ORDER MYXOBACTERIALES 1005 



ORDER IV. MYXOBACTERIALES JAHN.* 



(Kryptogamenflora der Mark Brandenburg, V, Pilze 1, Lief. 2, 1911, 201.) 



Synonymy: M yxobacteriaeae Thaxter, Bot. Gaz., 17, 1892, 389; Myxobactrales 

 Clements, The genera of fungi. Minneapolis, 1909, 8; Synbacteries Pinoy, Compt. 

 rend. Acad. Sci., Paris, 157, 1913, 77 ; Myzobacterieae Heller, Jour. Bact., 6, 1921, 521 ; 

 Polyangidae Jahn, Beitrage zur botanischen Protistologie, I, Die Polyangiden, Geb. 

 Borntraeger, Leipzig, 1924; Myxobacteriae Stanier and van Niel, Jour. Bact., ^2, 

 1941, 437. 



The name Myxobacteriaceae, although having the form of a family designation, 

 was proposed by Thaxter {loc. cit.) in an article bearing the title "On the Myxobac- 

 teriaceae, a new order of Schizomycetes ." Apparently the first ordinal name was 

 that given by Clements {loc. cit.), but does not follow the spelling fixed by the prece- 

 dent of Thaxter. The revised spelling was given by Jahn as Myxobacteriales . Pinoy 

 {loc. cit.) suggested Synbacteries. The name Myxobacterieae was proposed by Heller 

 {loc. cit.) as a class designation, Bacteria being regarded as the designation of a phylum. 

 Polyangidae is likewise a class designation, Jahn (1924, loc. cit.) concluding this group 

 should be coordinate in rank with the Schizomycetes. Buchanan (Jour. Bact., S, 

 1918, 541) proposed the name Myxobacteriales, not knowing of the previous use of 

 the term. He has therefore at times been incorrectly designated as the author of 

 the name. 



It may be argued that a more appropriate ordinal designation might be Polyangiales, 

 inasmuch as the generic name Myxobacter proposed by Thaxter was soon found to be 

 a synonym of Polyangium Link. However, there would seem to be justification of 

 the retention of a name based upon an "ancient generic name" in Rule 21 of the Brus- 

 sels Code. 



The group is herein regarded as an order, though Jahn, and Stanier and van Niel 

 agree in regarding it as a class. 



Common or trivial names. The slime bacteria, my.xobacteria or polyangids. 



Brief characterization of the order. The relatively long, slender, flexible, non- 

 fiagellate vegetative cells produce a thin, spreading colony (pseudoplasmodium, 

 swarm). The cells are often arranged in groups of 2 or 3 to a dozen or more, their 

 long axes parallel. The group moves as a unit, by means of a crawling or creeping 

 motion, awaj^ from the center of the colony. The moving cells pave the substrate 

 with a thin layer of slime on which they rest. 



During sporulation (which occurs in all forms except members of the genus Cylo- 

 phaga) the cells are much shortened, in some cases becoming spherical or coccoid, 

 thick-walled and highly refractile. Fruiting bodies are formed by the species of all 

 families except the Cytophagaceae and the genus Sporocytophaga of the family Myxo- 

 coccaceae. The fruiting bodies may consist of aggregations of cysts in which the 

 spores (resting cells) are inclosed, or of masses of mucilaginous slime surrounding 

 large numbers of shortened, rod-shaped, or coccoid spores. Fruiting bodies may be 

 sessile or stalked. They are usually pigmented a bright shade of orange, yellow, 

 red or brown, though colorless fruiting bodies, as well as black, have been described. 



* The section covering the order Myxobacteriales was first developed in its present 

 form by Professor R. E. Buchanan, Iowa State College, Ames, Iowa, for the fourth 

 edition of the Manual issued in 1934. It was revised by Professor Buchanan for the 

 fifth edition in 1939. The present review has been carried out by Dr. J. M. Beebe 

 and Professor R. E. Buchanan who had had material assistance from Dr. R. Y. Stanier, 

 April, 1943. 



