54 



SULPHUR BACTERIA 



dark warm room. After some time a smell of HgS was noticed, 

 and a thick scum collected on the surface. The scum contained 

 Beggiatoa alba and other colourless bacteria. Gypsum was 



added periodically to increase 

 the growth. This method has 

 been tried by Molisch, by 

 Bavendamm, and by the pres- 

 ent writer, but without suc- 

 cess. 



(b) Macerated Hay and Gyp- 

 sum supplied another medium. 

 The hay was placed in water 

 for ten days and then boiled. 

 The water was then decanted, 

 a fresh supply added, and this 

 again boiled. This process was 

 repeated several times and the 



Fig. 3. 



(a) Floor covered with damp paper 

 on which the glass slide rests 

 between observations. 



{b) Small dish containing water to 



which I gram calcium sulphide hay allowed to decompose in 



has been added. 



water 



(c) Wide tube for occasional addi- 



tion of a few drops of weak 

 hydrochloric acid. 



(d) Small tube to facilitate the addi- 



tion of liquids down tube c. 

 Winogradsky regarded the sul- 

 phur bacteria as almost com- 

 pletely autotrophic* Reused 



Beggiatoa alba appeared 

 early. 



(c) Glass Slide Preparations. 

 — The material was placed 

 under a coverslip, prevented 



Strassburg tap water to which from drying up, and supplied 

 0005 — o-oio per cent, calcium . . 



periodically with Hgo. ihe 



butyrate, or sodium acetate, 

 had been added, or water from 

 a sulphur well to which small 

 amounts of HjS had been added. 

 Since he considered the sulphur 

 bacteria to be almost completely 

 autotrophic, he added only min- 

 ute quantities of organic matter. 

 He found the organisms to live 

 up to nineteen days if ad- 

 equately supplied with sulphur- 

 etted hydrogen, bnt only eight 

 or nine days in its absence. 



apparatus is shown in the 

 accompanying diagram (Fig. 3). 



(d) Large scale experiments 

 carried out by method [c] were 

 also successful. 



His conclusions are as fol- 

 lows : — 



1. Sulphuretted hydrogen is absorbed, oxidized first to 



sulphur and then to sulphate. 



2. The bacteria die if cultivated without sulphuretted 



hydrogen. 



* An aulotrophic organism is one which is independent of organic matter 

 in its nutrition. 



