1. Technical Problems Related to Motility and 

 Flagellation 



The Bacterial Culture 



The synthesis of flagella and their activity does not always 

 correlate with the other physiological activities of the bacteria. 

 The environment which is best for growth and metabolism is not 

 always best for flagellation and motility. Substances which have 

 very minor effects on somatic growth and metabolism may com- 

 pletely inhibit flagellation or flagellar activity. 



As a general rule flagellation is best in cultures incubated at 

 relatively low temperatures such as 20° C. With some mesophilic 

 bacteria little difference may be found in the flagellation observed 

 at 20 and 37° C. With some genera, such as Listeria, the flagella- 

 tion at 20° C. is good while that at 37° C. is very poor, and at 

 38° C. flagella are absent. In rare instances flagellation is better 

 at higher temperatures than at lower temperatures. The only ex- 

 ample the author can cite from personal experience is a culture of 

 Salmonella in which both the flagellation and motility were dis- 

 tinctly better in cultures incubated at 37° C. as compared to 20° C. 

 In many instances the apparently adverse effect of the higher tem- 

 peratures of incubation is not due to the temperature as such, but 

 rather to the growth phase in which the bacteria are examined. 

 Overnight incubation at 37° C. of bacteria such as those of the 

 enteric group, finds the bacteria long past the logarithmic phase 

 and well into the death phase, while after the same length of 

 incubation at 20° C. the bacteria are in a much more active state. 

 After growth has ceased, the flagella may deteriorate more rapidly 

 than the soma. 



The optimum length of incubation for best flagellation seems 

 directly related to the growth rate. In general it appears that the 

 best flagellation is observed during the logarithmic and maximum 

 stationary phases of growth. In one genus of bacteria, Aeromoruis, 

 the nature of the flagellation may change during the growth cycle. 

 Strains of this genus may show numerous lateral flagella in young 



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