192 PRINCIPLES OF SOIL MICROBIOLOGY 



Omeliansky found that the mixture of gases contained hydrogen or 

 methane, these two gases being produced by two different organisms. 

 When the inoculum was added without preliminary heating, methane 

 formation took place; when the inoculum was heated for 15 minutes at 

 75°, conditions favored the development of the bacteria which produced 

 hydrogen in the decomposition of cellulose. The spore of the methane- 

 forming organism was found to germinate earlier than that of the hy- 

 drogen form. When the culture was transferred, the former organism 

 predominated and the latter could be finally entirely eliminated. 

 By heating the inoculum or a young culture, the vegetative cells pro- 

 duced from the spores of the methane form, which had already germi- 

 nated, were killed, while the ungerminated spores of the hydrogen form 

 survived and proceeded to develop. If this process of heating the cul- 

 ture at an early stage of development was repeated several times, the 

 hydrogen form could be obtained free from the methane form. 



PLATE XI 



Cellulose and Pectin-decomposing Bacteria 



64. (x), Bac. cellulosae hydrogenicus syn Bac. fossicularum L & N, and (y), 

 Bac. cellulosae methanicus syn Bac. methanigenes L & N: a, young cells; b, spore 

 formation; c, ripe spores, X 660 (from Omeliansky). 



65. Bac. cellulosae dissolvens, showing bacteria attached to the cellulose fiber, 

 by their non-sporulating extremities (from Khouvine). 



66. Holes in paper produced by Spirochaeta cytophaga, grown in Petri dish 

 culture upon NaN0 3 — mineral salt agar with filter paper superimposed, natural 

 size (from Hutchinson and Clayton). 



67. Spirochaeta cytophaga, young culture on filter paper placed in tube; typical 

 incurvation of thread forms (from Hutchinson and Clayton). 



68. Sp. cytophaga, formation of pre-sporoid stage with double granules (from 

 Hutchinson and Clayton). 



69. Bad. fimi, 15-day old colonies on cellulose agar plate, at 30°C. (from 

 McBeth and Scales). 



70. Bact. fimi, vegetative cells from 24-hour culture on nutrient agar, stained 

 with carbol-fuchsin, X 660 (from McBeth and Scales). 



71. Bac. cytaseus, 15-day old colonies on cellulose agar plate, at 30°C. (from 

 McBeth and Scales). 



72. Bac. cytaseus, nine day old culture at 30°C, showing spore formation; 

 aqueous fuchsin stain, X 660 (from McBeth and Scales). 



73. Clostridium thermocellum, a thermophilic cellulose decomposing bacillus. 

 A 48 starch-lagar culture at 65°C. stained with carbol fuchsin for 5 minutes, at 

 100°C, showing free spores, sporangia and vegetative rods (from Viljoen, Fred 

 and Peterson). 



74. Granulobacter pectinovorum (after Beijerinck). 



