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Microbes in Human Welfare Test - 61

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Microbes in Human Welfare Test - 61
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Weekly Quiz Competition
  • Question 1
    1 / -0
    Which of the following is not a biofertilizer?
    Solution
    A biofertilizer is a living microorganism or made up of dried microorganisms. It is applied to plant surfaces, or soil colonizes the rhizosphere or the interior of the plant and promotes growth by increasing the supply or availability of primary nutrients to the host plant. Biofertilizers such as Rhizobium, Azotobacter, Azospirilium, mycorrhiza and blue-green algae have been in use for a long time. 
    • Rhizobium inoculant is used for leguminous crops. Azotobacter can be used with crops like wheat, maize, mustard, cotton, potato, and other vegetable crops. 
    • Blue-green algae belonging to a general Cyanobacteria genus fix atmospheric nitrogen and are used as inoculations for paddy crop grown both under upland and lowland conditions. 
    • Mycorrhiza is a symbiotic association between a fungus and a plant. The Mycorrhiza plays a key role in selective absorption of immobile (P, Zn, and Cu) and mobile (S, Ca, K, Fe, Mn, Cl, Br, and N) elements to plants. These are available to plants in less amount.
    • Anabaena in association with water fern Azolla contributes nitrogen up to 60 kg/ha/season and also enriches soils with organic matter. 
    • Algae-fungi symbiosis is not used as biofertilizer because their symbiotic association forms lichens. 
    So, the correct answer is option D.
  • Question 2
    1 / -0
    Bio gas production from waste biomass with the help of methanogenic bacteria is a
    Solution
    The process of biogas production can be divided into four steps: hydrolysis, acetation, acidification, and methane formation.
    1. Hydrolysis: In the first step (hydrolysis), the organic matter is enzymolyzed externally by extracellular enzymes (cellulase, amylase, protease and lipase) of microorganisms. Bacteria decompose the long chains of the complex carbohydrates, proteins and lipids into shorter parts. 
    2. Acetation and 3. acidification: Acid-producing bacteria, involved in the second step, convert the intermediates of fermenting bacteria into acetic acid (CH$$_3$$COOH), hydrogen (H$$_2$$) and carbon dioxide (CO$$_2$$). These bacteria are facultatively anaerobic and can grow under acid conditions. To produce acetic acid, they need oxygen and carbon. They use the oxygen solved in the solution or bounded-oxygen. The acid-producing bacteria create an anaerobic condition which is essential for the methane producing microorganisms. 
    4. Methanogenesis: Methane-producing bacteria, involved in the third step, decompose compounds with a low molecular weight. They utilize hydrogen, carbon dioxide and acetic acid to form methane and carbon dioxide. 
    Thus, the correct answer is option A.
  • Question 3
    1 / -0
    Refer the given passage and answer the following questions.

    At present the primary nutrient which limits the agricultural yield is nitrogen (N). Some plants are capable to produce more$${ N_2}$$ than they consume. These plants show symbioticz relationship with $${N_2}$$-fixing bacteria such as Rhizobium. These bacteria produce root nodules in leguminous plants and convert atmospheric $${N_2}$$ into nitrogenous compounds. Rhizobium bacteria are gram negative bacteria, which show host specificity and fix $${N_2}$$ in the presence of a red pigment called leghaemoglobin. It protects nitrogen fixing enzyme nitrogenase from oxygen.

    Which of the following statements is incorrect?
    Solution
    Nitrogenase is a nitrogen fixing enzyme produced by nitrogen fixing bacteria. It is inactive in the presence of oxygen. Leghaemoglobin produced by the host cells acts as an oxygen scavenger and protects nitrogenase from oxygen.
  • Question 4
    1 / -0
    Refer the given passage and answer the following questions

    At present, the primary nutrient which limits the agricultural yield is nitrogen (N). Some plants are capable to produce more$${ N_2}$$ than they consume. These plants show a symbiotic relationship with $${N_2}$$-fixing bacteria such as Rhizobium. These bacteria produce root nodules in leguminous plants and convert atmospheric $${N_2}$$ into nitrogenous compounds. Rhizobium bacteria are gram-negative bacteria, which show host specificity and fix $${N_2}$$ in the presence of a red pigment called leghaemoglobin. It protects nitrogen-fixing enzyme nitrogenase from oxygen.

    Read the given statements and select the correct answer.

    Statement 1: Rhizobium bacteria can also live freely in the soil and carry out $${N_2}$$-fixation by themselves.
    Statement 2: Such Rhizobium bacteria are called free-living $${N_2}$$-fixing bacteria.
    Solution
    Rhizobium is a symbiotic bacterium which forms association with nodulated roots of different legumes. The bacterium obtains shelter and food from legume and in turn it performs nitrogen fixation inside nodules. Rhizobium lives in mutually beneficial association with other organisms and hence is known as symbiotic bacterium.
    So, the correct answer is 'Both statements 1 and 2 are false.'
  • Question 5
    1 / -0
    A free living nitrogen-fixing cyanobacterium, which can also form symbiotic association with the water fern Azolla is
    Solution
    Biofertilizers are the suspension of microorganism which mainly increases the growth of the plants. These secrete the growth promoting substances. Bio-fertilizers such as Rhizobium, Azotobacter, Azospirilium and blue-green algae (BGA) are used. Anabaena in association with water fern Azolla contributes nitrogen up to 60 kg/ha/season and also enriches soils with organic matter.
    So, the correct answer is option A.
  • Question 6
    1 / -0
    Which of the following is used as a biofertilizer for the cultivation of soybean crop? 
    Solution
    Rhizobium is a soil bacterium, that can colonize the legume roots and fix the atmospheric nitrogen symbiotically. They are known as the most efficient biofertilizer as per the quantity of nitrogen fixed concerned. It is used as a biofertilizer for raising soybean crops because soybean needs a large amount of nitrogen for protein formation and Thus, it is the richest source of protein.
    So, the correct answer is option C.
  • Question 7
    1 / -0
    Which of the following is a symbiotic nitrogen fixer?
    Solution
    Symbiotic nitrogen fixation is a process found in plants that harbor nitrogen-fixing bacteria within their tissues. Microorganisms, that can fix nitrogen include a diverse group of prokaryotes, cyanobacteria and diazotrophs, such as Azotobacteraceae, Rhizobia and Frankia. While the leguminous plants have the symbiotic association with Rhizobium for the fixation of nitrogen, Frankia is used by the non-leguminous plants in their symbiotic association. 
    So, the correct answer is 'Frankia'.
  • Question 8
    1 / -0
    Which of the following is the pair of biofertilizers for nitrogen fixation?
    Solution
    The term biofertilizers refer to the substance containing living or dried powder of microorganisms, it may be used to include all organic resources (manure) for plant growth which are rendered in an available form for plant absorption through microorganisms or plant associations or interactions. Biofertilizers are three types, nitrogen fixing bacteria, nitrogen-fixing cyanobacteria and mycorrhiza e.g., Rhizobium, Azotobacter, Azolla, Nostoc, Azospirilium and blue-green algae have been in use a long time. Thus, the correct answer is option A.
  • Question 9
    1 / -0
    Modern farmers can increase the yield of paddy upto 50% by the use of
    Solution
    Azolla pinnata is a species of fern known by several common names, including feathered mosquito-fern and water velvet. It is native to much of Africa, Asia from China to Japan, India and the Philippines and parts of Australia. The leaves contain the Anabaena azollae, which is a symbiont that fixes nitrogen from the atmosphere that the fern can use. This gives the fern the ability to grow in habitats that are low in nitrogen. Rice farmers sometimes, keep this plant in their paddies, because it generates valuable nitrogen via its symbiotic Cyanobacteria. So, modern farmers can increase the yield of paddy up to 50% by the use of Cyanobacteria in Azolla pinnata.
    Thus, the correct answer is option C.
  • Question 10
    1 / -0
    Which one of the following is not a biofertilizer?
    Solution
    Agrobacterium is not a biofertilizer. It causes crown gall disease in plants because of which it is most extensively used in biotechnology for the gene transfer and its expression. Nostoc, Rhizobium and Mycorrhiza is associated with roots of plants and converts the atmospheric Nitrogen into nitrites and nitrates and make it available for the plants.
    So, the correct answer is option A.
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