Aquatic and terrestrial cyanobacteria produce methane

Area of Science:

• Microbiology
• Environmental Science
• Biogeochemistry

Background:

• Methanogenesis, the biological production of methane, has traditionally been considered a strictly anaerobic process exclusively performed by archaea.
• Emerging evidence suggests non-archaeal organisms may contribute to methane production, challenging established paradigms.

Purpose of the Study:

• To investigate the potential for methane production by cyanobacteria, a globally abundant group of photoautotrophs.
• To determine the environmental conditions under which cyanobacteria produce methane and its relationship with photosynthesis.

Main Methods:

• Stable isotope labeling techniques were employed to trace methane production in cyanobacteria across various environmental conditions (marine, freshwater, terrestrial; light/dark; oxic/anoxic).
• Quantification of methane production rates and assessment of its correlation with oxygenic photosynthesis.

Main Results:

• Cyanobacteria were demonstrated to produce methane at substantial rates under diverse conditions, including light, dark, oxic, and anoxic environments.
• Methane production was significantly enhanced during oxygenic photosynthesis, linking it to light-driven primary productivity.
• Cyanobacteria-derived methane contributes to methane accumulation in oxygen-saturated surface waters.

Conclusions:

• Cyanobacteria represent a significant, previously unrecognized source of biogenic methane.
• This finding necessitates a re-evaluation of the global methane budget and the biogeochemical cycles of methane.
• The contribution of cyanobacteria to methane production is likely ancient and may be amplified by global warming-induced increases in cyanobacterial blooms, potentially creating a positive feedback loop for climate change.