135 



reduction i). In the two foUowing years more extensive publications 

 appeared in which many different aspects of the problem of biological 

 hy drogen sulphide production were discussed 2). 



Beijerinck himself stat es that the direct inducement to his in- 

 vestigations was of an entirely practical nature. In the yeast factory 

 he was confronted with the problem of freeing the canal water used 

 in the steam boilers from the calcium sulphate present in it. It is 

 typical for Beijerinck's originahty that he considered in this 

 technical connection the idea of applying a biological method for 

 sulphate destruction. But it is particularly instructive to see that a 

 problem of such restricted scope led to investigations characterized by 

 an exceptional broadness of conception, and dealing exhaustively with 

 the general significance of biological hydrogen sulphide production in 

 nature. 



In Beijerinck's German publication one reads the following simple 

 sentence: "Die Isolierung des Sulfidfermentes hat mir viel Mühe 

 gekostet". The reasons for his initial failure are then summarised. It is 

 instructive to consider these reasons, because they offer an explana- 

 tion of the most remarkable fact that even nowadays, 45 years after 

 Beijerinck's pioneer work, the number of laboratories in which pure 

 cultures of sulphate-reducing bacteria have been obtained can prob- 

 ably be counted on the fingers of one hand. 



It is probably not an exaggeration to state that until very recent 

 years, sulphate reduction had remained practically a special domain 

 entered only by Dutch and Russian investigators. 



Beijerinck explained that at first he had shared the opinion of the 

 earlier investigators that many of the ordinary aerobic bacteria, oc- 

 curring in soil and in water, which often display a pronounced redu- 

 cing activity towards various dyes, would also be able to reduce 

 sulphate. Many experiments, all leading to negative results, had 

 convinced him of the untenability of this view. Careful microscopical 

 examination of well-devised enrichment cultures made him conclude 

 that sulphate reduction proceeded under the influence of a specific 

 organism which, under certain conditions, at least exhibited a 

 typical spirillum-shape. His earlier experiences with species of Spiril- 

 lum led him to the erroneous conclusion that the sulphate reducing 

 spirillum too would be favoured by a certain concentration of f ree 

 oxygen in the medium. He only gradually realized that the causative 

 organism of sulphate reduction is a strictly anaerobic organism, which 

 in crude cultures, owing to the competition of other bacteria, thrives 

 only in media with low concentrations of simple organic compounds, 

 like lactates, malates, ethyl alcohol, etc. 



Yet, even this insight did not remove all difficulties inherent in the 



») Versl. Kon. Akad. v. Wet. Amsterdam 3, 72, 1894. 



2) Centralbl. f. Bakt. u. Parasitenk. IT, 1, 1, 49 und 104, 1895. Arch. néerl. d. 

 Sciences exactes et naturelles 29, 233, 1896. * ' 



