Differences down-under: alcohol-fueled methanogenesis by archaea present in Australian macropodids

Area of Science:

• Microbiology
• Animal Science
• Biochemistry

Background:

• Australian macropodids have a unique foregut microbiota linked to lower methane emissions.
• Methanogenic archaea exist in macropodid foreguts, but their roles are poorly understood.

Purpose of the Study:

• To investigate the metabolic capabilities of a novel methanogenic archaeon isolated from a kangaroo's foregut.
• To understand the genomic and metabolic basis for the persistence of these archaea in herbivores with reduced methane output.

Main Methods:

• Isolation and taxonomic assignment of archaea from Western grey kangaroo (Macropus fuliginosus) foregut contents.
• Genomic analysis of Methanosphaera sp. WGK6 and comparison with human gut isolate Methanosphaera stadtmanae DSMZ 3091(T).
• In vitro growth studies using different substrates (methanol, ethanol, hydrogen) to assess metabolic pathways.

Main Results:

• Methanosphaera sp. WGK6 was identified as a methylotroph capable of utilizing ethanol primarily as a reducing agent.
• The WGK6 genome contains unique genes for alcohol and aldehyde dehydrogenases absent in M. stadtmanae DSMZ 3091(T).
• Ethanol supported greater cell yield per mole of methane compared to hydrogen, suggesting enhanced metabolic efficiency.

Conclusions:

• The expanded metabolic versatility, particularly ethanol utilization via specific dehydrogenases, explains the persistence and abundance of Methanosphaera archaea in kangaroo foreguts.
• These findings contribute to understanding the microbial ecology of low-methane-emitting herbivores.