THE MICROBIOLOGICAL FORMATION OF SULPHUR IN CYRENAICAN LAKES 



K.R.^Butlin and J.R. Postgate 

 {Chemical Research Laboratory, D.S.I.R., Teddington) 



The importance of sulphate - reducing bacteria (Type name : Desulphovibrio desul- 

 phuricans) in the formation of non- volcanic deposits of sulphur has been recognised 

 by geologists and microbiologists for many years. It is thought that the organisms 

 reduced sulphates to sulphides, which were then oxidised to sulphur by chemical or 

 microbiological processes, or by a combination of both. Hunt (1915) attributed the for- 

 mation of the Sicilian deposits to bacterial sulphate reduction in marine conditions 

 similar to those existing in the Black Sea. Schneegans (1935) discussed the function 

 of sulphate reducers in the formation of some French deposits. The great Texas and 

 Louisiana deposits are said to be the result of microbiological sulphate reduction (Zo- 

 Bell, 1936), though the evidence is necessarily speculative. More direct evidence was 

 obtained by Subba Rao, lya & Sreenivasaya (1947) and Subba Rao (1951). They at- 

 tributed the formation of the sulphur in sulphur- bearing clays (27- 35% sulphur) in cer- 

 tain coastal areas of India to the catalytic oxidation of sulphide by atmospheric oxy- 

 gen in the presence of iron. They conducted field trials using cultures of sulphate re- 

 ducers isolated from the sulphur- containing clay, and demonstrated the formation of 

 sulphur in near- natural conditions. Murzaev (1950) discussed the microbiological pro- 

 duction of free sulphur in the muds of Russian lakes and suggested experiments to 

 stimulate its formation. 



Mancuso (1939) studied the geochemistry of an area in the Libyan desert south 

 and west of El Agheila characterized by salt marshes and many small saline lakes. He 

 described one lake, Ain-el- Braghi, in some detail ; it differed from the other lakes 

 examined by him in being fed by a warm sulphur spring (32- 34°C). He noted the abun- 

 dant escape of hydrogen sulphide, which he attributed to the reduction of calcium sul- 

 phate by 'sulphur bacteria'. Some of the hydrogen sulphide was oxidised to finely - 

 divided sulphur which gave the lake a characteristic milky -white appearance. The 

 sulphur slowly settled on the bottom to form a deposit. 



In January 1950 we received a report by Pinfold & Gee (1949) on sulphur- produc- 

 ing lakes about 20 miles south west of El Agheila. It seemed probable that a detailed 

 examination of these lakes would be of scientific interest from the point of view of the 

 processes involved in the formation of natural sulphur deposits, and might give infor- 

 mation and cultures useful in working out an industrial process for sulphur production. 

 We visited the area in May 1950 and examined four lakes {Chemistry Research 1950,). 

 1951). 



The Sulphur- Producing Lakes 



The four lakes examined were: (1) Ain- ez- Zauia, (2) Ain- el- Braghi, (3) Ain- 

 el - Rabaia, (4) Ain - umm - el - Gelud. 



These lakes lie in a stretch of salt marsh running for about 30 miles in a S.E. 

 direction from a point 30 miles W. of El Agheila, which is in the S.E. corner of the 

 Gulf of Sirte 200 miles S.W. of Benghazi. We camped near Ain- ez- Zauia for two 



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