Unit 2: Isolation, purification and mass multiplications of entomopathogens - Practice Quiz

1 Which technique is commonly used to obtain separate bacterial colonies from a soil suspension?

2 Why is the surface of a naturally infected insect disinfected before its internal bacteria are isolated?

3 Which material is commonly used as a solid medium for growing bacterial colonies?

4 Heat treatment of a soil suspension can help isolate spore-forming bacteria because their spores are generally:

5 Which method is commonly used to purify a bacterial culture?

6 A pure bacterial culture ideally contains:

7 Which practice helps prevent contamination while transferring a bacterial culture?

8 Which equipment is commonly used for the large-scale multiplication of bacterial biocontrol agents in liquid medium?

9 Which factor is commonly controlled during bacterial mass multiplication?

10 What is the main purpose of adding nutrients to a bacterial fermentation medium?

11 Which method uses susceptible insect larvae to detect entomopathogenic fungi in soil?

12 Which medium is commonly used to isolate and grow entomopathogenic fungi?

13 Which observation most strongly suggests fungal infection in an insect cadaver?

14 Why are antibiotics sometimes added to a fungal isolation medium?

15 Which technique can be used to obtain a pure fungal culture from a mixed culture?

16 What is the purpose of transferring a fungal culture to fresh agar periodically?

17 Which condition is generally suitable for short-term maintenance of fungal cultures?

18 Which substrate is commonly used for the solid-state mass multiplication of entomopathogenic fungi?

19 What is the main infective unit commonly produced during the mass multiplication of many entomopathogenic fungi?

20 Why is adequate aeration important during the mass multiplication of many entomopathogenic fungi?

21 A researcher wants to preferentially isolate spore-forming Bacillus biocontrol agents from soil. Which pretreatment is most appropriate before plating the soil suspension?

22 Which procedure is most suitable for isolating a suspected bacterial pathogen from the internal tissues of a naturally infected insect?

23 A soil suspension produces confluent bacterial growth on every plate. What should be done to obtain countable, well-separated colonies?

24 A primary isolation plate contains colonies with two distinct morphologies. Which method should be used first to obtain a pure bacterial culture?

25 A culture labeled as Bacillus thuringiensis shows both rod-shaped cells and cocci during microscopy. What is the most appropriate response?

26 Which method is most suitable for long-term maintenance of a bacterial biocontrol strain while minimizing genetic change caused by repeated subculturing?

27 A bacterial seed culture is being prepared for inoculating a production fermenter. Which physiological state is generally preferred for rapid establishment in the fermenter?

28 During aerobic bacterial fermentation, dissolved oxygen falls below the required level even though nutrients remain available. Which adjustment should be tried first?

29 A sample from a dilution produces 85 colonies. What was the approximate viable count in the original culture?

30 Two batches of Bacillus thuringiensis have similar viable spore counts, but one causes much lower larval mortality. Which quality test would best detect this difference?

31 A scientist wants to recover insect-pathogenic fungi from soil even when their propagules are present at low density. Which technique is especially useful?

32 A field-collected insect cadaver has fungal growth on its surface. Which procedure best reduces the chance of isolating an external saprophyte instead of the pathogen?

33 When plating an insect tissue suspension for fungal isolation, bacterial colonies rapidly overgrow the plate. Which modification is most appropriate?

34 An entomopathogenic fungal culture contains two fungi that produce similar-looking colonies. Which technique provides the strongest basis for obtaining a genetically uniform isolate?

35 After storage, a fungal biocontrol strain produces many conidia, but most fail to germinate. Which test should be prioritized before using it for mass production?

36 A laboratory observes declining virulence after repeatedly transferring an entomopathogenic fungus on artificial medium. Which maintenance strategy is most appropriate?

37 A production unit requires large quantities of dry aerial conidia of Beauveria bassiana. Which production approach is generally most suitable?

38 In a solid-state fungal production system, the grain substrate becomes waterlogged and develops compact clumps. What is the most likely consequence?

39 A manufacturer wants to produce large quantities of yeast-like blastospores of an entomopathogenic fungus. Which system is most appropriate?

40 Freshly harvested fungal conidia must be dried before formulation. Which practice best preserves their viability?

41 A soil suspension is heat-treated at before plating, and several colonies later produce endospores and parasporal inclusions. Which conclusion is scientifically justified?

42 A bacterium is repeatedly cultured from externally discolored insect cadavers. Which workflow provides the strongest evidence that it is the primary pathogen rather than a postmortem colonizer?

43 An aliquot representing an overall soil dilution of is plated at per plate. The mean count is 48 colonies. Assuming one colony arose from one viable unit, what was the original population?

44 A putative Bacillus thuringiensis plate contains colonies with similar morphology, but microscopy reveals two endospore positions and inconsistent parasporal crystals. What is the most appropriate purification strategy?

45 A Bacillus thuringiensis isolate gradually loses crystal production after frequent transfer on rich agar, although vegetative growth remains normal. Which maintenance plan best minimizes further loss?

46 A non-spore-forming bacterial biocontrol isolate must be maintained for several years with minimal genetic change. Which method is most suitable?

47 A Bacillus thuringiensis fermentation produces high vegetative biomass but poor sporulation and low crystal yield because excess glucose remains late in the batch. Which modification is most appropriate?

48 During scale-up of an aerobic bacterial biocontrol fermentation, oxygen uptake exceeds oxygen transfer and dissolved oxygen approaches zero. Severe foaming prevents a major increase in airflow. What is the best immediate response?

49 A bacterial broth contains . Downstream recovery retains 85% of viable cells, which are blended into of formulation. What is the expected viable count per gram?

50 Two fermentation batches have identical total spore counts, but one has substantially lower insect mortality. Which quality-control combination most directly investigates the discrepancy?

51 A researcher uses only Galleria mellonella larvae to bait entomopathogenic fungi from soil. What is the most important limitation when interpreting the recovered diversity?

52 A field-collected insect cadaver bears mixed external fungal growth. Which procedure most effectively links an isolated fungus to an internal infection rather than incidental surface colonization?

53 Direct soil plating on a medium containing a broad-spectrum fungicide yields no entomopathogenic fungi, whereas insect baiting from the same soil is positive. What is the best interpretation?

54 A sporulating fungal culture contains two morphologically similar genotypes, and a genetically uniform isolate is required. Which purification method is most appropriate?

55 An entomopathogenic fungus loses virulence after many passages on nutrient-rich medium but still sporulates well. Which maintenance system best preserves the original phenotype?

56 A fungal working culture develops a fast-growing, poorly sporulating sector after repeated subculture. What is the most defensible corrective action?

57 In solid-state production of aerial conidia, increasing substrate moisture raises biomass initially but later causes bacterial contamination, heating, and reduced conidiation. Which adjustment best addresses the underlying problem?

58 A product is intended for foliar application in a hot, desiccating environment where propagule persistence is critical. All else being equal, which production target is generally preferable?

59 A solid substrate sample is completely extracted into of suspension containing conidia per milliliter. Extraction recovery is estimated at 80%. What was the estimated production per gram of substrate?

60 A fungal concentrate contains conidia per milliliter, but only 70% germinate. What minimum concentrate volume is required to supply viable conidia?