Bacteriology of Water & Air MCQ Quiz | Environmental Microbiology

1. Which of the following is considered the most reliable indicator of recent fecal pollution in water?

• Escherichia coli
• Enterococcus faecalis
• Clostridium perfringens
• Pseudomonas aeruginosa

2. According to WHO standards for drinking water (potability), the count of coliform organisms should be:

• Less than 10 per 100 ml
• 1 per 100 ml
• Zero per 100 ml
• Less than 100 per 100 ml

3. What is the standard pore size of the filter used in the membrane filtration technique for water analysis?

• 0.22 µm
• 0.45 µm
• 1.0 µm
• 5.0 µm

4. The Most Probable Number (MPN) test for coliforms is based on which principle?

• Enzyme-substrate reaction
• Antibody-antigen binding
• Dilution to extinction
• Direct microscopic count

5. Which of the following water-borne diseases is caused by a spirochete?

• Typhoid fever
• Cholera
• Leptospirosis
• Giardiasis

6. The H2S strip test is a simple, low-cost method used to detect what in a water sample?

• Heavy metal contamination
• Viral presence
• High salinity
• Fecal contamination

7. The primary mechanism for bacterial removal in a slow sand filter is:

• Mechanical straining
• Chemical oxidation
• Biological action in the Schmutzdecke layer
• Adsorption to sand grains

8. Water disinfection using chlorine is generally less effective against which group of microorganisms?

• Gram-negative bacteria

• Protozoan cysts

• Enveloped viruses

• Yeasts

9. The Eijkman test is used to specifically detect:

• Total coliforms at 37°C
• Fecal coliforms (thermotolerant) at 44.5°C
• Clostridium perfringens spores
• Enterococci at 35°C

10. Legionella pneumophila, the causative agent of Legionnaires’ disease, is most commonly transmitted via:

• Contaminated food
• Direct person-to-person contact
• Inhalation of contaminated water aerosols
• Vector-borne transmission

11. Which organism is commonly considered an index of bacterial air pollution, especially in inhabited areas?

• Bacillus subtilis spores
• Micrococcus luteus
• Streptococcus pyogenes
• Escherichia coli

12. The sedimentation method (settle plate) for air sampling primarily collects:

• Only viral particles
• Small particles (<1 µm) effectively
• A known volume of air
• Larger particles (>5 µm) that settle by gravity

13. Which air sampling method involves drawing a known volume of air through a narrow slit onto a rotating agar plate?

• Impinger
• Membrane filter
• Slit sampler
• Settle plate

14. Droplet nuclei, which are crucial in airborne transmission of diseases like tuberculosis, are typically of what size?

• Greater than 100 µm
• 20-50 µm
• Less than 5 µm
• 0.5-1 µm

15. The Heterotrophic Plate Count (HPC) or Standard Plate Count (SPC) on a water sample measures:

• Only pathogenic bacteria
• Total coliform count
• The general population of viable aerobic/facultative anaerobic bacteria
• Anaerobic spore-forming bacteria

16. The typical IMViC test result for Escherichia coli is:

• –++
• ++–
• -+-+
• ++–

17. Breakpoint chlorination in water treatment is important because it ensures:

• Complete removal of water hardness
• Oxidation of all organic matter
• The formation of a stable free residual chlorine for effective disinfection
• The water has a pleasant taste and odor

18. Which of the following is an important airborne fungal pathogen, particularly dangerous for immunocompromised patients in hospital settings?

• Saccharomyces cerevisiae
• Aspergillus fumigatus
• Penicillium chrysogenum
• Candida albicans

19. Water purification using ultraviolet (UV) radiation is effective because UV light:

• Oxidizes the cell wall of bacteria
• Causes boiling of intracellular water
• Damages microbial DNA by forming pyrimidine dimers
• Denatures essential enzymes through heat

20. Biofilms in water distribution systems are a major public health concern primarily because they:

• Cause pipe corrosion and blockages
• Can harbor pathogenic bacteria and protect them from disinfectants
• Improve the taste and odor of the water
• Increase the pH of the water significantly

21. An organism that can survive in low-nutrient environments like distilled water and is a common cause of nosocomial infections from contaminated water sources is:

• Staphylococcus aureus
• Escherichia coli
• Pseudomonas aeruginosa
• Streptococcus pneumoniae

22. An impinger is a device used for air sampling where air is:

• Passed through a dry filter paper
• Allowed to settle on an agar plate by gravity
• Bubbled through a liquid collection medium
• Impacted directly onto a solid agar surface

23. Vibrio cholerae is the causative agent of cholera, a severe diarrheal disease. Its primary mode of transmission is:

• Airborne droplets

• Ingestion of contaminated water or food

• Mosquito bites

• Direct skin contact

24. A non-tuberculous mycobacterium frequently found in municipal water systems and associated with pulmonary disease, especially in immunocompromised individuals, is:

• Mycobacterium leprae
• Mycobacterium tuberculosis
• Mycobacterium avium complex (MAC)
• Mycobacterium bovis

25. The “Schmutzdecke” is a critical component for the functioning of which water treatment process?

• Rapid sand filtration
• Chlorination
• Reverse osmosis
• Slow sand filtration