201. Which biofertiliser would be most suitable for enriching nitrogen in the soil of a legume crop through symbiosis?
ⓐ. Azotobacter
ⓑ. Glomus
ⓒ. Rhizobium
ⓓ. Nucleopolyhedrovirus
Correct Answer: Rhizobium
Explanation: Legume crops commonly benefit from symbiotic nitrogen fixation by Rhizobium. The bacterium forms root nodules and supplies usable nitrogen to the plant. Azotobacter is free-living rather than symbiotic, while Glomus mainly helps with phosphorus uptake. The specific mention of legumes and symbiosis points to Rhizobium.
202. Which statement best distinguishes Azospirillum from Rhizobium?
ⓐ. Azospirillum is mainly a free-living nitrogen fixer, whereas Rhizobium is symbiotic in legume root nodules.
ⓑ. Azospirillum forms mycorrhiza, whereas Rhizobium is a cyanobacterium.
ⓒ. Azospirillum controls butterfly caterpillars, whereas Rhizobium controls plant pathogens.
ⓓ. Azospirillum produces biogas, whereas Rhizobium clarifies fruit juices.
Correct Answer: Azospirillum is mainly a free-living nitrogen fixer, whereas Rhizobium is symbiotic in legume root nodules.
Explanation: Azospirillum enriches soil nitrogen without forming the classic nodular symbiosis seen in legumes. Rhizobium, on the other hand, is identified by its association with legume root nodules. Both are useful as biofertilisers, but their mode of life differs. This makes them important comparison examples in agricultural microbiology.
203. Which option correctly matches a crop situation with the most suitable biofertiliser group?
ⓐ. Legume roots — baculoviruses
ⓑ. Paddy field — cyanobacteria
ⓒ. Drought-stressed crop — Saccharomyces
ⓓ. Root-pathogen problem — Methanobacterium
Correct Answer: Paddy field — cyanobacteria
Explanation: Cyanobacteria are especially valuable in paddy fields because many of them fix atmospheric nitrogen under such cultivation conditions. Baculoviruses are biocontrol agents, not biofertilisers. Saccharomyces is linked with fermentation, and Methanobacterium is linked with biogas. The field condition and desired benefit together identify cyanobacteria.
204. Which statement about cyanobacterial biofertilisers is correct?
ⓐ. They are used mainly for dissolving blood clots in agricultural animals.
ⓑ. They are important in paddy cultivation because they can fix nitrogen.
ⓒ. They form root nodules in leguminous plants like Rhizobium.
ⓓ. They work mainly by producing methane in the soil.
Correct Answer: They are important in paddy cultivation because they can fix nitrogen.
Explanation: Cyanobacteria such as Anabaena, Nostoc, and Oscillatoria are known for their nitrogen-fixing ability. This makes them particularly useful in paddy fields, where they contribute to soil fertility. They do not form legume nodules like Rhizobium. Their agricultural role is based on nutrient enrichment rather than methane production.
205. Which feature is not primarily associated with mycorrhiza?
ⓐ. Increased phosphorus absorption
ⓑ. Better tolerance to drought and salinity
ⓒ. Improved resistance to root-borne pathogens
ⓓ. Direct control of butterfly caterpillars
Correct Answer: Direct control of butterfly caterpillars
Explanation: Mycorrhiza helps plants mainly by improving nutrient uptake and tolerance to stressful conditions. It also supports resistance to root-borne pathogens and better overall growth. Control of butterfly caterpillars is associated with Bacillus thuringiensis, not with mycorrhiza. Caterpillar control belongs to biocontrol rather than mycorrhizal biofertilisation.
206. Which statement correctly compares biofertilisers and biocontrol agents in agriculture?
ⓐ. Biofertilisers always act through viral infection, whereas biocontrol agents always act through fungi.
ⓑ. Biofertilisers mainly improve nutrient availability, whereas biocontrol agents mainly reduce pest or pathogen damage.
ⓒ. Biofertilisers are used only in sewage treatment, whereas biocontrol agents are used only in biogas plants.
ⓓ. Biofertilisers and biocontrol agents are two names for the same microbial role.
Correct Answer: Biofertilisers mainly improve nutrient availability, whereas biocontrol agents mainly reduce pest or pathogen damage.
Explanation: Biofertilisers and biocontrol agents are both useful in agriculture, but they serve different purposes. Biofertilisers enrich soil nutrients or improve nutrient uptake by plants. Biocontrol agents protect crops by suppressing pests or disease-causing organisms. Keeping these roles separate is important in application-based questions.
207. A farmer wants a microbial association that improves phosphorus uptake and also helps plants withstand salinity and drought. Which property best identifies the chosen biofertiliser?
ⓐ. Formation of root nodules for nitrogen fixation
ⓑ. Species-specific infection of insect larvae
ⓒ. Symbiotic association between fungal hyphae and plant roots
ⓓ. Production of methane from dung slurry
Correct Answer: Symbiotic association between fungal hyphae and plant roots
Explanation: The description points to mycorrhiza, which is a symbiotic relationship between fungi and roots. This association enhances phosphorus uptake and improves tolerance to drought and salinity. It can also support protection against root-borne pathogens. The key identifying feature is the fungus-root partnership.
208. Which set includes only biofertilisers and excludes biocontrol agents?
ⓐ. Rhizobium, Azotobacter, and Glomus
ⓑ. Bacillus thuringiensis, Trichoderma, and NPV
ⓒ. Rhizobium, Bacillus thuringiensis, and Nostoc
ⓓ. Glomus, NPV, and Trichoderma
Correct Answer: Rhizobium, Azotobacter, and Glomus
Explanation: Rhizobium, Azotobacter, and Glomus all improve soil fertility or nutrient uptake and therefore belong to biofertiliser use. Bacillus thuringiensis, Trichoderma, and NPV are associated with biological control of pests or pathogens. The grouping depends on function rather than on whether the organism is bacterial, fungal, or viral. Biofertilisers and biocontrol agents therefore need to be kept distinct.
209. Which option correctly identifies a free-living bacterial biofertiliser?
ⓐ. Glomus
ⓑ. Nucleopolyhedrovirus
ⓒ. Trichoderma
ⓓ. Azospirillum
Correct Answer: Azospirillum
Explanation: Azospirillum is a free-living nitrogen-fixing bacterium found in soil. It improves soil nitrogen status without forming the classic legume root nodules seen with Rhizobium. The other options belong to fungal biofertiliser or biocontrol groups. This makes Azospirillum a clear example of a bacterial biofertiliser.
210. Which agricultural pair is not correctly matched?
ⓐ. Rhizobium — symbiotic nitrogen fixer
ⓑ. Glomus — control of butterfly caterpillars
ⓒ. Nostoc — cyanobacterial biofertiliser
ⓓ. Azotobacter — free-living nitrogen fixer
Correct Answer: Glomus — control of butterfly caterpillars
Explanation: Glomus is associated with mycorrhiza and helps in phosphorus uptake, not caterpillar control. Butterfly caterpillar control is linked with Bacillus thuringiensis. The other three pairs are correctly matched with their agricultural roles. The mismatch comes from confusing biofertilisation with biocontrol.
211. Which statement best describes the contribution of mycorrhiza to plant health?
ⓐ. It improves phosphorus uptake and helps resist root-borne pathogens.
ⓑ. It converts palm sap into a fermented drink.
ⓒ. It dissolves blood clots inside plant vessels.
ⓓ. It produces methane in waterlogged crop fields.
Correct Answer: It improves phosphorus uptake and helps resist root-borne pathogens.
Explanation: Mycorrhiza is a fungus-root association that improves nutrient absorption, especially phosphorus. It also helps plants tolerate root-borne pathogens and stressful soil conditions more effectively. Its role is therefore both nutritional and protective.
212. Which set contains only free-living nitrogen-fixing biofertilisers?
ⓐ. Rhizobium and Glomus
ⓑ. Azospirillum and Azotobacter
ⓒ. Nostoc and Rhizobium
ⓓ. Glomus and Anabaena
Correct Answer: Azospirillum and Azotobacter
Explanation: Azospirillum and Azotobacter are both free-living bacteria that enrich soil nitrogen. Rhizobium is symbiotic in legume nodules, while Glomus is a fungal mycorrhizal partner. Nostoc is a cyanobacterial biofertiliser, so it does not form a pair of free-living bacterial nitrogen fixers with Rhizobium. The correct answer therefore identifies the free-living bacterial pair.
213. A rice field requires a biofertiliser especially suited to flooded conditions and known for nitrogen fixation. Which option is most appropriate?
ⓐ. Trichoderma
ⓑ. Cyanobacteria such as Anabaena and Nostoc
ⓒ. Saccharomyces cerevisiae
ⓓ. Bacillus thuringiensis
Correct Answer: Cyanobacteria such as Anabaena and Nostoc
Explanation: Paddy fields are especially suited to cyanobacterial biofertilisers because many cyanobacteria can fix atmospheric nitrogen in such environments. Anabaena and Nostoc are standard examples. Their contribution improves soil fertility and supports rice cultivation. The other organisms listed serve different roles such as fermentation or pest control.
214. Which statement best compares Rhizobium and cyanobacterial biofertilisers?
ⓐ. Both are fungal partners that improve phosphorus absorption.
ⓑ. Rhizobium and cyanobacteria are both used mainly as insect pathogens.
ⓒ. Rhizobium works in legume root nodules, whereas cyanobacteria are important biofertilisers in paddy fields.
ⓓ. Rhizobium produces methane, whereas cyanobacteria clarify fruit juices.
Correct Answer: Rhizobium works in legume root nodules, whereas cyanobacteria are important biofertilisers in paddy fields.
Explanation: Rhizobium is identified by its symbiotic association with legume roots, while cyanobacteria are especially associated with paddy-field fertility. Both help improve nitrogen nutrition, but they operate in different agricultural settings. This comparison highlights crop-specific use of biofertilisers. The distinction is based on habitat and mode of association.
215. Which option best represents the broad welfare role of microbes in agriculture?
ⓐ. They are useful only when converted into chemical pesticides.
ⓑ. They contribute only through alcoholic fermentation of crop products.
ⓒ. They enrich soil fertility as biofertilisers and also protect crops as biocontrol agents.
ⓓ. They increase crop growth only by producing antibiotics in leaves.
Correct Answer: They enrich soil fertility as biofertilisers and also protect crops as biocontrol agents.
Explanation: In agriculture, microbes help in more than one way. Some improve soil nutrients or nutrient uptake, while others suppress pests and pathogens. These two roles together support healthier crop production with reduced dependence on harsh chemical inputs. This makes microbes valuable partners in sustainable farming.
216. Which statement is most accurate about Glomus-based mycorrhiza?
ⓐ. It is mainly used to ferment bread dough.
ⓑ. It is a bacterium that forms nodules on legume roots.
ⓒ. It is a viral agent used in integrated pest management.
ⓓ. It is a fungal association that improves phosphorus uptake and stress tolerance.
Correct Answer: It is a fungal association that improves phosphorus uptake and stress tolerance.
Explanation: Glomus forms mycorrhizal associations with plant roots. Through this relationship, plants gain better phosphorus absorption and improved tolerance to drought, salinity, and root-borne pathogens. That is why mycorrhiza is such an important fungal biofertiliser example.
217. Which pair best illustrates two different useful applications of the same microbe, Saccharomyces cerevisiae?
ⓐ. Bread making and ethanol production
ⓑ. Curd formation and root nodule formation
ⓒ. Swiss cheese formation and butyric acid production
ⓓ. Penicillin production and statin production
Correct Answer: Bread making and ethanol production
Explanation: Saccharomyces cerevisiae is a versatile yeast used in more than one useful process. In bread making, it helps dough rise through fermentation, while in industrial and beverage contexts it produces ethanol from sugars. The same microbe can therefore be used for different outcomes depending on the substrate and purpose. This makes it one of the best examples of a widely useful industrial and household microbe.
218. Which statement correctly distinguishes beer from rum?
ⓐ. Beer is distilled after fermentation, whereas rum is not distilled.
ⓑ. Beer is produced without distillation, whereas rum is obtained after distillation of fermented broth.
ⓒ. Beer is formed by lactic acid bacteria, whereas rum is formed by methanogens.
ⓓ. Beer is a fungal cheese product, whereas rum is a bacterial acid product.
Correct Answer: Beer is produced without distillation, whereas rum is obtained after distillation of fermented broth.
Explanation: Beer belongs to the undistilled group of alcoholic beverages. Rum, in contrast, is obtained after a fermented broth undergoes distillation. Both involve fermentation at an earlier stage, but only one includes the additional distillation step. This processing difference is the key basis of comparison.
219. Which option is correctly matched throughout?
ⓐ. Citric acid — Acetobacter aceti; acetic acid — Aspergillus niger; ethanol — Lactobacillus
ⓑ. Butyric acid — Saccharomyces cerevisiae; lactic acid — Clostridium butylicum; citric acid — Streptococcus
ⓒ. Citric acid — Aspergillus niger; acetic acid — Acetobacter aceti; ethanol — Saccharomyces cerevisiae
ⓓ. Lactic acid — Monascus purpureus; butyric acid — Rhizobium; acetic acid — Glomus
Correct Answer: Citric acid — Aspergillus niger; acetic acid — Acetobacter aceti; ethanol — Saccharomyces cerevisiae
Explanation: Industrial microbiology depends heavily on correct matching of microbes with their major products. Aspergillus niger is used for citric acid, Acetobacter aceti for acetic acid, and Saccharomyces cerevisiae for ethanol. Each microbe is selected because of a characteristic metabolic output. Product-source mapping is therefore a central idea in industrial microbial use.
220. A patient has a dangerous blood clot blocking a vessel. Which source-product pair is most directly relevant for treatment?
ⓐ. Monascus purpureus — statin
ⓑ. Trichoderma polysporum — cyclosporin A
ⓒ. Aspergillus niger — citric acid
ⓓ. Streptococcus — streptokinase
Correct Answer: Streptococcus — streptokinase
Explanation: Streptokinase is the microbial product used as a clot buster. It is obtained from certain species of Streptococcus and is medically important because it helps dissolve blood clots. The other products listed serve different purposes such as cholesterol lowering, immunosuppression, or acid production. The clinical clue here is clot removal.
