HETEROTROPHIC BACTERIA REQUIRING COMBINED NITROGEN 157 



soils may be entirely free from thermophilic organisms; 42 the geographic 

 condition has no influence. 43 



Globig 32 isolated a number of thermophilic bacteria from the soil 

 and believed that, because most of them were isolated from the surface 

 layers, the rays of the sun supply the heat necessary to obtain the high 

 temperatures. Rabinowitsch 34 isolated eight species of thermophilic 

 bacteria from soil and feces, var} r ing in morphology (rod shaped to 

 comma shaped), size of spores, color of colony on agar and potato. A 

 number of other bacteria were isolated 35 which had an optimum at 

 60° to 65°C. and were killed by heating at 100°C. for 8 to 20 hours. 

 A variety of B. coli and a spore-bearing organism, Bac. calfactor, as well 

 as several fungi and actinomyces, were found capable of growing at high 

 temperatures and taking an active part in the decomposition of hay. 40 

 The size of Bac. caljacior changes with temperature at which it is grown 

 (on hay infusion agar at 70°C. it is 5 by 0.4/z; at 56°C. — 5 by 0.7^; at 

 30°C— 3 by 0.8/x). The rods occur singly, not in chains, and are motile 

 at favorable temperatures (above 30°). The spores are 1.5 by 0.8/x. 

 Spore germination takes place in 60 minutes at 60°C. ; in 85 minutes, 

 2 cells are already formed. This rapid multiplication accounts for the 

 fact that at 50°C, turbidity is definite in liquid decoctions within six 

 hours and an abundant growth is produced on agar. 



de Kruyff 44 isolated from the soil ten species of rod shaped, thermo- 

 philic bacteria, most of them being long rods, forming oval to round 

 spores; most of them produce proteolytic enzymes and do not grow on 

 potato. He suggested that with a rise in temperature in tropical soil 

 they take the place of the ordinary bacteria. It has been established 

 that there occur in soils thermophilic nitrogen-fixing bacteria, 45 ther- 

 mophilic cellulose decomposing bacteria 46-48 and thermophilic denitri- 



42 Migula, W. tiber die Tatigkeit der Bakterien im Waldboden. Forst- 

 wissensch/Zentrbl. 57 (Neue Folge 35): 161-169. 1913. 



43 Mischustin, E. Untersuchungen xiber die Temperaturbedingungen fur 

 bakterielle Prozesse im Boden in Verbindung mit der Anpassungsfahigkeit der 

 Bakterien an das Klima. Centrbl. Bakt. II, 68: 328-344. 1926. 



44 de Kruyff, E. Les bacteries thermophiles dans les Tropiques. Centrbl. 

 Bakt. II, 26: 65-74. 1910. 



46 Pringsheim, 1911 (p. 121). 



46 Pringsheim, 1913 (p. 202). 



47 Kroulik, A. tiber thermophile Zellulosevergarer. Centrbl. Bakt. II, 36: 

 339-346. 1912. 



45 Viljoen, Fred and Peterson, 1926 (p. 202). 



