Thomas, D. N. | bioRxiv Science

bioRxiv2026

Northern palsa and peat ecosystem microbiomes are potentially supported by hydrogen and carbon monoxide metabolism

Northern peatland and permafrost ecosystems are facing rapid changes, with increasing temperatures, permafrost thaw and shifts in hydrology. Characterizing microbial communities and metabolic potential from the soils and associated water bodies is crucial to understanding the changes in biogeochemical cycling in these ecosystems. For this, samples were collected and sequenced from subarctic palsa and peat soils, along with samples from associated thaw ponds and streams. Metagenomics was utilized in describing the microbiome and its metabolic potential in these environments. Palsa soils hosted microbial communities that were distinct from the peatland soils, ponds and stream waters. Soils and their adjacent ponds shared taxa, and peat soils and ponds also shared taxa with the streams, unlike palsa soils which were likely more hydrologically isolated. Based on metabolic marker gene ratio for denitrification [(nirS+nirK)/nosZ], palsa soils had the strongest potential to be a source of nitrous oxide (N2O) out of all the sample types. Marker genes for hydrogen gas (H2) and carbon monoxide (CO) utilization were abundant across soil environments and metagenome assembled genomes, suggesting that trace gas oxidation is likely one of the key energy sources for microbiomes. In the palsa ponds and peat soils pmoA, marker gene for methanotrophy, was the most abundant compared to the other sample types.

microbiology↗

bioRxiv2025

Biodegradation of different bioplastics by specialised microbial communities in a coastal brackish environment

Microorganisms are metabolically versatile and central to marine ecosystems, yet the potential of marine microbial communities to degrade different bioplastics and the effect of environmental factors are poorly understood. Employing multi-seasonal in situ and in vitro experiments, we assessed the biodegradation of six commonly used bio-based bioplastic materials at a coastal site in the brackish Baltic Sea and characterised the associated microbial communities using metagenomics and metatranscriptomics. Cellulose acetate (CA), polybutylene succinate (PBS), and polyhydroxybutyrate/valerate (PHB) degraded at varying rates across materials, seasons, and experimental settings, with up to 28% weight attrition after 97 weeks in situ (CA) and 56% carbon loss to CO2 after four weeks in vitro (PBS). The three biodegraded plastics developed similar microbial communities that differed markedly from those on the other materials (cellulose acetate propionate, polyamide, and polyethylene) and in the water column. The main microbial populations on the biodegraded plastics included aerobic and facultative anaerobic heterotrophs with a broad capacity for carbohydrate metabolism. Populations with the potential for nitrogen fixation and denitrification were more prevalent on the biodegraded plastics, suggesting a link with the marine nitrogen cycle. Based on the metatranscriptomic signal of key genes involved in the initial hydrolysis of CA, PBS, and PHB, we identified diverse microbial populations that can potentially drive the biodegradation of these materials in the Baltic Sea, many of which encoded the potential to degrade multiple bioplastics. We propose the term bioplastisphere to denote the distinctive microbial communities associated with biodegradable plastics.

microbiology↗