Microbiology online test focuses on “Determining Sanitary Quality of Water”.
1. Which of the following forms of water is the most contaminated?
A. Underground water
B. Rainwater
C. Surface water
D. Water stored in ice caps
Answer: C
Clarification: Surface water should not be used for drinking purposes unless it is subjected to purification since there is constant danger of contamination and consequent transmission of disease.
2. Alum is used for which of the following purification process?
A. Sedimentation
B. Filtration
C. Disinfection
D. Ozonation
Answer: A
Clarification: Sedimentation is enhanced by addition of alum (aluminum sulphate) at the treatment plant, which produces a sticky flocculent precipitate.
3. The potability of water can be checked by sanitary surveys.
A. True
B. False
Answer: B
Clarification: Sanitary surveys reveal whether water is being produced under conditions in which potable water would ordinarily be produced. However, potability can be determined only by chemical and bacteriological laboratory tests.
4. The coliform group of bacteria includes all the __________________ bacilli.
A. aerobic
B. anaerobic
C. aerobic, non-sporulating
D. aerobic, gram-negative, non-sporulating
Answer: D
Clarification: The coliform group of bacteria includes all the aerobic and facultatively anaerobic, gram-negative, non-sporulating bacilli that produce acid and gas from the fermentation of lactose.
5. Which of the following organism does not belong to coliform group of bacteria?
A. Salmonella
B. Serratia
C. Enterobacter
D. Proteus
Answer: C
Clarification: Coliform group of bacteria consists of E.coli and Enterobacter aerogenes. All others belong to the enteric group.
6. Coliforms are natural inhabitants of the large intestine of human and animals.
A. True
B. False
Answer: A
Clarification: Coliforms, fecal streptococci and Clostridium perfringens are normal inhabitants of the large intestine of humans and other animals and are consequently present in feces.
7. Which of the following acts as a carbon source for Enterobacter aerogenes?
A. Peptone
B. Sodium citrate
C. Yeast extract
D. Tryptone
Answer: B
Clarification: Enterobacter aerogenes will grow in a chemically defined medium in which sodium citrate is the only carbon compound as it is capable of utilizing it.
8. What will be the plate count of good quality water?
A. 10 per ml
B. 50 per ml
C. 100 per ml
D. 1000 per ml
Answer: C
Clarification: In the standard plate count method, water of good quality is expected to give a low count, less than 100 per ml.
9. Among the following which microorganism acts as a representative of fecal streptococci group?
A. Streptococcus faecalis
B. Streptococcus bovis
C. Streptococcus equinus
D. Streptococcus faecium
Answer: A
Clarification: Streptococcus faecalis is representative of the fecal streptococci group and are abundantly present in the large intestine of humans. Their occurrence in water is indicative of fecal pollution.
10. Thiobacillus can produce an acidity in the range of pH __________
A. 7
B. 5
C. 3
D. 1
Answer: D
Clarification: Organisms of the genus Thiobacillus oxidize elemental sulphur to sulphuric acid and can produce acidity in the range of pH 1.
11. In which of the following organism does iron secreted to form stalks or ribbons attached to the cell?
A. Sphaerotilus
B. Gallionella
C. Thiobacillus
D. Streptococcus
Answer: B
Clarification: Some iron bacteria such as Gallionella transform soluble compounds of iron to insoluble compounds of iron which are secreted to form stalks or ribbons attached to the cell.
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