Antibiotic resistance is widely recognized as one of the greatest global public health threats, but scientists are now uncovering an unexpected contributor to the problem living quietly in rivers, lakes, and coastal waters. A new review highlights how microalgae, microscopic photosynthetic organisms that support aquatic food webs, may also help concentrate and spread antibiotic resistance genes in natural water environments.
The study, published in the journal Biocontaminant , synthesizes emerging research showing that microalgae create microenvironments that can foster the growth and transmission of antibiotic resistance genes, often abbreviated as ARGs. These genes allow bacteria to survive antibiotic treatment and are a key driver of antimicrobial resistance worldwide.
“Microalgae are essential to aquatic ecosystems and play a fundamental role in carbon fixation and oxygen production,” said corresponding author Qing Wang. “However, our review shows that the microscopic environment surrounding algal cells can also become a hotspot where antibiotic resistance genes accumulate and spread.”
Microalgae live in close association with bacteria in a region known as the phycosphere, a nutrient-rich microenvironment surrounding algal cells. Within this zone, algae release organic compounds that attract bacteria and promote microbial growth. While this interaction supports ecological balance, researchers have found that it also creates favorable conditions for bacteria carrying resistance genes to thrive.
According to the review, the phycosphere can act as a reservoir for antibiotic resistance genes. Studies have shown that the abundance of these genes around certain freshwater microalgae can be dramatically higher than in the surrounding water. Dense microbial populations and protective biofilm structures formed by extracellular polymeric substances help bacteria survive and exchange genetic material more efficiently.
“This environment increases contact between bacterial cells and enhances horizontal gene transfer, which is one of the main mechanisms that allows antibiotic resistance genes to spread between microorganisms,” Wang explained.
The research also highlights how environmental stressors can amplify this problem. Nutrient pollution, rising temperatures, and antibiotic residues from human and agricultural activities can stimulate algal growth and alter microbial communities. These changes can increase the abundance of resistance genes and accelerate their transmission.
For example, algal blooms fueled by nutrient pollution can create ideal conditions for bacterial colonization. During bloom events, researchers have observed significant increases in resistance gene abundance compared to non-bloom conditions. Additionally, low concentrations of antibiotics in water bodies may unintentionally encourage bacteria to develop and share resistance mechanisms over time.
Other emerging contaminants, including microplastics and heavy metals, may further complicate the situation. Microplastics can serve as surfaces where microbial communities form and interact, potentially increasing gene transfer. Meanwhile, certain heavy metals can influence bacterial biofilm formation and indirectly affect resistance gene dynamics.
Despite growing evidence, scientists emphasize that research into microalgae-mediated antibiotic resistance remains at an early stage. Many questions remain about how resistance genes move between algae, bacteria, and surrounding environments under real-world conditions.
“Our findings highlight a hidden ecological pathway contributing to antimicrobial resistance,” Wang said. “Understanding how these genes move through aquatic ecosystems is critical for developing strategies to reduce environmental and public health risks.”
The authors suggest that future research should focus on tracking resistance gene transmission in complex natural ecosystems and developing advanced monitoring technologies. Improved understanding of the phycosphere could help scientists design more effective strategies to manage water pollution and limit the environmental spread of antibiotic resistance.
As antibiotic resistance continues to rise globally, the study underscores the importance of viewing the problem through an environmental lens. The interactions between microscopic organisms in aquatic ecosystems may play a larger role in resistance transmission than previously recognized, offering both new challenges and opportunities for mitigation.
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Journal reference: Sun S, Chen C, Wang J, Sun Y, Wang Q. 2026. Microalgae in the enrichment and spread of antibiotic resistance genes in watersheds: a review. Biocontaminant 2: e003 doi: 10.48130/biocontam-0025-0028
https://www.maxapress.com/article/doi/10.48130/biocontam-0025-0028
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Biocontaminant (e-ISSN: 3070-359X) is a multidisciplinary platform dedicated to advancing fundamental and applied research on biological contaminants across diverse environments and systems. The journal serves as an innovative, efficient, and professional forum for global researchers to disseminate findings in this rapidly evolving field.
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Microalgae in the enrichment and spread of antibiotic resistance genes in watersheds: a review
4-Feb-2026