FAMILY MYXOCOCCACEAE 



1041 



1. Myxococcus fulvus (Cohn emend. 

 Schroeter) Jahn. {Micrococcus fulvus 

 Cohn?, Beitrage z. Biologie d. Pflanzen, 

 1, Heft 3, 1875, 181; Jahn (1924) states 

 that the description of Cohn is too inade- 

 quate to determine whether he was 

 dealing with a true species of the genus 

 Myxococcus. Cohn described the or- 

 ganism from horse dung, as producing 

 conical, rust -red droplets I mm in diam- 

 eter, the cells bound together by an inter- 

 cellular slime, cells large, 1.5 microns in 

 diameter; Micrococcus fulvus Schroeter, 

 Schizomycetes, in Cohn, Kryptogamen- 

 flora V. Schlesien, 3, 1, 1886, 144. Ob- 

 served on horse dung and rabbit dung at 

 various localities. Jahn insists that 

 this organism must be the same as 

 Myxococcus rubescens Thaxter. Myxo- 

 coccus rnbescens Thaxter, Bot. Gaz., 17, 

 1892, 403; Myxococcus ruber Baur, Arch, 

 f. Protistenkunde, 5, 1905, 95; Myxo- 

 coccus pyriformis A. L. Smith, Jour. Bot., 

 39, 1901, 71; Myxococcus javanensis de 

 Kruyff, Cent. f. Bakt, II Abt., 21, 1908, 

 386; Rhodococcus fulvus Winslow and 

 Winslow, Systematic Eelationships of 

 the Coccaceae, 1908, 262; Myxococcus 

 fulvus Jahn, Beitrage zur botanischen 

 Protistologie. I. Die Polj'angiden, Geb. 

 Borntraeger, Leipzig, 1924, 84.) 



Etymology : Latin fulvus, reddish- 

 yellow. 



Swarm stage (pseudo Plasmodium) : 

 Thaxter states that the rod masses are 

 reddish, rods slender, irregularly curved, 

 0.4 by 3 to 7 microns. Bauer followed 

 spore germination in hanging drop. 

 Spores 0.8 to 1.3 microns, without struc- 

 ture, in five hours swollen to 1 to 1.5 

 microns, and no longer as refractive. 

 The membrane is not burst; the cell be- 

 comes egg-shaped, then elongate and 

 cylindric. He regards his Myxococcus 

 ruber as distinct from Thaxter's Myxo- 

 coccus rubescens in part because of differ- 

 ences in spore germination. The cells 

 become motile after doubling or trebling 

 in length. It is a creeping motion in 

 contact with the substrate; the cells do 



not "swim." Rate of motion 5 to 10 

 microns per minute. Rods eventually 

 are 0.5 to 0.7 microns by 4 to 10 microns. 

 Cell division by transverse fission. 

 Spore formation is through shortening 

 and rounding of the cells, the converse 

 of germination. In hanging drop the 

 cells tend to congregate after three days 

 and to transform into spores. Rods 

 sporulate in 3 to 4 hours. The rods con- 

 tinue to congregate, and the spore mass 

 increases, held together by viscous matrix. 

 Vegetative cells are light flesh color. 



Gelatin is quickly liquefied, completelj- 

 in 1 to 2 daj^s, but no fruiting bodies are 

 formed. 



Kofler secured good growth on Ilast- 

 ing's milk agar, and determined digestion 

 of casein. 



Baur could not secure good growth on 

 any agar medium of known composition. 

 With peptone, sugars, etc., some growth 

 but not normal when peptone present. 

 He carried one strain 3J months on pep- 

 tone sugar agar. Good growth on dung 

 agar. Addition of peptone to dung agar 

 not significant in effect, the addition of 

 glucose altered the form of the fruiting 

 bodies. 



De Kruyff secured best results with a 

 dung extract agar to which was added 

 ammonium nitrate and potassium phos- 

 phate. 



Fruiting bodies : Spherical or elongate 

 pear-shape, constricted below, often 

 with definite slimy stalk, flesh red to 

 brownish-red, when dry rust -red to brown, 

 about 300 microns in diameter. Spores 

 1 to 1.2 microns. Jahn (1924, loc. cit.) 

 notes two varieties. 



var. albus. (Latin albus, white). 

 Constantly white, even when 

 transferred. Fruiting bodies some- 

 what smaller than the type, 

 var. miniatus. (Latin miniatus, 

 painted with red lead or cinnabar.) 

 Color cinnabar-red, fruiting bodies 

 somewhat larger. 

 The form described by de Kruyff had 

 spores 1.6 microns in diameter. 



