TABLE 3.

Dihydrogen thresholds of methanogens and reductive acetogens from the rumen and other environments.

Microorganism	Environment	H2 threshold (ppm)	References
Methanogens
Methanospirillum hungatei	Sewage sludge	30	Cord-Ruwisch et al. (1988)
Methanobrevibacter smithii	Primary sewage digester	100	Cord-Ruwisch et al. (1988)
Methanobrevibacter arboriphilus	Digested sewage sludge	90	Cord-Ruwisch et al. (1988)
Methanobacterium formicicum	Anaerobic sewage sludge digester	28	Cord-Ruwisch et al. (1988)
Methanococcus vannielii	Marine mud	75	Cord-Ruwisch et al. (1988)
Isolate 10-16B	Rumen	126	Le Van et al. (1998)
Isolate NI4A	Rumen	90 - 92	Boccazzi and Patterson (2011)
Reductive acetogens
Sporomusa termitida	Termite hindgut	∼800	Breznak et al. (1988)
Sporomusa termitida	Termite hindgut	830	Cord-Ruwisch et al. (1988)
Acetobacterium woodii NZ Va 16	Not provided	520	Cord-Ruwisch et al. (1988)
Acetobacterium carbinolicum	Freshwater mud	950	Cord-Ruwisch et al. (1988)
Acetitomaculum ruminis 190A4	Rumen	3830	Le Van et al. (1998)
Two reductive acetogenic isolates	Rumen	∼750	Joblin (1999)
Isolate A2	Rumen	1383–2516	Boccazzi and Patterson (2011)
Isolate A4	Rumen	8007	Boccazzi and Patterson (2011)
Isolate A9	Rumen	1619–66157	Boccazzi and Patterson (2011)
Isolate A10	Rumen	208–1284	Boccazzi and Patterson (2011)
Isolate H3HH	Rumen	1390	Boccazzi and Patterson (2011)