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Impaired denitrification of aerobic granules in response to micro/nanoplastic stress: Insights from interspecies interactions and electron transfer processes
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This study found that micro- and nanoplastics in wastewater disrupt the ability of beneficial bacteria to remove nitrogen through a process called denitrification. After 90 days of plastic exposure, the communication system bacteria use to coordinate their activity broke down, leading to an imbalance where some bacteria stopped contributing while still consuming shared resources. This reduced the overall efficiency of biological wastewater treatment, a system many communities rely on to clean their water.
The accumulation of micro/nanoplastics in wastewater significantly hinders denitrification in biological wastewater treatment systems, yet the intrinsic mechanisms are not fully understood. Herein, we combined signal molecule monitoring, electrochemical characterization and multi-omics analysis to investigate how quorum sensing (QS)-mediated microbial interactions influence denitrification in aerobic granular sludge systems. Results showed that after 90-day exposure to micro/nanoplastics, cross-talk between multiple signal molecules significantly declined, thereby disrupting the QS system to opportunely sense changes in the external environment. As a consequence of impaired QS, only 5 species exhibited up-regulation of the genes encoding amino acids and cofactors to sustain cross-feeding, while others, acting as "cheaters", relied on metabolites offered by cross-feeding but without reciprocating. This imbalance resulted in insufficient availability of metabolites, including redox-active metabolites such as riboflavin, and subsequently deteriorated the denitrification electron transfer process. Compared to the control group, the extracellular electron transfer capacity and denitrification electron transfer chain activity decreased to, respectively, 88.08 % and 63.33 % (microplastics-exposure) and 79.64 % and 63.75 % (nanoplastics-exposure), which directly contributed to the decline in nitrogen removal. Overall, this study provided deeper insights into the denitrification in complex microbial communities under the stress of micro/nanoplastics from the perspective of QS-mediated microbial social behavior.
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Mechanistic insights into the impact of multi-dimensional microplastic stress on nitrogen removal by heterotrophic nitrifying-aerobic denitrifying bacteria: A meta-transcriptomic analysis
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Researchers studied how different types of microplastics affect bacteria that are used to remove nitrogen from wastewater. They found that PVC microplastics were particularly disruptive, interfering with enzyme function and gene expression needed for denitrification. The study provides molecular-level insights into how microplastic pollution could undermine biological wastewater treatment systems.
Microplastics shaped performance, microbial ecology and community assembly in simultaneous nitrification, denitrification and phosphorus removal process
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This study found that polystyrene and PVC microplastics disrupted the performance of wastewater treatment systems designed to remove nitrogen and phosphorus, reducing nitrogen removal by up to 10%. The microplastics altered microbial communities, decreased cooperation between beneficial bacteria, and blocked important biological pathways. Since wastewater treatment is a key barrier against pollution reaching drinking water, microplastic interference with these systems could indirectly increase human exposure to harmful contaminants.
Mechanistic insights into superior biofilm formation with heterotrophic nitrification-aerobic denitrification bacteria under polypropylene microplastic stress
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Microplastics are known to mess with the helpful bacteria that treat wastewater and remove nitrogen pollution, but this study found that using a special type of bacteria to "seed" water treatment systems made them much more resistant to this disruption. This matters because as plastic pollution keeps growing, protecting the microbial communities that clean our water is essential for keeping waterways—and the water we eventually drink—free of excess nitrogen pollution.
Molecular mechanism of anammox granular sludge disintegration caused by polyethylene terephthalate micro/nanoplastics: a new perspective based on quorum sensing
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Tiny plastic particles from PET plastic (the kind used in water bottles) can break down the beneficial bacteria communities that wastewater treatment plants rely on to remove harmful nitrogen compounds, by disrupting the chemical signals bacteria use to "talk" to each other and stick together. This matters because as microplastic pollution increases, it could weaken our ability to properly treat wastewater, potentially allowing more nitrogen pollution and untreated contaminants to reach our water supplies and environment.
Mechanisms underlying the detrimental impact of micro(nano)plastics on the stability of aerobic granular sludge: Interactions between micro(nano)plastics and extracellular polymeric substances
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Researchers found that both micro- and nanoplastics at realistic concentrations harmed the performance of aerobic granular sludge, a technology used for wastewater treatment, by reducing its ability to remove nitrogen. The plastic particles interacted with the sticky substances that hold the sludge granules together, weakening their structural integrity. The study reveals a specific mechanism by which plastic pollution can undermine wastewater treatment systems that communities rely on for clean water.
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