Q.1 What term describes microorganisms that thrive in extreme environmental conditions?
Mesophiles
Thermophiles
Extremophiles
Psychrophiles
Explanation - Extremophiles are microorganisms that can survive in extreme conditions, such as very high or low temperatures, high salinity, or extreme pH.
Correct answer is: Extremophiles
Q.2 Which process involves the conversion of atmospheric nitrogen into ammonia by bacteria?
Denitrification
Nitrogen fixation
Ammonification
Nitrification
Explanation - Nitrogen fixation is carried out by certain bacteria, such as Rhizobium, which convert atmospheric nitrogen (N₂) into ammonia (NH₃), making it usable by plants.
Correct answer is: Nitrogen fixation
Q.3 Which type of symbiotic relationship is represented by mycorrhizal fungi associating with plant roots?
Parasitism
Mutualism
Commensalism
Competition
Explanation - In mutualism, both organisms benefit. Mycorrhizal fungi help plants absorb nutrients, while receiving carbohydrates from the plant.
Correct answer is: Mutualism
Q.4 What is the primary role of decomposer microorganisms in an ecosystem?
Produce oxygen
Break down organic matter
Fix nitrogen
Increase biodiversity
Explanation - Decomposers like bacteria and fungi break down dead organic matter, recycling nutrients back into the ecosystem.
Correct answer is: Break down organic matter
Q.5 Which microbial group is primarily responsible for methanogenesis in anaerobic environments?
Cyanobacteria
Methanogens
Nitrobacter
Actinomycetes
Explanation - Methanogens are archaea that produce methane (CH₄) under anaerobic conditions, such as in wetlands or the guts of ruminants.
Correct answer is: Methanogens
Q.6 Which term refers to the total microbial population in a specific environment?
Microbiome
Biome
Population density
Ecosystem
Explanation - The microbiome represents the entire community of microorganisms living in a particular environment or host.
Correct answer is: Microbiome
Q.7 Bioremediation primarily uses microorganisms to:
Produce antibiotics
Remove pollutants
Fix nitrogen
Enhance photosynthesis
Explanation - Bioremediation involves using microbes to degrade or detoxify environmental pollutants, like oil spills or heavy metals.
Correct answer is: Remove pollutants
Q.8 Which type of bacteria oxidizes ammonia to nitrite in the nitrogen cycle?
Nitrosomonas
Nitrobacter
Rhizobium
Azotobacter
Explanation - Nitrosomonas are nitrifying bacteria that convert ammonia (NH₃) to nitrite (NO₂⁻), a key step in nitrification.
Correct answer is: Nitrosomonas
Q.9 Which of the following is an example of a microbial biofilm?
Plaque on teeth
Soil fungi
Free-floating algae
Airborne bacteria
Explanation - Biofilms are communities of microorganisms attached to surfaces, embedded in a self-produced extracellular matrix, e.g., dental plaque.
Correct answer is: Plaque on teeth
Q.10 Which environmental factor most strongly affects microbial growth in aquatic systems?
Temperature
Salinity
pH
All of the above
Explanation - Microbial growth in aquatic environments is influenced by temperature, salinity, pH, and nutrient availability.
Correct answer is: All of the above
Q.11 Saprobes obtain nutrients from:
Living hosts
Dead organic matter
Sunlight
Inorganic minerals
Explanation - Saprobes, such as many fungi and bacteria, feed on dead and decaying organic matter, playing a critical role in nutrient recycling.
Correct answer is: Dead organic matter
Q.12 Which microbial process contributes directly to soil fertility by converting organic nitrogen to inorganic forms?
Denitrification
Ammonification
Methanogenesis
Photosynthesis
Explanation - Ammonification is the microbial process of converting organic nitrogen from dead organisms into ammonia, enriching soil nitrogen content.
Correct answer is: Ammonification
Q.13 Which of these microbes is commonly used in composting to degrade organic waste?
Lactobacillus
Pseudomonas
Actinomycetes
Methanogens
Explanation - Actinomycetes are filamentous bacteria that break down complex organic materials like cellulose and chitin in compost.
Correct answer is: Actinomycetes
Q.14 In freshwater ecosystems, which microbial group is primary for oxygen production?
Cyanobacteria
Methanogens
Nitrosomonas
Fungi
Explanation - Cyanobacteria are photosynthetic bacteria that produce oxygen and form the base of many aquatic food webs.
Correct answer is: Cyanobacteria
Q.15 Which type of microorganism is most abundant in the human gut microbiome?
Bacteria
Fungi
Viruses
Archaea
Explanation - Bacteria dominate the human gut microbiome, aiding digestion, vitamin production, and immune system regulation.
Correct answer is: Bacteria
Q.16 Which of the following is a common method to measure microbial diversity in soil?
Gram staining
16S rRNA sequencing
Optical microscopy
Catalase test
Explanation - 16S rRNA sequencing allows identification and classification of bacteria in environmental samples, assessing microbial diversity.
Correct answer is: 16S rRNA sequencing
Q.17 Which term describes bacteria that can use carbon dioxide as their sole carbon source?
Heterotrophs
Autotrophs
Saprophytes
Pathogens
Explanation - Autotrophic bacteria fix carbon dioxide to synthesize organic molecules for growth, unlike heterotrophs that rely on organic carbon.
Correct answer is: Autotrophs
Q.18 Which microbial activity is responsible for releasing nitrogen gas back into the atmosphere?
Nitrification
Denitrification
Ammonification
Nitrogen fixation
Explanation - Denitrifying bacteria convert nitrate (NO₃⁻) to nitrogen gas (N₂), completing the nitrogen cycle and returning nitrogen to the atmosphere.
Correct answer is: Denitrification
Q.19 Which group of microbes is mainly responsible for the degradation of petroleum pollutants in soil?
Methanogens
Hydrocarbon-degrading bacteria
Cyanobacteria
Actinomycetes
Explanation - Certain bacteria, like Pseudomonas, can metabolize hydrocarbons, playing a key role in bioremediation of oil-contaminated environments.
Correct answer is: Hydrocarbon-degrading bacteria
Q.20 Which of these environmental parameters directly influences microbial community structure in soil?
Moisture
pH
Temperature
All of the above
Explanation - Soil microbial communities are shaped by physical and chemical factors including moisture, pH, temperature, and nutrient availability.
Correct answer is: All of the above
Q.21 Which term describes microbes living on or in other organisms without causing harm or benefit?
Parasites
Commensals
Mutualists
Pathogens
Explanation - Commensal microorganisms coexist with hosts without affecting them significantly, unlike parasites or pathogens.
Correct answer is: Commensals
Q.22 Which microbial group is primarily involved in sulfur cycling in ecosystems?
Sulfur-oxidizing bacteria
Methanogens
Nitrosomonas
Lactobacillus
Explanation - Sulfur-oxidizing bacteria convert reduced sulfur compounds to sulfate, playing a key role in the sulfur cycle.
Correct answer is: Sulfur-oxidizing bacteria
Q.23 Which environmental microbiology technique is used to estimate viable microbial populations in water?
Plate count method
Gram staining
PCR
Flow cytometry
Explanation - The plate count method allows quantification of live microorganisms by counting colony-forming units (CFUs) after incubation.
Correct answer is: Plate count method
Q.24 Which of the following best describes eutrophication?
Oxygen depletion due to excess nutrients
Increase in soil pH
Reduction in microbial diversity
Formation of biofilms
Explanation - Eutrophication occurs when nutrient overload, especially nitrogen and phosphorus, causes algal blooms that deplete oxygen in water bodies.
Correct answer is: Oxygen depletion due to excess nutrients
Q.25 Which microorganism is commonly used in wastewater treatment for organic matter degradation?
Nitrosomonas
Activated sludge bacteria
Methanogens
Cyanobacteria
Explanation - Activated sludge contains mixed microbial communities that degrade organic pollutants in wastewater during treatment processes.
Correct answer is: Activated sludge bacteria