68 VETERINARY BACTERIOLOGY 



Beggiatoa and similar organisms whose cells will be found packed 

 with sulphur granules. Probably the following reaction accounts 

 for this formation of free sulphur: 



2H 2 S + O 2 = 2H 2 O + S 2 . 



The process is carried still farther if there is any deficiency of 

 the hydrogen sulphid, and the free sulphur is converted into 

 sulphuric acid and sulphates. 



S 2 4- 3O 2 = 2SO 3 

 H 2 O + SO 3 = H 2 SO 4 . 



The sulphuric acid is, of course, at once neutralized by the bases 

 present in the water. 



Oxidation of Iron. Many natural waters contain ferrous car- 

 bonate or some similar salt of iron. Certain bacteria oxidize 



Fig. 35. Microorganisms that oxidize ferrous to ferric iron: a, Lep- 

 tothrix ochracea; b, Gallionella ferruginea; c, Spirophyllum ferrugineum . 

 (Adapted from Ellis.) 



this to ferric hydrate, and deposit this insoluble material in 

 their sheaths. The reaction may be represented as follows: 



2Fe 2 C0 3 + 3H 2 4- O = F ej (OH) 6 4- 2CO 2 . 



Probably these organisms make use of the energy obtained by 

 this reaction in the same manner that the sulphur bacteria do the 

 oxidation of the sulphur, to secure energy for the formation of their 

 foods and to gain the energy needed for growth ;m<l development. 

 These organisms are particularly apt to occur in well water or 

 spring water laden with iron, and have in some cases caused 

 considerable trouble by clogging the water pipes with 1 heir growth. 

 It is known that the bog iron ore of Sweden and probably the 



