ORDER MYXOBACTERIALES 1007 



failed to prove it by plasmolytic agents. Jahn states that tinctorial and chemical 

 methods failed to definitely show the presence of a membrane, but that the elasticity 

 of the cells show this clearly. The cells are flexible, not rigid as are ordinary bac- 

 teria. Beebe (Jour. Bact., 4^, 1941, 214) reported the presence of a cell membrane in 

 Myxococcus xanthus, often made visible with proper staining procedures. The cells 

 frequentlj" show one or more refractive granules. Thaxter also noted nucleus-like 

 granules in the spores of Myxococcus, while Bauer (Arch. f. Protistenk., 5, 1905, 92) 

 reported that during germination of the spores of Myxococcus a refractile granule is 

 found at each end of the cell. Badian (Acta Soc. Bot. Pol., 7, 1930, 55) stated that 

 the cell of Myxococcus vircscens lacks a true nucleus, but that there is present a baso- 

 philic structure probably nuclear in nature. It is dumb-bell-shaped and divides 

 longitudinally in mitosis. In spore formation an autogamy occurs followed by what 

 appears to be a reduction division. All chromatin material was Gram-negative except 

 during reduction; it may be stained by hematoxylin. Beebe noted a condensed 

 mass of nuclear material in the vegetative cells of Myxococcus xanthus that divided 

 by constriction prior to each cell fission. Nuclear division is considered to be non- 

 random amitosis. Cell division is by means of constriction at a point near the center 

 and is always complete. The nucleus is stained by gentian violet and by iron-hema- 

 toxylin and gives a faintlj' positive Feulgen reaction. What appears to be an autog- 

 amous fusion of chromosomes takes place during sporulation, followed by a nuclear 

 division during germination of the spores. The spores germinate by a process anala- 

 gous to budding. Vahle (Cent. f. Bakt., II Abt., 25, 1909, 178) found fat globules 

 and occasional small volutin granules in 3 to 4 day old cultures. Glycogen was not 

 found. 



In masses the vegetative rods may be somewhat reddish in color. Thaxter suggested 

 the possibilitj- that the color might be bacteriopurpurin. Treated with concentrated 

 sulfuric acid the pigment gives a blue reaction, hence Jahn (1924, loc. cit.) concludes 

 it to be carotin. 



Motility of the cells. Baur {loc. cit.) states that cells have a power of forward 

 movement at a rate of about 10 microns per minute. Xo flagella are present. The 

 cells do not "swim." They may bend and are unlike most true bacteria in this 

 respect, though Dobell (Quart. Jour, of Microscop. Science, 56, 1911, 395 and Arch, 

 f. Protistenkunde, S6, 1912, 117) describes such flexibility for the giant bacteria (see 

 Bacillus fiexilis). This is characteristic also of Bcggialoa, Oscillatoria and 

 Spirochaeta. 



The cells en masse move in a "front," advancing and leaving behind a slime. The 

 cells in general tend to lie on rather than in the slime. The exact mechanism of 

 motion has proved puzzling. Jahn believes the motion to be related to that of forms 

 like Oscillatoria, and to be due to excretion of slime from the cell, probably an asym- 

 metrical excretion which pushes the cell along. 



The colony. This has been variously termed a swarm, pseudoplasmodium, Plas- 

 modium and reproductive communalism. It bears a faintly superficial resemblance 

 to the Plasmodium of certain of the slime molds {Myxomycetes) but differs in that the 

 true Plasmodium is composed of the fused bodies of large numbers of amoeboid cells. 

 The myxobacterial colony is an aggregation of individual rod-shaped, bacterial cells 

 that are not amoeVjoid. The slime produced by the cells is not protoplasmic, and the 

 colony is not motile but increases in size as the cells move away from the center. 

 Larger numbers of cells are to be found at the margins than on the central portions of 

 the colony ; in consequence , fruiting bodies tend to be found in concentric rings on 

 the colony. The cells lie on the surface of the slime which they secrete, not in it. 



