GENERAL SYSTEMATIC BACTERIOLOGY 393 



Myxobacteriaceae. The name of a family proposed by Thaxter 

 (1892, p. 394) to include the so-called Myxobacteria. The name comes 

 from the genus (now abandoned) Myxobader Thaxter. 



The family diagnosis as given by E. F. Smith is as follows (1905, 

 p. 164): 



Motile, rod-like organisms, multiplying by fission secreting a gelatinous base, 

 and forming pseudoplasmodium-like aggregations before passing into a more or 

 less highly developed cyst-producing, resting state in which the rods may become 

 encysted in groups without modification, or may be converted into spore-masses. 

 The vegetative rods, which vary little in size and form in the different genera and 

 species, are typically elongate, sometimes reaching 15/Lt in length. Cell division 

 follows an elongation and nearly medium constriction of the rods which, except 

 at the moment of division, are always separate, never united in chains. A slow, 

 sliding locomotion and a Beggiatoa-like, bending motion is characteristic of the 

 active rods. Organs of motion have not been detected. In all species, with 

 one exception, the rods, when seen in masses, are more or less distinctly reddish, 

 A distinct, firm, hyaline gelatinous base is secreted by the colony as it extends 

 itself, over which the individuals may move or in which they become imbedded. 



The vegetative period, in artificial cultures, usually lasts about a week, or even 

 two weeks, but in nature the production of cysts must be more rapid. Common in 

 moist situations on dung, decaying wood, fungi, lichens, etc. According to 

 Bauer they grow best at 30°C. 



In forms like Myxococcus in which the rods are somewhat scattered, the first 

 preparation for spore production as seen under the microscope consists in 

 the appearance of groups of rods moving with a circular tendency, in which the 

 more central individuals soon become converted into the spores. The formation 

 of a cystophore, when it occurs, results from the basal constriction of a papillate 

 mass of rods which projects from the surface of the colony. In the encysted 

 condition there are two classes — one in which the individuals thus encysted show 

 little or no modification from the rod-like vegetative state, the other in 

 which they are converted into definite spores. They, however, seem to run into 

 one another. 



This family name is also used by Clements (1909, p. 8) and by 

 Benecke (1912). 



Buchanan (1918, p. 541) included this as the single family of the 

 order Myxobader tales, with characters those of the order, q.v. Three 

 genera were included: Chondromyces, Polyangium and Myxococcus. 

 Bergey et al. (1923, p. 412) follow Buchanan. 



Myxobacteriales. An ordinal name proposed by Buchanan (1917,. 

 p. 163). The description (1918, p. 541) follows. 



Motile, rod-like organisms, multiplying by fission, secreting a gelatinous base, 

 and forming a pseudoplasmodium-like aggregation before passing into a more or 

 less highly developed cyst-producing, resting state in which the rods may become 

 encysted in groups without modification, or may be converted into spore masses. 



There is one family only, the Myxobacteriaceae. 



