1010 MANUAL OF DETERMINATIVE BACTERIOLOGY 



types of soils. Polyangium cellulosum var. ferrugineum Mishustin and Polyangium 

 celhilo swn var . fuscum M'lshustin {loc. cit.) were observed to be common in the black 

 soils of Eastern European Russia, while a similar variety of the same species was 

 reported only from podzol soils. Species of the families Polyangiaceae, Sorangiaceae 

 and to a lesser degree Archangiaceae appear to predominate in Russian and European 

 soils, while the soils of Central and Western United States seem to be more suitable 

 for the growth of the Myxococcaceae. Soils of mountainous regions are said to contain 

 fewer numbers of myxobacteria than those of lowland areas. 



The distribution of myxobacteria in the soil seems to show a relationship to the 

 hydrogen ion concentration. Some species are found only in neutral or alkaline soils 

 (pH 7.0 to 8.0), others only in acid soils (pH 3.6 to 6.4). Some species show a wide 

 tolerance (pH 3.6 to 8.0). 



Relationships of the Myxobacteria. The resemblance of the pseudoplasmodium 

 of the myxobacteria to the Plasmodium of the slime molds is as noted above probably 

 to be regarded as without significance, as is also the superficial resemblances of the 

 fruiting bodies of the two groups. Jahn (1924, loc. cit.) dismisses the relationship to 

 the Thiobacteriales suggested by Thaxter as improbable. Thaxter believed the pos 

 session of the red color might show presence of bacteriopurpurin; but Jahn found a 

 carotin reaction which argues against this idea. Jahn insists upon a close relation- 

 ship to the blue-green algae, particularly because of the mobility of the cells and the 

 creeping motion. He does not believe all Schizophylae that do not belong to the 

 Cyanophyceae (blue-green algae) should be grouped as bacteria. He believes the 

 myxobacteria to be more closely related to the blue-green algae than to the true bac- 

 teria, and creates the class Polyangidae to be coordinate with the class Schizomycetes . 

 In this he ignores the equal evidence of close relationship of the sulfur bacteria to 

 the Cyanophyceae. His argument would lead to the recognition of all the orders of 

 bacteria recognized in this Manual as classes. The wisdom of this is not apparent. 

 The Myxobacteriales may be regarded as a well -differentiated order of the Schizo- 

 mycetes showing some resemblance to the true bacteria on the one hand and the Myxo- 

 phyceae (Cyanophyceae) and Thiobacteriales on the other. 



Families of the Myxobacteriales. The division of the order Myxobacteriales into 

 families has been based, in all classifications proposed, upon morphology. The final 

 demonstration by Stanier (Jour. Bact., 40, 1940, 636) of the close relationship between 

 species of the genus Cytophaga and the myxobacteria led him to propose the recognition 

 of a new family, Cytophagaceae. 



The principal character differentiating this family from the four previously recog- 

 nized is the absence of differentiated fruiting bodies. The resting cells are rod-shaped 

 in the genus (Cytophaga). In another genus recognized by Stanier (Sporocytophaga) 

 the resting cells are spherical. This brings the taxonomist face to face with the 

 problem of deciding whether the presence of fruiting bodies or the spherical shape 

 of the spores should be the primary basis of differentiation. The formation of 

 spherical spores is believed to be of sufficient significance to require the inclusion of 

 all organisms producing such in the ia,uii\yMyxococcaceae. Sporocytophaga, although 

 it produces no fruiting body, is therefore placed in this family, while those forms 

 which produce neither spherical spores nor fruiting bodies (genus Cytophaga) are 

 placed in the new family Cytophagaceae. 



Krzemieniewska's (Acta Soc. Bot. Pol., 7, 1930, 507 and Arch. Microbiol., 4, 1933, 

 394) conclusion that two distinct cell shapes appear in the mj'xobacteria (short, thick 

 rods with ends almost truncate, and long, slender rods almost spindle-shaped in some 

 cases with pointed tips) is supported by Stanier (Bact. Rev., 6, 1942, 143) as also the 



