106 Microbes and You 



The following terminology has been commonlv accepted to describe 

 arrangement of flagella: 



Monotrichic a single flagellum at one end. 



Lophotrichic a tuft of two or more flagella at one end. 



Amphitrichic one or more flagella at each end. 



Peritrichic flagella around the entire perimeter. 



When flagella are lacking, the organism is said to be atrichic. 

 It has been suggested by some workers that amphitrichic flagella- 

 tion as such does not exist. What is being viewed is two mono- 

 trichic or two lophotrichic organisms about to divide but not as 

 yet completely separated into individual organisms. Others classify 

 motile bacteria into but two categories: Those having only lateral 

 flagella, and those possessing only terminal organs of locomotion. 

 Any finer breakdown, to these scientists, seems unjustified. 



Movement of flagella is not mere thrashing about. An apparent 

 rotating motion propels them through fluids. Periodic contractions 

 run around the flagella from one end to another, giving the 

 appearance of a rotary motion. These rhythmic contractions are 

 capable of forcing organisms through liquids at a rate exceeding 

 100 microns per second, although 25 to 30 microns per second is 

 more common. The cholera organism has sped through a measured 

 course at a registered speed of 8 inches per hour, and this speed 

 can apparently be maintained for considerable time. The angle 

 formed by the flagella with the cell body determines the direction 

 of movement. 



These protoplasmic threads, as they are referred to by some 

 investigators, have a constant arrangement for each species on 

 which flagella are found, and this can usually be relied upon 

 in the identification of organisms. We can slow down the speed 

 of organisms by growing them in a semi-solid medium which is 

 more viscous than nutrient broth. 



STAINING OF MICROBES 



Bacteria stain well with basic (in the sense of pH) dyes be- 

 cause of the dye affinity of the nucleic acids contained in the 



