FAMILY III. THIOBACTERIACEAE 83 



Molisch, Cent. f. Bakt., II Abt., 33, 1912, of the cell). Both ends are more or less filled 

 55; Vislouch, Jour, de Microbiologie (Riis- ^vith large volutin (metachromatic) gran- 



sian),/, 1914,50.) 



bi.punc.ta'ta. L. bis twice; L. noun 

 punctum a point, spot; M.L. adj. bipunc- 

 tatus two-spotted 



ules. Several minute granules of sulfur are 

 present in the clear center and sometimes at 

 the ends. Old cells possess one flagellum at 



Small, slightly bent sulfur spirilla, mark- each end; young cells have a flagellum at one 

 edly pointed at the ends; 6.6 to 14 microns end. 

 long, 1.7 to 2.4 microns wide (in the center Habitat: Sea and salt waters. 



Genus V. Thiobacillus Beijerinck, 1904* 



(Beijerinck, Cent. f. Bakt., II Abt., 11, 1904, 593; not Thiobacillus Ellis, Sulphur Bacteria, 

 London, 1932, 130; Sulfomonas Orla-Jensen, Cent. f. Bakt., II Abt., 22, 1909, 314.) 



Thi.o.ba.cil'lus. Gr. noun^ium sulfur; L. noun bacillus a small rod; M.L. mas.n. Thio- 

 bacillus a sulfur rodlet. 



Small, Gram-negative, rod-shaped cells. Non-motile or motile, usually by means of a 

 single polar flagellum. Energy derived from the oxidation of incompletely oxidized sulfur 

 compounds, principally from elemental sulfur and thiosulfate but in some cases also from 

 sulfide, sulfite and polythionates. The principal product of oxidation is sulfate, but sulfur 

 is sometimes formed. Grow under acid or alkaline conditions and derive carbon from carbon 

 dioxide or from bicarbonates in solution; some are obligate and some facultatively auto- 

 trophic. Some species are anaerobic in the presence of nitrate. Found in soil, mine waste- 

 waters, sewage, effluents and related sources. 



The type species of this genus is strictly autotrophic as are the majority of the species in 

 the genus. It has been suggested that Thiobacillus should be restricted to these autotrophic 

 species and that the facultatively autotrophic species be placed in the genus Psexidomonas. 

 Some heterotrophic species now placed in Pseudomonas are known to have the ability to oxi- 

 dize thiosulfates (Starkey, Soil Sci., 89, 1935, 325). 



The type species is Thiobacillus thioparus Beijerinck. 



Key to the species of genus Thiobacillus. 



I. Thiosulfate oxidized with increa.sed acidity. 



A. Tetrathionate not formed as an intermediate product. 



1. Strictly autotrophic. 



a. Does not oxidize ferrous salts. 



1. Thiobacilhis thioparus. 

 aa. Oxidizes ferrous salts. 



2. Thiobacillus ferrooxidans . 



2. Facultatively autotrophic. 



a. Aerobic. 



b. Does not oxidize free sulfur. 



3. Thiobacillus novellus. 

 bb. Oxidizes free sulfur to sulfate. 



4. Thiobacillus coproliticus . 

 aa. Facultatively anaerobic in presence of nitrate. 



5. Thiobacillus denitrificans . 



B. Tetrathionate formed as intermediate product. 

 1. Final pH, 3.0. 



6. Thiobacillus neopoUtanus. 



* Revised by Dr. C. D. Parker, South Melbourne, Australia, with the assistance of Dr. 

 Kenneth L. Temple, Morgantown, West Virginia, June, 1954. 



