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Distinct responses of Pseudomonas aeruginosa PAO1 exposed to different levels of polystyrene nanoplastics
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Researchers examined the molecular mechanisms by which polystyrene nanoplastics affect Pseudomonas aeruginosa, finding dose-dependent responses in growth, metabolism, and virulence gene expression that reveal how nanoplastics interact with environmentally relevant bacteria.
Large amounts of discarded plastics in the environment can be aged into microplastics and nanoplastics, which are not easily removed, posing potential nonnegligible risks to the ecosystem and human health. Although previous studies have revealed that nanoplastics have detrimental impacts on microorganisms, the potential molecular mechanisms of nanoplastic particles' effect on microbial growth and metabolism are still lacking. Here, multiple responses of Pseudomonas aeruginosa PAO1 (PAO1) to different levels of polystyrene nanoplastics (PS NPs) exposure were investigated by physiological experiments, live/dead staining, redox status, and genome-wide RNA sequencing. The results showed that PS NPs had dual effects on PAO1, and different concentrations of PS NPs demonstrated different effects on the growth and metabolism of PAO1. All levels of PS NPs had no obvious biocidal effect on PAO1. The production and consumption of ROS were in dynamic equilibrium and could be regulated genetically to ensure that the ROS level was in the biotolerable range. 20 and 50 mg/L of PS NPs severely inhibited the nitrate reduction, while 0.1 mg/L of PS NPs promoted the denitrification and TCA cycle. Meanwhile, 20 and 50 mg/L of PS NPs resulted in intense down-regulation of genes involved in denitrification. In contrast, the expression of genes involved in respiration is promoted with generated energy to withstand stress from high-level PS NPs, coinciding with the physiological results. In addition, our results showed that PS NPs concentrations of 20 and 50 mg/L exposure substantially up-regulated the expression of genes encoding for flagellar biosynthesis and biofilm formation to tackle the stress. Our findings would provide new insights into the interactions between environmental bacteria and PS NPs at the transcriptional level, thereby enhancing our understanding of the potential risks of PS NPs to microbial ecosystems and public health.
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Researchers examined how polystyrene nanoplastics affect Salmonella enterica, a major foodborne pathogen, across a range of concentrations. They found that nanoplastics induced oxidative stress, membrane damage, and increased biofilm formation, while also triggering early activation of virulence and stress-response genes. The study suggests that nanoplastic pollution in the environment could alter bacterial survival strategies and potentially influence food safety risks.
Polystyrene nanoparticles induce biofilm formation in Pseudomonas aeruginosa
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Researchers found that polystyrene nanoparticles caused the common bacterium Pseudomonas aeruginosa to form thicker biofilms and become more resistant to antibiotics. The nanoplastics damaged bacterial cell membranes and triggered a stress response, prompting the bacteria to produce more protective biofilm as a defense mechanism. This is concerning for human health because it suggests nanoplastic pollution could make disease-causing bacteria harder to treat with existing antibiotics.
Effects of unmodified and amine-functionalized polystyrene nanoplastics on nitrogen removal by Pseudomonas stutzeri: strain characteristics, extracellular polymers, and transcriptomics
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Researchers investigated how two types of polystyrene nanoplastics — plain and amine-modified — affect the ability of bacteria to remove nitrogen from water, a process important for wastewater treatment. The amine-coated nanoplastics were found to be more disruptive than unmodified ones, altering the bacteria's cell surface, extracellular proteins, and gene expression. This matters because nanoplastics entering wastewater systems could undermine the biological processes that keep treated water safe to release into the environment.
Interactions between bacteria and nano (micro)-sized polystyrene particles by bacterial responses and microscopy
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Researchers studied how bacteria interact with polystyrene particles ranging from 60 to 2,260 nanometers and found that the smallest particles entered bacterial cells while larger ones accumulated on surfaces. The 1,040-nanometer particles, similar in size to the bacteria themselves, inhibited growth most strongly, and bacteria responded by forming biofilm complexes around the microplastics.
Impact of polystyrene nanoplastics on primary sludge fermentation under acidic and alkaline conditions: Significance of antibiotic resistance genes
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Researchers studied how polystyrene nanoplastics affect the fermentation of sewage sludge at different pH levels. They found that low doses stimulated hydrogen gas production while higher concentrations suppressed it, and that nanoplastic exposure promoted the spread of antibiotic resistance genes in the microbial community. The findings raise concerns about nanoplastics in wastewater systems potentially contributing to the broader problem of antibiotic resistance.
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