Microbiology. "On the Occurrence of Sulphate-reduction in the 

 deeper layers of the Earth". Bj C. A. H. \'0n Wolzogrn 

 KüHR. (Coinmniiicated by Prof. G. van Itekson Jr). 



(Communicated at the meeting of April 29, 1922). 



§ 1. Introduction. 



The disa|)[)eaiar)ce of organic matter at greater depths in the soil 

 has since long occupied the minds of investigators. Tiie difficulties 

 associated witli their inquiries regard especially that of obtaining 

 sterile samples from such depths, which is essential to microbiolo- 

 gical inquiry. 



The process of oxidation, which causes organic matter to disappear, 

 can be effected by free as well as by combined oxygen. When the 

 air is shut off, as is the case in tlie lower strata, oxidation is of 

 course brought about by combined oxygen. 



Now the question is iiow this process can take place microbio- 

 logical ly. 



The term sulphate-reduction designates the process by which, 

 with the exclusion of air, organic matter in the soil is oxidized 

 under the influence of combined sulphate-oxygen. This anaerobic 

 process is effected by Microspira desulfuricans, discovered in 1895 

 by Beijkrinck ^). It being an exothermic process energy is set free 

 tlirough this oxidation, which is utilized physiologically by the 

 sulphate reducing spirilla. The rough equation for sulphate-reduction 

 gives the following formula: 



2C . . . + CaSO, + H,0 -^CaCO, + CO, -f H,S, 

 in which C. . . is the symbol for the source o( carbon. 



Microspira desulfuricans occurs in the mud of ditches and the 

 ooze of the Dutch "Wadden". The grey, bluish-black to black colour 

 of the soils in which sid|)hate-reduction takes place, must be ascribed 

 to ferric sulphid, in which form the lil)erated hydrogen sulphid is 

 combined by iron-compounds present in the soil. 



The occurrence of the sulphate-reducing microbe at the greater 

 depths 111 the terrestrial soil has been less frequently observed and. 



1) Ueber Spirillum desulfuricans als Ursache von Sulfalreduktion. Verzamelde 

 Geschriften. 3de deel, pg. 102. 



