46 BIOLOGY OF BACTERIA 



31. What is meant when certain bacteria are said to reduce nitrates to nitrites? 



32. What is a chromogenic bacterium? 



33. What are some of the conditions necessary to the formation of bacterial 

 pigments? 



34. What are some of the conditions favorable to the formation of bacterial 

 pigments? 



35. Enumerate several species of chromogenic bacteria and describe their 

 pigments. 



36. Where are phosphorescent bacteria found ? What is meant by this term ? 



37. What different enzymes are furnished by various pathogenic bacteria? 



38. Explain the action and name the fermentative products of the following 

 enzymes : 



(a) Diastase. (d) Urase. 



(6) Invertase. (e) Lipase. 



(c) Rennet. (/) Pepsin or trypsin. 



39. What is meant by the statement that a bacterium belongs to the (a) 

 liquefying; (6) non-liquefying type? 



40. What does the anthrax bacillus form when growing in a medium contain- 

 ing sugar ? 



41. What does the bacillus of malignant edema form under similar but 

 anaerobic conditions? 



42. What does the Bacillus lactis aerogenes form from sugar? 



43. How does bacterial growth affect the reaction of the culture soil? 



44. What occurs in slightly alkaline milk when the colon bacillus develops 

 in it? 



45. What is meant by symbiotic pathogenic bacteria? 



46. What is meant by bacterial antagonism ? 



47. Name some symbiotic and some antagonistic pathogenic bacteria. 



48. What generally is the effect of direct sunlight upon pathogenic bacteria? 



49. What is the effect of an electric current passing through a fluid culture 

 medium containing bacteria? Upon what does the effect depend? 



50. What is the meaning of the term antiseptics? Name some of those most 

 commonly employed. 



51. What is the comparative effect of dry and moist heat upon bacteria and 

 their spores? 



52. What is the meaning of the terms: (a) sterilization; (6) aseptic? 



53. How can blood be obtained from an animal in an aseptic manner? 



54. What is the meaning of the term bacterial contamination ? 



