26 BACTERIAL FERMENTATIONS 



This scheme is to be regarded only as a rough working 

 hypothesis. Undoubtedly the actual reaction mechanism 

 is considerably more complicated. For example, a source 

 of energy, such as adenosine triphosphate, would be required 

 for the reduction of XCOOH to XCHO, and for the meth- 

 ylation of XH by methanol. But these are only matters of 

 biochemical detail that could be worked out once the main 

 pathway is established. At present the most important 

 point to determine is the nature of the hypothetical com- 

 pound XH, which could be a metabolite, as in photo- 

 synthesis, or a coenzyme as in fatty acid oxidation. The 

 possibility must not be overlooked that the one-carbon unit 

 is passed from one carrier to another as its oxidation level 

 changes, so that XH may be not one but several compounds. 



The material presented in this chapter shows that knowl- 

 edge of the biology, physiology, and biochemistry of meth- 

 ane bacteria has developed slowly over a long period of 

 time. Unfortunately this knowledge is still incomplete and 

 superficial in many respects. Much time and effort will be 

 required to bring our understanding of this group to a 

 level comparable with that of many other groups of micro- 

 organisms. 



REFERENCES 



1. Sohngen, N. L., Het ontstaan en verdwijnen van waterstof en 



methaan onder den invloed van het organische leven, disserta- 

 tion, Technical University, Delft, 1906 (J. Vis, Jr., Delft, pub- 

 lisher) . 



2. Bcchamp, E., Ann. chim. phys., 13, 103 (1868) . 



3. Tappeiner, W., Ber. deut. chem. Ges., 15, 999 (1882) . 



4. Popoff, Leo., Arch. ges. Physiol., 10, 142 (1875) . 



5. Hoppe-Seyler, F., Z. physiol. Chem., 10, 201, 401 (1886) . 



6. Omelianski, W., Centr. Bakteriol. Parasitenk., II, 15, 673 (1906) . 



7. Barker, H. A., Arch. Mikrobiol., 7, 420 (1936) . 



