AUTOTROPHIC BACTERIA 99 



means of a single polar flagellum. The gelatin colonies were yellow, 

 smooth, rarely greenish; the gelatin was not liquefied. Yellow to 

 greenish growth on agar. 



Kaserer suggested that both the methane and hydrogen oxidation 

 phenomena are of great importance in the soil, due to the fact that 

 these substances, which are produced in the subsoil by anaerobic proc- 

 esses, are thus oxidized and made available to the soil. 



Kaserer's medium consisted of: 



K2HPO4 0.5gram NaHC0 3 0.5 gram 



MgS0 4 0.2 gram FeCl 3 Trace 



NH4CI 1.0 gram Water 1000 cc. 



The organism growing on this medium developed poorly under auto- 

 trophic conditions, the oxidation of hydrogen becoming prominent 

 in the presence of small amounts of soluble organic matter. 108 A non- 

 motile bacterium, 1.4 by 0.5/x in size, was isolated, different from the H 

 ■pantotropha of Kaserer. The greatest amount of hydrogen was oxidized 

 in the presence of 0.01 to 0.03 per cent peptone, nutrose or sodium 

 asparaginate. In association with certain bacteria, the organism was 

 much more active. 



Niklewski used a medium containing: 



NH4CI l.Ogram NaCl 0.2 gram 



KH 2 P0 4 l.Ogram FeCl 3 0.0001 gram 



MgS0 4 -7H 2 0.2 gram Agar 15.0 grams 



NaHCOj l.Ogram Water 1000 cc. 



The cultures were placed in a bell-jar, through which purified hydrogen was 

 passed, at 38° to 35°C. The cultures developed in 3 to 4 days. Two organisms 

 were isolated: 



Hydrogenomonas vilrea formed a pellicle on the surface of the liquid medium. 

 Small yellow subsurface colonies were formed on the agar. On the surface the 

 colonies were transparent, folded. The cells are 2/i long. Obligate autotrophic. 

 No motility observed. 



Hydrogenomonas flava formed shining yellow colonies on the surface of the 



agar, not spreading as rapidly as the H. vitrea, surface smooth, edge entire; 



microscopically, the cells were found to be somewhat smaller (1.5/* long). No 



pellicle formation on liquid media. Obligate autotrophic. No motility observed. 



By further study, Niklewski 109 isolated an organism (H. agilis) which can oxi- 



108 Harrison, W. H., and Aiyer, P. A. S. The gases of swamp rice soils. III. 

 A hydrogen-oxidizing bacterium from these soils. Mem. Dept. Agr. India, Chem. 

 Ser. 135-148. 1916. 



109 Niklewski, B. Uber die Wasserstoffaktivierung durch Bakterien unter 

 besonderer Beriicksichtigung der neuen Gattung Hydrogenomonas agilis. Kos- 

 mos, Lemberg. 1923. (Centrbl. Bakt. II, 40: 430-433. 1914.) 



