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Anoxygenic photoautotrophy driven by humus and microplastics in a photosynthetic bacterium
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Researchers discovered an unexpected role for microplastics in carbon cycling: when certain plastics like PLA and PET are present alongside humic substances in sunlit, oxygen-free environments, they can accelerate the growth of photosynthetic bacteria by acting as electron donors. This means microplastics are not merely passive pollutants in aquatic sediments — they may actively influence microbial communities and carbon dynamics in ways not previously understood. The finding adds a new dimension to understanding how plastic pollution reshapes the chemistry of natural ecosystems.
Humus and microplastics are recalcitrant organics in soils and aquatic systems, and their role in the geochemical cycling of elements remains elusive. Herein, we have identified a new mechanism by which humus and microplastics participate in anoxic carbon cycling. We demonstrated that the photoexcitation of 5-30 mg/l of humic acid or fulvic acid, two major fractions of humus, can drive CO2 fixation and enable the photoautotrophic growth of a photosynthetic bacterium, Rhodopseudomonas palustris. This process was enhanced by 10.69%-144.87% upon the addition of 100 mg/l of poly(lactic acid) or poly(ethylene terephthalate). Mechanistic investigations demonstrated that the microplastics act as sacrificial quenchers during humus photoexcitation, leading to their depolymerization. Transcriptomic analyses revealed high expression of genes encoding extracellular electron uptake pathways including extracellular cytochrome c and its oxidases in the photoautotrophic growth of R. palustris. This study expands our understanding of how humus and microplastics are involved in the biogeochemical cycling of carbon and sheds light on how they impact the CO2 dynamic fluxes in sunlit anoxic environments.
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This review examines how photosynthetic microorganisms like algae and cyanobacteria can break down microplastics using sunlight as their energy source. These organisms naturally colonize plastic surfaces and some can produce enzymes that degrade common plastics like PET. The research highlights a promising biological approach to cleaning up microplastic pollution in water and soil, which could ultimately reduce the amount of plastic entering the food chain and human bodies.
Microplastics: New substrates for heterotrophic activity contribute to altering organic matter cycles in aquatic ecosystems
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This study demonstrated that heterotrophic bacteria colonizing microplastic surfaces in aquatic ecosystems have distinct metabolic capabilities and can process organic matter at rates different from planktonic bacteria. The findings suggest that the plastisphere — the microbial community on plastic surfaces — may alter organic matter cycling in aquatic environments as microplastic abundance grows.
Microplastics Reshape the Fate of Aqueous Carbon by Inducing Dynamic Changes in Biodiversity and Chemodiversity
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Researchers found that microplastics reshape aqueous carbon cycling by releasing chemical additives that inhibit autotrophic bacteria, promoting CO2 emissions, and stimulating microbial metabolic pathways that transform dissolved organic matter into more stable, less bioavailable forms.
Microplastics a Novel Substratum for Polyhydroxyalkanoate (PHA)-Producing Bacteria in Aquatic Environments
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Researchers investigated microplastic surfaces as a novel habitat for bacteria that produce polyhydroxyalkanoates (PHA), a biodegradable natural plastic. They isolated PHA-producing bacteria from microplastic-colonizing communities, suggesting microplastics in aquatic environments may inadvertently support bacteria capable of producing sustainable plastic alternatives.
Microplastic accelerate the phosphorus-related metabolism of bacteria to promote the decomposition of methylphosphonate to methane
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Researchers found that microplastics accelerate phosphorus-related metabolism in marine bacteria, promoting the decomposition of methylphosphonate to methane in oxygenated water and revealing a previously unknown mechanism linking plastic pollution to greenhouse gas production.
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When a large batch of papers lands in the Atlas, we read through it and send a short write-up of what stood out.