FAMILY NITROBACTERIACEAE 



79 



Key to the species of genus Thiobacillus. 



I. Aerobic. 



A. Strictly autotrophic. 



1. Optimum reaction for growth close to neutrality. 



1. Thiobacillus thioparus. 



2. Optimum reaction for growth pH 2.0 to 3.5. 



2. Thiobacillus thiooxidans . 



B. Facultative autotrophic. 



3. Thiobacillus novellus. 



4. Thiobacillus coproliticus . 



II. Anaerobic in presence of nitrate. 



5. Thiobacillus denitrificans. 



1. Thiobacillus thioparus Beijerinck. 

 (Cent. f. Bakt., II Abt., 11, 1904, 593; 

 Nathanson, Mitt. Zool. Station Neapel, 

 15, 1902, 655 ; Sulfomonas thioparus Orla- 

 Jensen, Cent. f. Bakt., II Abt., 22, 1909, 

 326). From Greek theion, sulfur and 

 paro, to make. 



Thin, short rods, 0.5 by 1 to 3.0 mi- 

 crons. Motile (non-motile culture re- 

 ported. See Starkey, Soil Sci., 39, 1935, 

 197.) Gram-negative. 



Thiosulfate medium (liquid) : Pellicle 

 consisting of cells and free sulfur. 



Thiosulfate agar: Colonies small, cir- 

 cular, whitish yellow due to precipitated 

 sulfur. 



Optimum reaction : Close to neutrality. 



Strictly autotrophic. Derives its en- 

 ergy by the oxidation of thiosulfate to 

 sulfate and sulfur ; also oxidizes sulfur to 

 sulfate. 



Aerobic. 



Source : Sea water, river water, mud, 

 sewage, and soil. 



Habitat : Presumably widely distrib- 

 uted. 



2. Thiobacillus thiooxidans Waksman 

 and Joffe. (Jour. Bact., 7, 1922, 239; 

 Sulfomonas thiooxidans Waksman, Jour. 

 Bact., 7, 1922, 616; Thiobacterium thiooxy- 

 dans Lehmann and Neumann, Bakt. Diag., 

 7 Aufl., 2, 1927, 517.) From Greek 

 theion, sulfur and M.L. to oxidize. 



Short rods: 0.5 by 1.0 micron with 

 rounded ends. Occur singly, in pairs, 

 or in chains . Motile by means of a single 



polar flagellum. Gram-negative (Star- 

 key, Soil Sci., 55, 1935,210). 



Thiosulfate agar: Scant growth. 

 Nearly transparent colonies. 



Sulfur medium (liquid) : Uniform tur- 

 bidity. No sediment or surface growth. 

 Medium becomes very acid (below pH 

 1.0). 



Thiosulfate medium (liquid) : Uniform 

 turbidity. Medium becomes acid and 

 sulfur is precipitated. 



Nitrogen sources: Utilizes ammonia 

 nitrogen but not nitrate nitrogen which 

 is toxic. Asparagin, urea and peptone 

 not utilized. 



Temperature relations : Optimum 28° 

 to 30°C. Slow growth at 18° and 37°C. 

 Death occurs at 55° to 60°C. 



Optimum reaction: pH 2.0-3.5. 

 (Limiting reactions, pH 6.0 to less than 

 pH 0.5.) 



Strictly autotrophic, deriving its 

 energy from the oxidation of elementary 

 sulfur and thiosulfate, oxidizing these to 

 sulfuric acid. It utilizes the CO2 of the 

 atmosphere as a source of carbon. 



Strictly aerobic. 



Distinctive characters : This species 

 produces more acid, from oxidation of 

 sulfur, and continues to live in a more 

 acid medium, than any other living or- 

 ganism yet reported, the hydrogen-ion 

 concentration of the medium increasing to 

 a pH 0.6 and less. 



Source : Isolated from composts of soil, 

 sulfur, and rock phosphate and soils con- 

 taining incompletely oxidized sulfur 

 compounds. 



Habitat: Soil. 



