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  • Question
  • The diagnostic enzyme for nitrogen-fixing organisms is


  • Options
  • A. nitrogenase
  • B. nitrate reductase
  • C. nitrate oxidase
  • D. none of these

  • Correct Answer
  • nitrogenase 


  • Microbiology of Soils problems


    Search Results


    • 1. A heterocyst is

    • Options
    • A. a type of spore
    • B. a terminally differentiated cell that fixes nitrogen
    • C. the progenitor of cyanobacterial vegetative cells
    • D. a cell that carries out oxygenic photosynthesis
    • Discuss
    • 2. Some microorganisms have the ability to increase the nitrogen content of soils, are called as

    • Options
    • A. nitrogen fixation
    • B. denitrification
    • C. nitrification
    • D. all of these
    • Discuss
    • 3. Most soil protozoa are flagellates or amoebas, having their dominant mode of nitrogen as

    • Options
    • A. ingestion of bacteria
    • B. ingestion of mold
    • C. ingestion of fungi
    • D. all of these
    • Discuss
    • 4. The organisms responsible for the characteristic musty or earth odor of a freshly plowed field is/are

    • Options
    • A. Nocardia
    • B. Streptomyces
    • C. Micromonospora
    • D. all of these
    • Discuss
    • 5. Denitrification may be distinguished as

    • Options
    • A. dissimilative
    • B. assimilative
    • C. both (a) and (b)
    • D. blue baby syndrome
    • Discuss
    • 6. The groups of bacteria which have the ability to fix nitrogen from air to soil are

    • Options
    • A. symbiotic
    • B. nonsymbiotic
    • C. both (a) and (b)
    • D. none of these
    • Discuss
    • 7. The transformation of nitrates to gaseous nitrogen is accomplished by microorganisms in a series of biochemical reactions. The process is known as

    • Options
    • A. nitrification
    • B. denitrification
    • C. nitrogen fixation
    • D. ammonification
    • Discuss
    • 8. The population of algae in soil is __________ that of either bacteria or fungi.

    • Options
    • A. generally smaller than
    • B. generally greater than
    • C. equal to
    • D. none of these
    • Discuss
    • 9. The nonsymbiotic bacteria which fix nitrogen live in the soil independently are

    • Options
    • A. Azotobacter
    • B. Clostridium
    • C. considerably less important in comparison to the symbiotic bacteria
    • D. all of the above
    • Discuss
    • 10. For rapid decomposition by microbes, the substrate should have a C/N ratio of

    • Options
    • A. 10-20
    • B. 20-30
    • C. 30-40
    • D. 60-80
    • Discuss


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