MICROBIOLOGY of SOILS Questions and Answers pdf :-

1. The nonsymbiotic bacteria which fix nitrogen live in the soil independently are

A. Azotobacter
B. Clostridium
C. considerably less important in comparison to the symbiotic bacteria
D. all of the above

Answer: D

2. Nitrogen fixation by the microorganisms can be detected by adopting the approach of

A. demonstrating growth in a nitrogen free medium
B. cultivating the microorganisms in the presence of nitrogen labeled with isotropic nitrogen
C. measuring15N2 by mass spectrometer
D. all of the above

Answer: D

3. Which of the following is not the biofertilisers producing bacteria?

A. Nostoc
B. Anabaena
C. Both (a) and (b)
D. Clostridium

Answer: D

4. Which of the following is capable of oxidizing sulfur to sulfates?

A. Thiobacillus thiooxidans
B. Desulfotomaculum
C. Rhodospirillum
D. Rhodomicrobium

Answer: A

5. Most soil protozoa are flagellates or amoebas, having their dominant mode of nitrogen as

A. ingestion of bacteria
B. ingestion of mold
C. ingestion of fungi
D. all of these

Answer: A

6. Which of the following microorganism use H2S as the electron donor to reduce carbon dioxide?

A. Chromaticum
B. Chlorobium
C. Both (a) and (b)
D. Rhodomicrobium

Answer: C

7. Nitrifying bacteria can not be isolated directly by the usual techniques employed to isolate hetrotrophic bacteria. The reasons may be due to

A. slow growth
B. medium growth
C. fast growth
D. none of these

Answer: A

8. Bacteria, as a group, are responsible for

A. nitrogen oxidation
B. sulfur oxidation
C. nitrogen fixation
D. all of these

Answer: D

9. The phenomenon of commensalism refers to a relationship between organisms in which

A. one species of a pair benefits
B. both the species of a pair benefit
C. one species of a pair is more benefited
D. none of the above

Answer: A

10. The population of algae in soil is __________ that of either bacteria or fungi.

A. generally smaller than
B. generally greater than
C. equal to
D. none of these

Answer: A

11. The transformation of nitrates to gaseous nitrogen is accomplished by microorganisms in a series of biochemical reactions. The process is known as

A. nitrification
B. denitrification
C. nitrogen fixation
D. ammonification

Answer: B

12. Nitrogen fixation refers to the direct conversion of atmospheric nitrogen gas into

A. ammonia
B. glucose
C. ATP
D. nitrate

Answer: A

13. The diagnostic enzyme for denitrification is

A. nitrate reductase
B. nitrate oxidase
C. nitro oxidoreductase
D. none of these

Answer: A

14. A heterocyst is

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

Answer: B

15. The groups of symbiotic bacteria, which have the ability to fix nitrogen

A. derive their food and minerals from the legume, and in turn they supply the legume with some or all of its nitrogen
B. grow together for a mutual benefit is called symbiosis and so these bacteria are called symbiotic nitrogen-fixing bacteria
C. these bacteria are from the genus, Rhizobium
D. all of the above

Answer: D

16. Nitrogen oxidation (nitrification)refers to the

A. conversion of ammonium ions into nitrates through the activities of certain bacteria.
B. changing of atmospheric nitrogen (N2) to nitrogen compounds
C. sulfur is oxidized to the sulfate form through Thiobacillus bacteria
D. none of the above

Answer: A

17. An example of a symbiotic nitrogen fixer is

A. Azotobacter
B. Beijerinckia
C. Clostridium
D. Rhizobium

Answer: D

18. Which of the following is correct?

A. Mycorrhizae are fungi that form a mutually beneficial (symbiotic) relationship with plant roots
B. The fungi aid in transmitting nutrients and water to the plant roots
C. The increased nutrient availability from mycorrhizae is thought to be due to the additional absorbing surface provided by the fungi
D. All of the above

Answer: D

19. In the process of nitrogen fixation, which of the following microorganism is involved?

A. Non symbiotic microorganisms only
B. Symbiotic microorganisms only
C. Non symbiotic and symbiotic microorganisms only
D. None of the above

Answer: C

20. Which of the following statement is not true about composition of biogas?

A. It is composed almost exclusively of methane and carbon dioxide
B. It also contains with traces of H2S, N2, H2and CO
C. It also contains with traces of O2 and Cl2
D. Both (a) and (b)

Answer: C

MICROBIOLOGY of SOILS Questions and Answers ::

21. The physical structure of soil is improved by the accumulation of

A. mold mycelium
B. minerals
C. water
D. all of these

Answer: A

22. __________ play a key role in the transformation of rock to soil.

A. Cyanobacteia
B. Pectin decomposing bacteria
C. Nitrifying bacteria
D. De-nitrifying bacteria

Answer: A

23. The groups of bacteria which have the ability to fix nitrogen from air to soil are

A. symbiotic
B. nonsymbiotic
C. both (a) and (b)
D. none of these

Answer: C

24. The nitrogenase consists of

A. dinitrogenase
B. dinitrogenase reductase
C. both (a) and (b)
D. none of these

Answer: C

25. The crops which are involved in nitrogen fixation are

A. alfalfa and clover
B. soybean
C. bean and lupine
D. all of these

Answer: D

26. Denitrification may be distinguished as

A. dissimilative
B. assimilative
C. both (a) and (b)
D. blue baby syndrome

Answer: C

27. The conversion of molecular nitrogen into ammonia is known as

A. nitrification
B. denitrification
C. nitrogen fixation
D. ammonification

Answer: C

28. The breakdown of cattle manure in biogas is accomplished by which of the following type of bacteria?

A. Hydrolytic
B. Transitional
C. methanogenic
D. All of these

Answer: D

29. Which of the following species of different genera of bacteria are not capable of transforming nitrate to nitrogen?

A. Achromobacter
B. Agrobacterium
C. Alcaligenes
D. None of these

Answer: D

30. Some microorganisms have the ability to increase the nitrogen content of soils, are called as

A. nitrogen fixation
B. denitrification
C. nitrification
D. all of these

Answer: A

31. Nitrogen fixation

A. changes the free nitrogen (N2) to a form usable by plants
B. especially changes nitrogen compounds, mostly amines such as NH2
C. both (a) and (b)
D. fix the free nitrogen (N2) by which it should not be usable by plants

Answer: C

32. For rapid decomposition by microbes, the substrate should have a C/N ratio of

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

Answer: C

33. Which are the main source of biofertilisers?

A. Cyanobacteria
B. Bacillus
C. Streptococcus
D. None of these

Answer: A

34. The organisms responsible for the characteristic musty or earth odor of a freshly plowed field is/are

A. Nocardia
B. Streptomyces
C. Micromonospora
D. all of these

Answer: D

35. Denitrification is

A. reduction of nitrate (NO3-) to nitrogen gas
B. reduction of nitrate to organic nitrogen compounds
C. both (a) and (b)
D. changing of atmospheric nitrogen (N2) to nitrogen compounds

Answer: C

36. Degree of compost maturity can be assesed by

A. infrared technique
B. germination test
C. both (a) and (b)
D. none of the above

Answer: C

37. The energy value of biogas is typically

A. 400-700 BTU/ft3
B. 1,000 BTU/ft3
C. 1500 BTU/ft3
D. more than 5000 BTU/ft3

Answer: A

38. The microbial ecosystem of soil includes

A. biotic components of soil
B. abiotic components of soil
C. biotic and abiotic components of soil
D. none of the above

Answer: C

39. Denitrification is carried out

A. usually by facultative anaerobes
B. predominantly by Pseudomonas spp
C. predominantly by Bacillus spp
D. all of the above

Answer: D

40. Which of the following soil microorganism is involved in the reduction of sulfates to H2S?

A. Thiobacillus thiooxidans
B. Desulfotomaculum
C. Rhodospirillum
D. Rhodomicrobium

Answer: B

41. The diagnostic enzyme for nitrogen-fixing organisms is

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

Answer: A

42. Which of the following fungi on infecting crop roots can improve their uptake of phosphorus and other nutrients?

A. Saccharomyces cerevisiae
B. VA Mycorrhiza
C. Candida torulopsis
D. Aspergillus niger

Answer: B

43. Syntrophism involves

A. exchange of nutrients between two species
B. exchange of nutrients among species
C. no exchange of nutrients between two species
D. no exchange of nutrients among species

Answer: A

44. Assimilative denitrification is done by

A. plants
B. fungi
C. prokaryotes
D. all of these

Answer: D

MICROBIOLOGY of SOILS Questions and Answers pdf free download ::