Unit 6: Water and Food Microbiology - Practice Quiz

1 Which group of microorganisms commonly indicates bacterial pollution in water?

2 What is a major source of bacterial pollutants in drinking water?

3 Which organism is commonly used as an indicator of fecal contamination?

4 Coliform bacteria are generally described as Gram-negative bacteria that can ferment which sugar?

5 Which of the following is a non-coliform microorganism?

6 What is sewage primarily composed of?

7 Which type of material is commonly present in sewage?

8 Which microorganisms are commonly found in domestic sewage?

9 What is the main purpose of sewage treatment?

10 Which process is commonly used during sewage treatment to allow solids to settle?

11 Which method can be used to disinfect treated sewage?

12 Which group includes important microorganisms found in foods?

13 Which yeast is widely used in bread making?

14 What gas is produced by yeast during bread fermentation?

15 Which bacterial group is commonly used to make yogurt?

16 Which bacterium is commonly associated with food poisoning?

17 Molds belong to which group of organisms?

18 Which food is commonly affected by mold growth?

19 What is the main purpose of food preservation?

20 Which preservation method uses low temperatures to slow microbial growth?

21 A water sample contains high levels of organic waste and bacteria that rapidly consume dissolved oxygen. Which change is most likely to occur first in the receiving stream?

22 Why are coliform bacteria commonly used as indicators of drinking-water contamination?

23 A water sample tests positive for total coliforms but negative for fecal coliforms. What is the best interpretation?

24 Which characteristic most helps distinguish fecal coliforms from many non-coliform bacteria during water testing?

25 A rural well is located near a leaking septic tank. Which group of bacteria is the most appropriate concern as an indicator of recent fecal contamination?

26 Which component of domestic sewage contributes most directly to biochemical oxygen demand?

27 Why can excess nitrogen and phosphorus in treated sewage cause algal blooms in lakes?

28 What is the main purpose of secondary sewage treatment?

29 In an activated-sludge plant, aeration is provided mainly to support microorganisms that:

30 Why is disinfection usually performed after biological sewage treatment rather than before it?

31 A food manufacturer wants to identify the organism responsible for spoilage under refrigerated, oxygen-rich conditions. Which group should be investigated first?

32 A fruit juice develops gas and an alcoholic odor during storage. Which microorganism is the most likely cause?

33 Why are molds more likely than many bacteria to grow on the surface of a relatively dry food?

34 A vacuum-packed food becomes swollen because of microbial gas production. Which organism is a particularly important concern in this low-oxygen environment?

35 Why does drying help preserve food?

36 A refrigerated food has a short shelf life despite having a low temperature. Which explanation is most appropriate?

37 Why is pasteurization not considered a sterilization process?

38 A food product is preserved by adding a high concentration of salt. What is the primary microbial effect?

39 During yogurt production, lactic acid bacteria convert lactose into lactic acid. What is the main result of this process?

40 Which microbial combination is most directly associated with bread production?

41 A groundwater sample contains high counts of heterotrophic bacteria and nitrate, but no detectable E. coli or enteric pathogens. Which interpretation is most defensible?

42 A treated-water sample is negative for total coliforms but positive for Pseudomonas aeruginosa. Which conclusion is most appropriate?

43 Why is detection of thermotolerant coliforms generally more informative about recent fecal contamination than detection of total coliforms in a chlorinated distribution system?

44 A water sample has a high biochemical oxygen demand, a low dissolved-oxygen concentration, and abundant facultative anaerobic bacteria. What process most likely produced this pattern?

45 Which sewage characteristic most directly predicts oxygen depletion in a receiving stream after discharge?

46 Primary sewage treatment removes much suspended material but leaves substantial dissolved organic matter and ammonium. Why is secondary biological treatment still necessary?

47 In an activated-sludge plant, inadequate aeration causes poor floc formation, rising effluent BOD, and loss of nitrification. Which explanation best integrates these observations?

48 A municipality discharges nutrient-rich effluent into a lake. Which treatment modification most directly reduces the risk of downstream eutrophication?

49 Why can land application of inadequately treated sewage contaminate groundwater even when the soil appears to filter suspended particles effectively?

50 A refrigerated vacuum-packed food develops a swollen package and a sulfurous odor without visible mold. Which microbial group should be investigated first?

51 A fruit beverage with low pH and high sugar concentration spoils despite pasteurization that eliminated most vegetative bacteria. Which organism is the most likely cause?

52 In bread dough, yeast produces carbon dioxide but does not normally cause the dough to become strongly acidic. Which metabolic feature explains this outcome?

53 A vacuum-packed cooked meat product is stored at refrigeration temperature and later causes severe intoxication without obvious spoilage. Which combination best explains the hazard?

54 A fermented vegetable becomes soft and develops an unpleasant odor after the salt concentration is reduced substantially. Which microbial shift is most likely?

55 A mold grows on the surface of a low-moisture cereal product and produces a toxic secondary metabolite. Why may the product appear dry while still supporting mold growth?

56 Why does reducing water activity preserve jam more effectively than merely reducing its total water volume by boiling briefly?

57 A heat-sensitive fruit juice is treated by high-pressure processing rather than intense heating. What is the principal preservation advantage?

58 A refrigerated ready-to-eat food remains free of rapidly growing enteric bacteria but is spoiled by a psychrotrophic organism. Which control strategy is most appropriate?

59 In yogurt manufacture, the starter culture first produces acid from lactose, after which the milk proteins coagulate. Which causal relationship is correct?

60 A sourdough culture becomes excessively acidic and produces little gas after repeated refreshments with very little fresh flour. Which explanation is most likely?