Seung-Woo Lee

Microplastic pollution is increasingly recognized as a potential environmental stressor for microorganisms. This study aimed to explore how surface-functionalized polystyrene (PS) microplastics influence selected cellular-level responses in two Gram-negative bacteria, Escherichia coli and Acinetobacter sp., focusing on growth, viability, biofilm formation, and membrane-associated stress. Bacterial cultures were exposed to PS microplastics with three surface chemistries: non-functionalized PS, aminated PS (PS-NH2), and carboxylated PS (PS-COOH). Exposure to PS microplastic induced species- and surface chemistry-dependent alterations in bacterial responses. Compared to the control, non-functionalized PS reduced E. coli growth and viability to 74.8% and 61.3%, respectively, while Acinetobacter sp. showed reductions to 72.1% and 69.3% following PS exposure. Biofilm formation increased significantly to 143.2% in E. coli with PS, and to 207.2% and 190.7% in Acinetobacter sp. with PS and PS–COOH, respectively. Cytotoxicity assays revealed distinct stress patterns: in E. coli, PS exposure elevated MDA and LDH levels to 155.3% and 120.5% of control levels, respectively, while ROS levels remained near baseline (100.2%), indicating predominant membrane rupture and lipid peroxidation. In contrast, Acinetobacter sp. exhibited markedly elevated ROS (118.5% and 123.5%) and MDA (190.7% and 212.8%) levels upon exposure to PS and PS–COOH, while LDH remained comparable to the control, suggesting sublethal oxidative stress and membrane perturbation. These findings demonstrate that even chemically inert PS microplastics can trigger biologically significant responses in bacteria through surface-mediated mechanisms. The observed interspecies and inter-surface variability underscores the complexity of microplastic–microbe interactions and highlights the need for microbial-level assessments in evaluating the ecological risks of microplastic pollution.

So Yoon Kim, Shinyoung Woo, Seung-Woo Lee, Eui-Man Jung, and Eun-Hee Lee . J. Microbiol. Biotechnol. 2025;35:1-10. https://doi.org/10.4014/jmb.2410.10023

Enterococci are common indicators of fecal contamination, and are used to assess the quality of fresh and marine waters, sand, soil, and sediments. However, samples collected from these environments also contain various cells and other factors that can interfere with the assays used to detect enterococci. We developed a novel assay for the sensitive and specific detection of enterococci that is resistant to interference by other cells and environmental factors. Our interference-resistant assay used 30-nm gold-nanoparticles (AuNPs), streptavidin, and a biotinylated Enterococcus antibody. Enterococci inhibited the interaction between streptavidin and biotin and led to the disaggregation of AuNPs, the absence of enterococci led to the aggregation of AuNPs, and this difference was easily detected by spectrophotometry. This interference-resistant AuNP assay was able to detect whole cells of Enterococcus in the range of 10 to 107 CFU/mL within 3 h, had high specificity for enterococci, and was unaffected by the presence of other intestinal bacteria, such as Escherichia coli. Our examination of actual samples of fresh and marine waters demonstrated no interference by other cells or environmental factors. The interference-resistance AuNP assay described here has potential for use as a rapid, simple, and effective method for monitoring enterococci in diverse environments.

Powdered activated carbon (PAC) has been extensively used as an effective adsorbent. Despite its excellent adsorption ability, PAC has drawbacks, including difficulty in filtration and reactivation after use, limitations of mass transfer in deeper areas because of its aggregated powder form, and limited applicability in high-flow systems. To overcome these limitations, we used a three-dimensional (3D) printing system to fabricate PAC into a 3D structure. Spectral and microscopic analyses indicated that PAC was embedded into 3D monolith and exhibited high porosity suitable for facile mass transfer. The designed 3D filter effectively removed 200 ppm-methylene blue (MB) within 8 h and showed an adsorption efficiency of 93.4 ± 0.9%. The adsorption of MB onto the 3D filter was described by the pseudo-first-order kinetic and Freundlich isotherm models. The negatively charged 3D filter might attract the positively charged MB, thus favoring the physical adsorption of MB onto the 3D filter. The adsorption performance of the 3D filter was tested at various pH levels of 4–10 and against MB spiked in seawaters and freshwaters to evaluate its feasibility for use in real environments. Finally, the reproducibility and reusability of the 3D filter were demonstrated through repeated adsorption and desorption processes against MB.