14 BACTERIAL FERMENTATIONS 



So far no methane bacteria preferring acid media have been 

 reported. Nevertheless the slow formation of methane in 

 peat bogs having a pH as low as 4.0 suggests that acid 

 tolerant species probably exist. 



Taxonomy. The system of classifying methane bacteria 

 depends upon the relative importance given to morphology 

 and physiology. The editors of Bergey's Manual of Deter- 

 minative Bacteriology 21 have placed primary emphasis upon 



TABLE 4 



Classification of Methane Bacteria 



Family : M ethanobacteriaceae 



A. Rod-shaped cells 



I. Non-sporulating : Methanol acterium 



1 . Mbact. formicicum : formate, carbon monoxide, hydrogen 



2. Mbact. propionicum : propionate 



3. Mbact. sohngenii: acetate, butyrate 

 II. Sporulating: Methanobacillus 



1. Mbac. omelianskii: primary and secondary alcohols, hy- 

 drogen 



B. Spherical cells 



I. Cells not in sarcina arrangement: Methanococcus 



1. Mc. mazei: acetate, butyrate 



2. Mc. vannielii'. formate, hydrogen 



II. Cells in sarcina arrangement: Methano sarcina 



1. Ms. barkerii: methanol, acetate, carbon monoxide, hydro- 

 gen 



2. Ms. methanica: acetate, butyrate (?) 



morphology, and consequently have dispersed the methane 

 bacteria among the families and genera of better-known 

 bacteria of similar forms. In contrast, those investigators 

 who have had personal experience with the methane bac- 

 teria have been impressed by the striking physiological 

 characteristics of all members of the group, and have pre- 

 ferred to think of them as belonging to a physiological 



