Q.1 Which of the following is a Gram-positive bacterium?
Escherichia coli
Staphylococcus aureus
Salmonella typhi
Neisseria gonorrhoeae
Explanation - Gram-positive bacteria have a thick peptidoglycan layer in their cell walls and retain the crystal violet stain, e.g., Staphylococcus aureus.
Correct answer is: Staphylococcus aureus
Q.2 Which microorganism is used in the production of alcohol?
Lactobacillus
Saccharomyces cerevisiae
Penicillium
Aspergillus niger
Explanation - Saccharomyces cerevisiae is a yeast that ferments sugars to produce ethanol and carbon dioxide.
Correct answer is: Saccharomyces cerevisiae
Q.3 Which of the following diseases is caused by a virus?
Tuberculosis
Malaria
Influenza
Ringworm
Explanation - Influenza is a viral respiratory infection caused by influenza viruses, while others are caused by bacteria, protozoa, or fungi.
Correct answer is: Influenza
Q.4 Which microbial process is used in yogurt production?
Fermentation
Photosynthesis
Nitrogen fixation
Decomposition
Explanation - Lactic acid bacteria ferment lactose in milk to produce lactic acid, giving yogurt its texture and taste.
Correct answer is: Fermentation
Q.5 Which of the following is an obligate anaerobe?
Clostridium tetani
Escherichia coli
Staphylococcus aureus
Bacillus subtilis
Explanation - Obligate anaerobes cannot survive in the presence of oxygen; Clostridium tetani grows only in oxygen-free environments.
Correct answer is: Clostridium tetani
Q.6 Which staining technique is used to identify Mycobacterium species?
Gram staining
Acid-fast staining
Endospore staining
Capsule staining
Explanation - Mycobacterium has a waxy cell wall with mycolic acid; acid-fast staining (Ziehl-Neelsen) is used for identification.
Correct answer is: Acid-fast staining
Q.7 Which of the following microbes is commonly used in the production of antibiotics?
Bacillus subtilis
Penicillium chrysogenum
Saccharomyces cerevisiae
E. coli
Explanation - Penicillium chrysogenum produces penicillin, one of the first and most widely used antibiotics.
Correct answer is: Penicillium chrysogenum
Q.8 What is the primary mode of reproduction in bacteria?
Binary fission
Budding
Spore formation
Fragmentation
Explanation - Bacteria reproduce asexually by binary fission, where one cell divides into two genetically identical cells.
Correct answer is: Binary fission
Q.9 Which virus is responsible for causing chickenpox?
Varicella-zoster virus
Measles virus
Hepatitis B virus
Influenza virus
Explanation - Varicella-zoster virus causes chickenpox and can later reactivate as shingles.
Correct answer is: Varicella-zoster virus
Q.10 Which microorganism is used in the production of citric acid industrially?
Aspergillus niger
Penicillium notatum
Saccharomyces cerevisiae
Clostridium acetobutylicum
Explanation - Aspergillus niger is a fungus widely used in industrial fermentation to produce citric acid.
Correct answer is: Aspergillus niger
Q.11 Which of the following is a nitrogen-fixing bacterium?
Rhizobium
Escherichia coli
Streptococcus
Clostridium tetani
Explanation - Rhizobium bacteria form symbiotic associations with leguminous plants to fix atmospheric nitrogen into ammonia.
Correct answer is: Rhizobium
Q.12 Which microorganism is used to produce acetone and butanol?
Clostridium acetobutylicum
Lactobacillus bulgaricus
Penicillium chrysogenum
E. coli
Explanation - Clostridium acetobutylicum is used in industrial fermentation for solvents such as acetone and butanol.
Correct answer is: Clostridium acetobutylicum
Q.13 Which is the smallest infectious agent?
Bacterium
Virus
Fungus
Protozoan
Explanation - Viruses are smaller than bacteria and require a host cell for replication.
Correct answer is: Virus
Q.14 Which bacterial structure helps in motility?
Pili
Flagella
Capsule
Cell wall
Explanation - Flagella are whip-like structures that enable bacterial movement in liquid environments.
Correct answer is: Flagella
Q.15 Which of the following is responsible for spoilage of milk?
Lactobacillus
Escherichia coli
Bacillus subtilis
Staphylococcus aureus
Explanation - Lactic acid bacteria like Lactobacillus ferment lactose, causing milk souring.
Correct answer is: Lactobacillus
Q.16 Which microorganism causes potato blight?
Phytophthora infestans
Aspergillus niger
Rhizobium
E. coli
Explanation - Phytophthora infestans is an oomycete responsible for late blight disease in potatoes.
Correct answer is: Phytophthora infestans
Q.17 Which viral genome is composed of RNA?
Herpes virus
Influenza virus
Adenovirus
Bacteriophage T4
Explanation - Influenza virus has a single-stranded RNA genome, unlike DNA viruses like Herpes virus or Adenovirus.
Correct answer is: Influenza virus
Q.18 Which of the following is used as a biofertilizer?
Rhizobium
Clostridium tetani
Staphylococcus aureus
Aspergillus niger
Explanation - Biofertilizers like Rhizobium enrich soil nitrogen and improve plant growth.
Correct answer is: Rhizobium
Q.19 Which of the following bacteria produces lactic acid?
Lactobacillus
Clostridium tetani
Salmonella typhi
Bacillus subtilis
Explanation - Lactobacillus converts lactose into lactic acid, used in fermented dairy products.
Correct answer is: Lactobacillus
Q.20 Which virus causes AIDS?
HIV
Hepatitis B virus
Influenza virus
Measles virus
Explanation - Human Immunodeficiency Virus (HIV) attacks the immune system leading to AIDS.
Correct answer is: HIV
Q.21 Which microorganism is used in the production of antibiotics like streptomycin?
Streptomyces
Bacillus subtilis
Saccharomyces cerevisiae
Aspergillus niger
Explanation - Streptomyces is a filamentous bacterium used industrially to produce antibiotics like streptomycin.
Correct answer is: Streptomyces
Q.22 Which microorganism is responsible for tetanus?
Clostridium tetani
Clostridium botulinum
Bacillus subtilis
Staphylococcus aureus
Explanation - Clostridium tetani produces tetanospasmin, the neurotoxin causing tetanus.
Correct answer is: Clostridium tetani
Q.23 Which of the following microorganisms is used in biogas production?
Methanogens
E. coli
Saccharomyces cerevisiae
Penicillium chrysogenum
Explanation - Methanogenic archaea produce methane from organic waste, which is used as biogas.
Correct answer is: Methanogens
Q.24 Which virus has a double-stranded DNA genome?
Herpes virus
Influenza virus
HIV
Poliovirus
Explanation - Herpes viruses are double-stranded DNA viruses, unlike RNA viruses like Influenza or Poliovirus.
Correct answer is: Herpes virus
Q.25 Which microorganism is used in the production of vinegar?
Acetobacter
Saccharomyces cerevisiae
Lactobacillus
Aspergillus niger
Explanation - Acetobacter oxidizes ethanol into acetic acid, which is the main component of vinegar.
Correct answer is: Acetobacter