By combining metagenomics with isotope-tracing experiments, the scientists found that Cyanobacteria—well known for fixing carbon dioxide and nitrogen—also act as major reservoirs and regulators of ARGs in estuarine biofilms.
Antibiotic resistance genes are increasingly recognized as environmental pollutants because they enable microorganisms to survive antimicrobial exposure and potentially transfer resistance traits to pathogens. Estuaries, where rivers meet oceans, receive large inputs of nutrients, pollutants, and antibiotics from human activities, making them hotspots for microbial interactions and gene exchange. Previous studies identified nutrients such as nitrogen and organic carbon as factors influencing ARG abundance, yet the biological mechanisms behind these relationships remained unclear. In particular, whether core microbial metabolic pathways—especially carbon fixation and nitrogen cycling—directly shape ARG distribution had not been experimentally verified.
A study (DOI: 10.48130/ebp-0025-0021) published in Environmental and Biogeochemical Processes on 21 January 2026 by Yi Yang’s team, East China Normal University, reveals that carbon and nitrogen metabolic processes are closely intertwined with antibiotic resistance dynamics, suggesting that fundamental ecological functions may unintentionally influence the persistence and dissemination of resistance genes in natural waters.
Using an integrated methodological framework combining metagenomic sequencing, environmental factor analysis, network correlation modeling, large-scale comparative dataset analysis, and DNA-based stable isotope probing (DNA-SIP) microcosm experiments, the researchers systematically investigated ARG profiles, host distributions, and their relationships with carbon–nitrogen metabolic processes across biofilm, sediment, and water samples from the Yangtze Estuary. Metagenomic analysis identified 342 ARG subtypes with comparable subtype diversity among habitats, yet biofilms exhibited ARG abundances one to three orders of magnitude higher than sediments and water, confirming biofilms as dominant ARG reservoirs, particularly under hypertidal conditions. Community and network analyses revealed that Cyanobacteria dominated ARG hosting in biofilms, while Proteobacteria prevailed in sediments and water. Key resistance genes, including evgS, walK, and pvrR, were highly enriched in biofilms and associated with two-component signal transduction systems linked to biofilm formation and multidrug resistance. Environmental correlation analyses further showed that chlorophyll-a, nitrogen nutrients, and organic carbon—not salinity or pH—were the primary factors shaping ARG abundance, implicating microbial productivity and nutrient cycling in ARG regulation. Functional gene profiling demonstrated significantly higher abundances of carbon fixation and nitrogen metabolism genes in biofilms, with the Calvin cycle and nitrogen fixation explaining 13.3% and 54.1% of ARG variation, respectively, indicating strong metabolic coupling. Cross-regional analyses of 74 external estuarine datasets confirmed consistent positive relationships between ARG abundance and marker genes rbcL and nifH. DNA-SIP experiments using 13C-CO₂ and 15N substrates further verified that active carbon- and nitrogen-fixing microorganisms were major ARG hosts; shifts in microbial composition, particularly reductions in Cyanobacteria and increases in Proteobacteria, directly altered ARG dynamics. Genome reconstruction identified active Cyanobacterial lineages (Microcoleaceae and Geitlerinemaceae), while genomic co-localization analyses revealed ARGs embedded within nitrogen transformation and carbon metabolic pathways, suggesting functional integration between resistance traits and microbial metabolism. Collectively, these results demonstrate that Cyanobacteria-mediated carbon–nitrogen metabolism plays a central role in structuring ARG distribution and persistence in estuarine ecosystems.
This study highlights that antibiotic resistance genes function not only as resistance determinants but also as integral components of microbial ecological metabolism. Cyanobacteria harboring ARGs may simultaneously regulate carbon sequestration and nitrogen cycling, linking antibiotic resistance to key ecosystem processes. While these interactions offer opportunities for improved environmental monitoring and sustainable biotechnological applications, the potential for cyanobacterial blooms to accelerate ARG dissemination underscores emerging ecological and public health risks requiring careful management.
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References
DOI
10.48130/ebp-0025-0021
Original Source URL
https://doi.org/10.48130/ebp-0025-0021
Funding Information
This study was funded by the National Natural Science Foundation of China (Grant Nos 42125102, 42576166, and 42507400), the National Key Research and Development Program of China (Grant No. 2022YFC3105800), and The China Postdoctoral Science Foundation (Grant No. GZB20250575).
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