Answer to Question #279643 in Microbiology for Assign

Question #279643

Do you think bacteroid is indifferent from a typical Rhizobium? If yes/no- justify your answer.

2. Write down the role of flavonoids and leg hemoglobin in the infection process by Rhizobia.

3. What do you understand by oxidation and reduction reaction? Write down the different types of the oxidation and reduction reactions (with the name of end product) that occur in the sulfur cycles?

4. Soil bacteria conduct N-fixation by two different ways, write down the similar and different characteristics between these N-fixation processes?

Expert's answer
  1. Yes. Rhizobium is a bacteroid because, After infecting the host cell, the bacteria differentiate into a distinct bacteroid form, which is able to fix nitrogen.
  2. Flavonoids play an essential role in rhizobium-legume symbiosis as chemoattractant and nod gene inducers . They are suggested to act on mycorrhization by stimulating germination of spores and hyphal growth.
  3. Oxidation reaction: The reaction in which oxygen is gained or hydrogen is lost, is called oxidation reaction. e.g. 2Cu+O2​heat ​2CuO. Reduction reaction. The reaction in which hydrogen is gained or oxygen is lost, is called reduction reaction.

Sulfate reduction is a vital mechanism for bacteria and archaea living in oxygen-depleted, sulfate-rich environments.

Sulfate reducers may be organotrophic, using carbon compounds, such as lactate and pyruvate as electron donors, or lithotrophic, and use hydrogen gas (H2) as an electron donor.

Before sulfate can be used as an electron acceptor, it must be activated by ATP -sulfurylase, which uses ATP and sulfate to create adenosine 5′-phosphosulfate (APS).

Sulfate-reducing bacteria can be traced back to 3.5 billion years ago and are considered to be among the oldest forms of microorganisms, having contributed to the sulfur cycle soon after life emerged on Earth.

Toxic hydrogen sulfide is one waste product of sulfate-reducing bactera, and is the source of the rotten egg odor.

Sulfate-reducing bacteria may be utilized for cleaning up contaminated soils.


  • Nitrogen Fixation by Free-Living Heterotrophs
  • Associative Nitrogen Fixation
  • Symbiotic Nitrogen Fixation

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