

It's basically found in neutral to alkaline nature soils, in aquatic environments, and on some plants. it's several metabolic capabilities, including atmospheric biological processes by conversion to ammonia.

Complete answer: Chromium:- chromium fixes the environment nitrogen.
Azospirillum :- it's a Gram-negative, microaerophilic, non-fermentative, and nitrogen-fixing bacterial genus from the family of Rhodospirillaceae.
Rhodospirillum :-Rhodospirillum maybe a purple nonsulfur bacteria which will grow aerobically or anaerobically. it's the facility to live through respiration, fermentation, photosynthesis, or photoautotrophic growth.
Rhizobium :-Rhizobium could also be a genus of Gram-negative soil bacteria that fix nitrogen. Rhizobium species form an endosymbiotic nitrogen-fixing association with roots of legumes and Parasponia.
Nitrobacter:-It is a chemoautotroph which is a negative bacteria. The name is derived from a Latin word that means alkalis. They fertilize by budding and nonmotile.
Aulosira :- it is a blue-green alga, which is usually found in paddy fields, different species of Aulosira are found on stones, mountains, lakes, etc.
Nostoc :- it can be found on different lands like moist rock, the bottom of lakes, and springs. It is a cyanobacterium that can be found in different habitats.

So , the correct answer is five i.e., options "C".

Note: nitrogen fixation is the basic cycle of converting molecular nitrogen in the air into ammonia. Atmospheric nitrogen is present in the form of dinitrogen, which is a reactive molecule that is useless in nature. It has to be converted and the same process is performed with the help of some bacterias.