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The humic acid-like substances released from Microcystis aeruginosa contribute to defending against smaller-sized microplastics
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Researchers studied how the cyanobacterium Microcystis aeruginosa responds to polystyrene microplastic exposure over 17 days at different particle sizes and concentrations. They found that the algae released humic acid-like substances as part of their extracellular secretions, which helped defend against smaller microplastic particles. The study suggests that algae have adaptive mechanisms to cope with microplastic stress, but these defense responses vary depending on particle size.
Microplastics (MPs) are ubiquitous in freshwater ecosystems, but knowledge of their effects on extracellular polymeric substance (EPS) produced by algae is poorly understood. The components in specific EPS fractions of Microcystis respond when exposed to MPs is also still unclear. In this study, the responses of Microcystis aeruginosa under polystyrene (PS) microplastic exposure were studied over 17 days of cultivation, using 0.1 μm and 1.0 μm sized PS at three concentration gradients (1, 10 and 100 mg/L). Results indicate that algal growth significantly increased using the 0.1 and 1.0 μm PS at a high concentration (100 mg/L) on day 17, with growth rates of 74.71% ± 0.94% and 35.87% ± 1.23%, respectively. All tested PS had a maximum inhibitory effect on the photosynthesis on day 5, but the inhibition of photosynthetic activity by 0.1 μm PS alleviated after 13 days of exposure, indicating recovery of microalgae from the toxic environment. The two PS sizes at 100 mg/L concentration triggered EPS release in the latter stage of the experiment; meanwhile, fluorescence EEM analysis showed that smaller-sized PS (0.1 μm) at various doses noticeably increased humic acid-like substances in tightly bound EPS (TB-EPS) fractions on day 17. Our findings showed that EPS release and humic acid-like substances secretion of Microcystis likely can resist MPs exposure. The results provide new insights into the toxicity mechanism of MPs on freshwater microalgae, as well as understanding the ecological risks of microplastics.
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Researchers examined how the cyanobacterium Microcystis aeruginosa responds to different sizes of polystyrene microplastics by producing extracellular polymeric substances. They found that the composition of these protective substances varied depending on particle size, with each size triggering distinct defense mechanisms in the algae. The study reveals that extracellular polymeric substances play a crucial role in mitigating the adverse effects of microplastics on algal growth and photosynthesis.
Microcystis aeruginosa copes with toxic effects of micro/nano-plastics with varying particle sizes through different self-regulatory mechanisms
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Researchers exposed the freshwater cyanobacterium Microcystis aeruginosa to polystyrene particles of three different sizes ranging from nanoscale to microscale. All particle sizes harmed the algae, but they triggered different cellular defense mechanisms depending on their size, with nanoparticles causing the most severe damage. The findings reveal that particle size is a key factor in determining how microplastics affect aquatic microorganisms.
Size-dependent mitigation by humic acid: rescuing metabolic homeostasis from nano-plastics but not micro-plastics in Microcystis aeruginosa
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Tiny plastic particles polluting our lakes and rivers don't act alone—natural organic matter in water (like decomposed leaves and soil, called humic acid) changes how toxic they are to algae, the base of the aquatic food chain. This study found that humic acid actually helped algae recover from damage caused by nano-sized plastic particles, but didn't offer the same protection against larger microplastic particles, suggesting that plastic pollution's real-world impact depends heavily on both particle size and what else is in the water. Since these algae are a foundation of freshwater ecosystems—and can end up in the water and food we consume—underst
Effects of polystyrene microplastics on growth, physiological traits of Microcystis aeruginosa and microcystin production and release
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Researchers examined how polystyrene microplastics of various sizes affect the growth and toxin production of the harmful algae Microcystis aeruginosa. They found that microplastics inhibited algal growth at low densities, with the smallest particles causing the greatest inhibition, and also disrupted the algae's antioxidant defense system. Notably, microplastic exposure led to a significant increase in the production of the toxin microcystin-LR, raising concerns about how microplastic pollution could worsen harmful algal blooms.
Microplastic Impacts on Microalgae Growth: Effects of Size and Humic Acid
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Researchers investigated how different sizes of polystyrene microplastics affect the growth of freshwater microalgae, both with and without naturally occurring humic acid. They found that larger particles blocked light and disrupted photosynthesis, while smaller ones damaged cell walls by adhering to the algae surface. Adding humic acid significantly reduced the toxicity of smaller microplastics by forming a protective coating around the particles.
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