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10 páginas.- 4 figuras.- 4 tablas.- 45 referencias.- The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.est.2c03149, Recent research has demonstrated that chemotactic bacteria can disperse inside microsized pores while traveling toward favorable conditions. Microbe–microbe cotransport might enable nonmotile bacteria to be carried with motile partners to enhance their dispersion and reduce their deposition in porous systems. The aim of this study was to demonstrate the enhancement in the dispersion of nonmotile bacteria (Mycobacterium gilvum VM552, a polycyclic aromatic hydrocarbon-degrader, and Sphingobium sp. D4, a hexachlorocyclohexane-degrader, through micrometer-sized pores near the exclusion-cell-size limit, in the presence of motile Pseudomonas putida G7 cells. For this purpose, we used bioreactors equipped with two chambers that were separated with membrane filters with 3, 5, and 12 μm pore sizes and capillary polydimethylsiloxane (PDMS) microarrays (20 μm × 35 μm × 2.2 mm). The cotransport of nonmotile bacteria occurred exclusively in the presence of a chemoattractant concentration gradient, and therefore, a directed flow of motile cells. This cotransport was more intense in the presence of larger pores (12 μm) and strong chemoeffectors (γ-aminobutyric acid). The mechanism that governed cotransport at the cell scale involved mechanical pushing and hydrodynamic interactions. Chemotaxis-mediated cotransport of bacterial degraders and its implications in pore accessibility opens new avenues for the enhancement of bacterial dispersion in porous media and the biodegradation of heterogeneously contaminated scenarios., This research was funded by European Union's Horizon 2020 research and innovation program under the Marie Sklodowska- Curie grant agreement no. 895340 (BIOTAC project) and by the Spanish Ministry of Science and Innovation (PID2019- 109700RB-C21) .

The COVID-19 pandemic has caused significant increase in the production, usage, and disposal of single-use face masks. It is estimated that more than 1.5 trillion single-use face masks are used per year. While these face masks have played an important role to curb the spread of the coronavirus, their indiscriminate disposal in the environment is becoming a cause for concern. Several studies have shown that the masks can release millions of microplastics and nanoplastics, as well as other harmful chemicals when exposed to environmental conditions. However, the knowledge on the impacts of the released microplastics and chemicals to aquatic organisms is still limited. This study investigates both the acute and chronic impacts of the microplastics and chemicals on Daphnia magna. The test material was obtained via a simulated laboratory weathering experiment, and divided into three groups (microplastics alone, chemicals alone and mixture of microplastics and chemicals). The acute tests were conducted over a 48-h period on three different life stages of Daphnia magna (neonates, juveniles, and adults) while the chronic tests were conducted on neonates over a 21-day period. Chemicals alone and mixture of chemicals and microplastics decreased the survival rate of neonates and juveniles. However, microplastics alone had no effects on the survival of the neonates and the chemicals alone had no impacts on the adults. Also, chemicals alone and mixture of chemicals and microplastics significantly decreased survival during 21-day chronic exposure while microplastics alone caused significant sublethal impacts on growth, reproduction, heartbeat rate and swimming behavior. The released chemicals were analyzed using LC-MS and ICP-MS to understand how the chemical composition impacts the observed toxicity. This study shows that the released plastics and chemicals may have different impacts on Daphnia, depending on the type of tests and life stages of Daphnia tested Also see: https://micro2022.sciencesconf.org/427153/document, In MICRO 2022, Online Atlas Edition: Plastic Pollution from MACRO to nano