254 



SELMAN A. WAKSMAK AND J. S. JOFFE 



morphologically from the Thiobacillus thioparus. Both organisms 

 use carbonates and bicarbonates as sources of carbon and rapidly 

 lose, on the plate, their ability to grow. 



The following table gives the salient features of organisms 

 belonging to groups 4 and 5. 



Autotrophy. Thiobacillus thiooxidans belongs to the autotro- 

 phic bacteria which derive their energy from inorganic substances, 



TABLE 4 

 Salient features of sulfur oxidizing bacteria, not accumulating sulfur tinthin 



their cells 



Energy 



Size 



Accumulation of sulfur 



outside the cell 



Pellicle formation 



Carbon sources 



Aerobism 



Growth on agar media. 



Motility 



Acid accumulation 



th. thioparus 



(nathanson) 



beijbbince 



HjS, thiosul- 

 fate, sulfur 

 3 by 0.5 u 



+ + + 



+ 

 Carbonates, 



bicarbonates 

 Aerobic 



+ 



+ 

 Active 



TH. DENITRrFICANS 

 BEIJERINCK 



H2S, thiosul- 

 fate, sulfur 

 3 by 0.5 M 



+ + + 



+ 

 Carbonates, 



bicarbonates 

 Anaerobic 



+ 

 + 

 ? 



TH. THIOOXIDANS 

 N. 8P. 



Sulfur, thio- 



sulfate 

 1 by 0.5 /I 

 None 



None 



COj from at- 

 mosphere 

 Aerobic 



± 

 Very strong, 

 pH goes 

 down to 0.6 



and its carbon from the CO2 of the atmosphere. This bacterium, 

 which can derive its carbon from the CO2 of the atmosphere, 

 its energy from inorganic sulfur, its nitrogen from ammonium 

 sulfate and other inorganic salts and whose mineral need is 

 very small, was probably among the very first to start life on 

 our planet. The sulfuric acid formed interacted with the in- 

 soluble silicates, phosphates, carbonates, etc., thus helping to 

 break down the original rock and allowing the hfe of other or- 

 ganisms to follow. This organism or, perhaps group of organisms, 

 together with the nitrifying bacteria may thus have formed the 

 initial step in the organic world, manufacturing organic materials 

 for other forms of Ufe to follow. 



