FAMILY XIII. BACILLACEAE 



693 



Habitat: Found in soil and in naturally 

 retting plant materials. 



Nolc: Species incerlae sedis. The relation- 

 ships of Melhanohaclerium soehngenii Barker 

 and Methanobacterium omelianskii Barker to 

 other species of bacteria are not entirely- 

 clear. M. soehngenii, a non-motile, non- 

 sporeforming, Gram-negative species, has 

 tentatively been placed in the family Spiril- 

 laceae. While M. omelianskii was described 

 for some time as being non-motile and non- 

 sporeforming, it was later found to be defi- 

 nitely motile at times, to form spores and 

 to be Gram- variable. As an anaerobe, it 

 should be placed in the genus Clostridium. 

 If, however, it were placed in the genus 

 Clostridium, it could not bear the specific 

 epithet omelianskii, as this epithet is pre- 

 empted by the cellulose-fermenting Clos- 

 tridium omelianskii (Henneberg, emend. 

 Clausen) Spraj', a different organism. While 

 awaiting a better determination of the rela- 

 tionships of Methanobacterium omelianskii, 

 this organism has been placed here. 



1. Methanobacterium omelianskii 



Barker, 1936. (Bacille de la decomposition 

 methanique de I'alcohol ethylique, Omelian- 

 sky, Ann. Inst. Past., 30, 1916, 56; Barker, 

 Arch. f. Mikrobiol., 7, 1936, 436; also see 

 Antonie van Leeuwenhoek, 6, 1940, 201; and 

 Jour. Biol. Chem., 137, 1941, 153.) 



o.me.li.an'ski.i. M.L. gen. noun omelian- 

 skii of Omeliansky; named for Prof. W. 

 Omeliansky, the Russian bacteriologist who 

 was the first to observe this organism. 



Rods, 0.6 to 0.7 by 1.5 to 10.0 microns, 

 usually 3.0 to 6.0 microns in length. Origi- 

 nally described as non-sporeforming (Omel- 

 iansky, op. cit., 1916, 60; Barker, op. cit.. 



1936, 437), this organism was later found to 

 form spores of low heat resistance which 

 are spherical and terminal and which swell 

 the cells (Barker, op. cit., 1940, 207). Ini- 

 tiall}^ reported as non-motile (Barker, op. 

 cit., 1936, 437) but later observed to be oc- 

 casionally and feebly motile, the type of 

 flagellation not determined (Barker, op. 

 cit., 1940, 207). At first described as Gram- 

 negative (Barker, op. cit., 1936, 437), the 

 cells were later reported to be Gram-var- 

 iable (Barker, op. cit., 1940, 208). 



Primary alcohols, including ethanol, pro- 

 panol, n-butanol and n-amyl alcohol, are 

 oxidized to the corresponding fatty acids. 

 Secondary alcohols, including isopropanol 

 and sec-butanol, are oxidized to the corre- 

 sponding ketones. Hj-drogen is oxidized. 



Ethanol is utilized the best of all organic 

 compounds. 



Carbon dioxide is utilized and converted 

 to methane. Growth and alcohol oxidation 

 are directly proportional to the carbon diox- 

 ide supply, at low concentrations. 



Fatty and hydroxy acids, glucose and 

 other polyhydroxy alcohols and amino acids 

 are not attacked. 



Ammonia is utilized as a nitrogen source. 



Nitrate, sulfate and oxygen cannot be 

 used as oxidizing agents. 



Obligate anaerobe. 



Optimum temperature, between 37° and 

 40° C. Maximum, between 46° and 48° C. 



Growth limits, pH 6.5 and 8.1. 



Source: Isolated from soil, fresh-water 

 and marine muds, rabbit feces and sewage. 

 Pure cultures were isolated from fresh-water 

 and marine muds (Barker, op. cit., 1940, 

 201). 



Habitat: Found wherever organic matter 

 is decomposing in an anaerobic, approxi- 

 mately neutral environment. 



