Tag: bacteria; benefits and harmful effects

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Multiple choice botany bacteria bacteria - friend and foe useful and harmful bacteria bacteria; benefits and harmful effects

Souring of milk is due to

  1. Aerobic bacteria

  2. Anaerobic bacteria

  3. Both A and B

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Lactobacilli are anaerobic, rod shaped bacteria that produce lactic acid by anaerobic fermentation. They are responsible for digestion of milk sugar lactose into lactic acids at suitable temperatures which in turn add sour taste to milk. 

Therefore, the correct answer is option B.

Multiple choice botany bacteria bacteria - friend and foe useful and harmful bacteria bacteria; benefits and harmful effects

During sewage treatment, the microorganisms participate under which step?

  1. Primary

  2. Secondary

  3. Tertiary

  4. All of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Sewage treatment is a process in which the pollutants are removed. The ultimate goal of sewage treatment is to produce an effluent that will not impact the environment. In the absence of sewage treatment, the results can be devastating as sewage can disrupt the environment.
The general processes of sewage treatment are primary, secondary and tertiary treatment. Primary treatment involves physical separation of sewage into solids and liquid by using a settling basin. The liquid sewage is then transferred to secondary treatment which focuses on removing the dissolved biological compound by the use of 'micro-organisms'. The micro-organisms usually use aerobic metabolism to degrade the biological matter in the liquid sludge. Then tertiary treatment is required to disinfect the sewage so that it can be released into the environment. The solid sewage separated from primary treatment is transferred to a tank for sludge digestion which involves anaerobic degradation using micro-organisms.
Therefore, the correct answer is option B.
Multiple choice botany bacteria bacteria - friend and foe useful and harmful bacteria bacteria; benefits and harmful effects

Which organism is most useful for soil fertility?

  1. Algae

  2. Fungi

  3. Bacteria

  4. Bacteriophage
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Free-living and symbiotic nitrogen-fixing bacteria fix atmospheric inert nitrogen into biologically useful ammonia thereby adding nitrogen to the soil and increasing its fertility. Algae increase the organic carbon content of the soil upon their death. Mycorrhizae are the symbiotic fungi that reside in roots of higher plants and increase soil fertility by nitrogen fixation. Phages are the bacterial viruses that replicate within the bacterial cell with a polyhedral head, a helical tail and fibers for attachment to the host cell. Thus, the correct answer is option C.

Multiple choice botany bacteria bacteria - friend and foe useful and harmful bacteria bacteria; benefits and harmful effects

Antibiotics are mostly produced commercially from

  1. Immune host

  2. Parasitic fungi

  3. Saprophytic bacteria

  4. Viruses
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The antibiotics are substances produced by the natural metabolic processes of spore forming aerobic bacteria and fungi as their natural defence against other microorganisms. Immune host is the one which has acquired immunity against certain antigen by administration of antibiotics. It produces antibodies, not the antibiotics which makes option A incorrect. Commercial production of antibiotics by parasitic fungi needs their culture in live host cells which is a tedious and expensive process; Option B is incorrect. Saprophytic bacteria feed on dead and decaying organic matter and therefore, can easily be cultured on synthetic medium; option C is correct. Since, viruses are metabolically inactive outside the host cell and depend on host for their own nutritional requirements, they do not produce antibodies. Option D is incorrect. Thus, the correct answer is option C. 

Multiple choice botany bacteria bacteria - friend and foe useful and harmful bacteria bacteria; benefits and harmful effects

Which of the following considered as biofertilizer?

  1. Bacillus

  2. Polyporus

  3. Selaginella

  4. Azotobacter
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Biofertilizer is any living organism that imparts fertility to soil. Azotobacter is a free living aerobic rod shaped soil bacteria; it is a member of Gamma-proteobacteria and fix the atmospheric inter nitrogen into biologically usable ammonia and hence, serves as biofertilizer. 

Bacillus is a denitrification bacteria that carry out the final step in returning nitrogen back to the atmospheric reservoir. They reduce the nitrates into nitrogen thereby removing nitrogen from soil. 
Polyporus is a fungus which produces single cell protein; it does not add minerals/nutrients to soil. 
Selaginella is a fern which is used as ornamental plant and does not serve as biofertilizer. 
Thus, the correct answer is option D. 

Multiple choice botany bacteria bacteria - friend and foe useful and harmful bacteria bacteria; benefits and harmful effects

Nitrogen fixing bacteria converts

  1. N$ _2$ $\longrightarrow$ NH$ _3$
  2. NH$ _4^+$ $\longrightarrow$ Nitrates
  3. NO$ _2$ $\longrightarrow$ NO$ _3$
  4. NO$ _3$ $\longrightarrow$ N$ _2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • Conversion of atmospheric inert nitrogen into usable ammonia is termed as nitrogen fixation which is carried out by free-living symbiotic bacteria. 
  • They have a multisubunit enzyme complex, nitrogenase, which catalyzes the reduction of nitrogen to ammonia. The oxidation of ammonia (NH$ _4$) to nitrite (NO$ _2^-$) and finally to nitrate (NO$ _3^-$) is called as nitrification. It is carried out by nitrifying bacteria.
  • Nitrifier bacteria, Nitrobacter and Nitrococcus, convert nitrite into nitrate. Denitrification bacteria carry out the final step in returning nitrogen back to the atmospheric reservoir. They reduce the nitrates into nitrogen.

Thus, the correct answer is option A. 
Multiple choice botany bacteria bacteria - friend and foe useful and harmful bacteria bacteria; benefits and harmful effects

Free living nitrogen-fixing bacteria are found in 

  1. Air

  2. Soil

  3. Root nodules

  4. None of above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Earth’s atmosphere contains 78% nitrogen but it cannot be used by living organisms due to its inert form. This inert nitrogen is fixed into biologically active ammonia by free living or symbiotic bacteria and other microorganisms. The free living bacteria are present in soil where they perform nitrogen fixation; example: Azotobacter, Azospirillum and Clostridium. This makes option B correct. The finger like projections on roots of legumes, termed as root nodules, carries Rhizobium bacteria which in turn are responsible for nitrogen fixation. Legume get ammonia from Rhizobium and provide carbohydrates as an energy source to them; a symbiotic relation. This makes option C incorrect as root nodules harbour symbiotic bacteria. Nitrogen fixation does not occur in air as none of nitrogen fixing microbes are present in air; option A is incorrect. Thus, the correct answer is option B. 

Multiple choice botany bacteria bacteria - friend and foe useful and harmful bacteria bacteria; benefits and harmful effects

Which of the following is free-living aerobic non-photosynthetic nitrogen fixing bacterium?

  1. Rhizobium

  2. Azotobacter

  3. Nostoc

  4. Azospirillum
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Azotobacter is free-living aerobic non-photosynthetic nitrogen fixing bacterium which have wide variety of metabolic abilities, they fix atmospheric nitrogen as they produce nitrogenase enzyme and convert it to ammonia. They are free living in soil and do not associate as symbionts. 

So, the correct answer is option B.