tically no spreading in semisolid agar and only wiggling and spin- 

 ning motion in liquid media. 



Next to the curly the most common variant is the coiled type. 

 The flagella of one genus of bacteria, Scrmtia, are mainly coiled. 

 The coiled shape may be the flattened appearance of a helix with 

 a very large amplitude and short wavelength. This shape is fairly 

 frequent in many genera of both peritrichous and polar bacteria 

 but it is rare to find a culture which shows only coiled flagella. 

 Aside from Serrafio, cultures showing only coiled flagella have been 

 found in Aeromonos, Listeria (true mutant), Escherichia, and 

 Erwinia. Locomotor efBciency of coiled flagella is fair but less 

 than that of normal flagella. 



Other shape variations less frequent than those mentioned are 

 straight, small amplitude, and undulant. Straight flagella are oc- 

 casionally seen among the normal flagella of many bacteria. Pure 

 variants or mutants with straight flagella are rare. Stable variants 

 with straight flagella have been isolated from several cultures of 

 Listeria. One strain of Arthrobacter studied had mainly straight 

 flagella. Organisms with straight flagella are either nonmotile or 

 show only a nonprogressive spin or wiggle. Both types have been 

 observed in Listeria. 



Organisms with small amplitude flagella have been observed 

 in Listeria, Sarcina, Rhizobium, and occasionally in other genera. 

 Pure variants with this type of flagella have been isolated from 

 Listeria strains. The motility of these variants was poor and prac- 

 tically nonprogressive, like organisms with straight flagella. 



The undulant type of flagella was observed on one strain of 

 Thiobacillus thiopariis, on several strains of halophilic Pseiido- 

 motias species, and on several strains of Aeromonus. This is the 

 type of flagella found on algae, such as Chlaniydotnonas, on pro- 

 tozoa, and apparently on flagellated plant gametes. With the single 

 exception of a peritrichous organism seen in water all undulant 

 flagella seen have been polar. 



Variation of Flagellar Arrangement 



Variation of flagellar arrangement is relatively rare but has 

 been observed in several genera. The variation is always from 

 polar flagellation or subpolar flagellation to peritrichous flagella- 



15 



