Question: 100% NCERT covered from Particular Keyword.Explanations are 100% from NCERT | [Difficult level: Easy] From NCERT NEET Derived Question.
Which one of the following organisms may respire in the absence of oxygen ?
(a) Azotobacter (b) Clostridium (c) Rhizobium (d) Lactobacillus
Ans: (b) Clostridium
free-living nitrogen-fixing aerobic microbes are Azotobacter and
Beijerinckia while Rhodospirillum is anaerobic and free-living. In addition,
a number of cyanobacteria such as Anabaena and Nostoc are also freeliving
nitrogen-fixers
Several types of symbiotic biological nitrogen fixing associations are known.
The most prominent among them is the legume-bacteria relationship.
Species of rod-shaped Rhizobium has such relationship with the roots of
several legumes such as alfalfa, sweet clover, sweet pea, lentils, garden pea,
broad bean, clover beans, etc. The most common association on roots is
as nodules. These nodules are small outgrowths on the roots. The microbe,
Frankia, also produces nitrogen-fixing nodules on the roots of nonleguminous
plants (e.g., Alnus). Both Rhizobium and Frankia are freeliving
in soil, but as symbionts, can fix atmospheric nitrogen.
