284 THE SULPHUR BACTERIA 



abundance in natural waters containing sulphuretted hydrogen, and are, on the 

 other hand, almost entirely lacking elsewhere in Nature, he came to the opinion 

 that this gas is produced by the reducing action of these fission fungi on the 

 sulphates in the water, and that they subsequently reoxidise the gas, sulphur 

 being left as a deposit in the cells. In forming this opinion he was chiefly 

 influenced by the result of an investigation made by LOTHAR MEYER (I.), who 

 kept a sample of sulphur-spring water (rich in Beggiatoa) from Landeck in 

 Silesia for four months in a stoppered flask, and found that at the end of that 

 time it contained five times as much H 2 S as at first. The same conclusion as 

 deduced by Conn was also arrived at by JE. PLAUCHU (I.), and by A. ETARD and 

 L. OLIVIER (I.). This hypothesis, which credited the sulphur bacteria with 

 both a reducing and an oxidising capacity, was first thoroughly investigated in 

 1886 by S. WINOGRADSKY (VI.), who showed that the sulphur bacteria consume 

 (instead of producing) sulphuretted hydrogen ; oxidising it and storing up the 

 separated sulphur in their cells. The amount of these enclosures in the cell is 

 larger or smaller according as this process can be carried on with a greater or 

 lesser degree of vigour. It depends, therefore, on external conditions, and 

 consequently cannot be relied on as was done previously by various observers : 

 inter alia, Winter in Rabenhorst's " Kryptogamen Flora " and by Engler as 

 a characteristic for the differentiation of species. The sulphur does not 

 permanently remain in the cells, but is oxidised by them to sulphuric acid, the 

 latter being then absorbed by the carbonates usually CaH 2 (C0 3 ), in the 

 water, and converted into sulphates. 



If these Schizomycetes are deprived of sulphuretted hydrogen for a long time, 

 they consume their internal store of sulphur (which will be exhausted in twenty- 

 four to forty-eight hours), and then perish of hunger. This fact demonstrates 

 that the sulphur bacteria cannot permanently dispense with sulphuretted 

 hydrogen, but that this gas is actually their special (and almost exclusive) source 

 of energy. Sulphur, or rather its compound with hydrogen, plays the same part 

 towards these organisms as the carbohydrates do towards the majority of Schizo- 

 mycetes ; its combustion liberates the energy necessary to the maintenance of 

 their vitality. According to the observations of Winogradsky, the individual 

 threads of Beggiatoa daily consume from two to four times their own weight of 

 the gas. These Schizomycetes require but little other (organic) nutriment, and in 

 fact will not stand very much. This explains, on the one hand, their unusually 

 slow rate of growth in proportion to the amount of sulphur separated, and, on 

 the other, their inability to grow in the ordinary nutrient media employed in 

 bacteriology : e.g. on gelatin they perish in a very few minutes. Attempts to 

 grow them as pure cultures on a large scale have hitherto failed, and the 

 physiological facts determined concerning them have all had to be ascertained 

 very laboriously by cultivating single organisms in sulphur-water on microscope 

 slides. 



The optimum, i.e. the maximum supportable, quantity of sulphuretted 

 hydrogen in the water is higher in the case of the red sulphur bacteria than 

 with the colourless, filamentous species. These latter require less, and in fact 

 die instantly if placed in water saturated with the gas, whereas the red kinds 

 will stand this degree of concentration very well. Consequently, under natural 

 conditions, these latter will gain the upper hand in such places where large 

 quantities of sulphuretted hydrogen are evolved, either as a result of the decom- 

 position of an abundance of organic matters (albumen) or by the powerful 

 reduction of sulphates. This is the case, for example, in the stagnant shallow 

 bays on the Danish Zeeland coast, and the same conditions obtain in the 

 Limanes so plentiful along the coast of the Black Sea (e.g. near Odessa). These 

 latter are shallow salt lakes, separated from the open sea merely by a low, 



