220 



METABOLISM 



Henneberg. 1898. Koch's Jahresbericht, 9, 249 and 251. 



HoYER. 1898. Rev. in Koch's Jahresbericht, 9, 242. 



Knecht. 1901. Centrbl. Bakt. II, 7, 165. 



Klocker. 1901. Centrbl. Bakt. II, 7, 152. 



[KosTYTSCHEW. 1904. Jahrb. f. \viss. Bot. 40, 563.] 



Laborde. 1899. Compt. rend. Paris, 129, 344. (Koch's Jahresbericht, p. 98.) 



Maze. 1900. Annales Instit. Pasteur, 14, 350. 



[MAzife. 1904. Annales Instit. Pasteur, 18, 535.] 



[Nabokich. 1903. Ber. d. bot. Gesell. 21, 467.] 



Omelianski. 1902. Centrbl. Bakt. II, 8, 193. 



Omelianski. 1903. Ibid. II, 11, 177.] 



Omelianski. 1904 a. Ibid. II, 11, 369.] 



Omelianski. 1904 b. Ibid. II, 12, 33.] 



I'asteur. 1859. Annales de chim. et de phys. Ill, 58, 347. 

 [f'ASTEUR. 1861. Compt. rend. 52, 344 ; 1863, 56, 416 and 734. 

 Stoklasa, Jelinek and Vitek. 1903. Beitr. z. chem. Phys. u. Path. 3, 460. 

 Traube, E. 1858. Theorie der Fermentwirkungen. Berlin. 

 Udranszki. 1889. Zeit. f. phys. Chem. 13, 539. 

 Wehmer. 1905. Centrbl. Bakt. II, 14, 556. 

 Winogradsky. 1895. Compt. rend. Paris, 121, 742. 

 WoRTMANN. 1892. Landw. Jahrb. 21, 901. 

 WoRTMANN. 1898. Ibid. 27, 631. 

 WoRTMANN. 1902. Weinbau u. Weinhandel. 



LECTURE XVIII 

 SULPHUR AND NITROGEN BACTERIA 



At the conclusion of our last lecture we noted that the sulphur of the 

 proteid molecule was set free as sulphuretted hydrogen in the course of putre- 

 faction. There are, however, other processes in nature in which sulphuretted 



hydrogen is also developed. In 

 many of these also micro-organisms 

 are concerned, such as in the re- 

 duction of sulphates, which is 

 carried out with tolerable com- 

 pleteness not only by the strictly 

 anaerobic Spirillum desulphuri- 

 cans (Beijerinck, 1895), but also 

 by other less exclusively anaerobic 

 forms (Beijerinck, 1900). We 

 are unable, however, to explain 



Fig. 39. Sulphur-bacteria, a-c, Beggiatoa, x looo. rf, Chro- what SCrvicC SUCh TcductionS are 

 X 500. After Fischer, Vori. ub. Bakt 2nd edit. to thcSC Bactcria. [AcCOrdmg tO 



Delden (1903) it consists in the 

 gain of oxygen from the sulphates, just as, in the other reduction processes 

 (p. 232), oxygen is obtained from compounds containing it.] In any case it is 

 not our purpose to enter into a detailed discussion of these processes ; what 

 we are interested in at the moment is merely the final product, especially 

 the sulphuretted hydrogen, and the further alterations it undergoes under 

 the influence of certain Bacteria, which for that reason have received the 

 name of ' sulphur-bacteria '. 



We may select as our first example of sulphur-bacteria, the genus Beg' 

 giatoa (Fig. 39, a), which may be described briefly as a colourless Oscillaria, in 

 whose protoplasm plentiful aggregations of sulphur particles or drops may be 

 found. The presence of such large quantities of pure sulphur in its cells leads 

 us to conclude that the sulphur plays an important part in the life of the 



