Bark microbiota modulate climate-active gas fluxes in Australian forests

Area of Science:

• Microbial Ecology
• Environmental Microbiology
• Biogeochemistry

Background:

• Emerging evidence indicates microbial life on tree bark.
• However, their specific identities, functions, and ecological significance remain largely unexplored.

Purpose of the Study:

• To characterize the microbial communities inhabiting Australian tree bark.
• To investigate the metabolic functions of these microbes, particularly concerning climate-active gases.

Main Methods:

• Gene-centric and genome-resolved metagenomics were employed to analyze bark microbial communities.
• Microcosm experiments were conducted to assess gas metabolism.
• In situ field measurements were integrated to evaluate in planta gas cycling.

Main Results:

• Abundant and specialized microbial communities were identified across eight Australian tree species.
• Predominant bacteria were hydrogen-cycling facultative anaerobes, adapted to fluctuating conditions.
• Bark-associated methanotrophs were abundant and coexisted with methanogens.
• Microbial communities consumed methane, hydrogen, and carbon monoxide under aerobic conditions and produced them under anoxia.

Conclusions:

• Tree bark hosts a diverse microbiome with significant metabolic capabilities.
• These microbial communities actively metabolize multiple climate-active gases within tree stems.
• The identified microbial activity suggests a potentially substantial contribution to global atmospheric gas cycles.