Even carbon-eating bacteria quietly sip some CO2 too
Brown EK, Pulliam K, Weeks K, Harris CM, Leavitt WD
Soil Health
The soil microbes breaking down compost and mulch in your garden beds aren't just processing organic matter, they're also pulling in a sliver of dissolved carbon dioxide, and that hidden habit shifts with temperature and how much food is available to them, which matters for anyone thinking about how healthy soil locks away carbon.
Most bacteria get their carbon by eating organic stuff, like sugars or dead plant matter, rather than making it from air like plants do. This study found that even these 'eater' bacteria grab a small extra bit of dissolved carbon dioxide from their surroundings, and they do it more when temperatures are just right and food is scarce. It's a small effect, but it means the usual story of who fixes carbon in soil and oceans is a bit more complicated than we thought.
Key Findings
Two heterotrophic bacteria (Pseudomonas putida from soil, Pseudoalteromonas carrageenovora from marine environments) incorporated 13C-labeled dissolved inorganic carbon into their biomass across all tested conditions, ranging from 0.006%-0.029% in P. putida to 0.18%-1.1% in P. carrageenovora.
Inorganic carbon fixation was highest during exponential growth phase, at optimal (warmer) growth temperature, and under low organic carbon availability, consistent at both bulk and single-cell levels.
The measured contribution falls at or below the low end of prior estimates (1%-8%) for anaplerotic carbon fixation in heterotrophs, suggesting this process is often undetectable without sensitive stable isotope probing techniques.
chevron_right Technical Summary
Bacteria that live on organic matter, not sunlight or inorganic carbon, still pull in trace amounts of dissolved inorganic carbon to build their bodies, and how much depends on temperature and how much food is around. The effect is tiny but real, and it means scientists tracking carbon in oceans and soil may need to account for it.
Abstract Preview
Original paper
Heterotrophic inorganic carbon fixation varies with temperature and resource availability in marine and soil bacterial isolates.
Inorganic carbon use in cellular metabolism is ubiquitous in all living organisms. The assimilation of inorganic carbon into biomass via heterotrophic inorganic carbon fixation (HICF) is estimated ...
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