Table 2 H2 partial pressure (pH2), in the 0 °C/7–12 mbar/Mars gas treatment available to M. barkeri compared with reported H2 affinity thresholds§ of †hydrogenotrophic and ^obligately methylotrophic methanogens.

From: Hydrogenotrophic methanogenesis at 7–12 mbar by Methanosarcina barkeri under simulated martian atmospheric conditions

Species

pH2 [mbar]

Reference no.

†*Methanosarcina barkeri str. MS

(+ 0.1 µM Ni)

0.20–0.35

This study

†*Methanosarcina barkeri str. MS

(no added Ni)

0.19

51

†*Methanosarcina barkeri str. MS

(+ 0.2 µM Ni)

0.13

51

†*Methanosarcina barkeri str. MS

0.16

50

†Methanobacterium formicicum str. JF-1

0.06

49

†Methanobacterium bryantii str. M.O.H.

2.9 × 10− 4 to 1.4 × 10− 3

54

†Methanoculleus bourgensis str. MAB1

0.001

51

^Methanosphaera stadtmanae str. MCB-3

0.01

56

^*Methanimicrococcus blatticola str. PA

< 0.001

56

^Methanomassiliicoccus luminyensis str. B10

< 0.001

56

  1. Cytochrome-containing methanogens are indicated by an asterisk (*).
  2. §Note that smaller H2 affinity thresholds indicate the ability to utilize H2 at lower partial pressures.
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