Question

Nitrifying bacteria are an example of:
A. Photoautotrophs
B. Photoheterotrophs
C. Chemoautotrophs
D. Chemoheterotrophs

Answer 1

Hint: The nitrifying bacteria are those that use atmospheric nitrogen and convert it into its organic forms to derive energy. Many of the nitrifying bacteria are used as biofertilizers as they advance the plant growth. They can be found as single living or colony-forming units.

Complete answer: The nitrifying bacteria are nitrogen-fixing bacteria. They are autotrophic organisms as they produce their food on their own by conversion of nitrogen into ammonia or other forms. They absorb the atmospheric nitrogen and then utilize it to obtain energy by oxidation processes. As nitrogen is a chemical and these bacteria are based on it for their nutritional needs, they are chemoautotrophs. They are present widely as soil bacteria. They can be found as free-living or in associations with host plants. Commonly the nitrifying bacteria are found associated with leguminous plants. These are plants having nodules in their roots. These nodules enclose various nitrifying bacterial colonies. Rhizobium is the most common example of nitrifying bacteria. It is found in legumes of chickpea, soybean, etc. They turn the root nodules pinkish in color and attach to them by flavonoids released by the roots. They secrete indole acetic acid that causes the root hairs to curl up. There are many chemoautotrophic microbes that depend on other chemicals like methane, carbon, hydrogen, etc. The nitrifying bacteria are beneficial to the environment also as they aid in the nitrogen cycle by converting nitrogen into ammonia, nitrates, nitrites, etc.
Hence, the right answer is option C.

Note: The chemoautotrophs are bacteria that can live in harshest conditions due to their tolerance to various chemicals. As they utilize chemicals to make their food they balance the ecosystems sustainably. Autotrophic organisms form the basis of the food chain. Thus, they are very beneficial.