Short-term exposure to benzalkonium chloride in bacteria from activated sludge alters the community diversity and the antibiotic resistance profile

The continuous introduction of cleaning products containing benzalkonium chloride (BAC) from household discharges can mold the microbial communities in wastewater treatment plants (WWTPs) in a way still poorly understood. In this study, we performed an in vitro exposure of activated sludge from a WWTP in Costa Rica to BAC, quantified the changes in intI1, sul2, and qacE/qacEΔ1 gene profiles, and determined alterations in the bacterial community composition. The analysis of the qPCR data revealed elevated charges of antibiotic resistance genes in the microbial community; after BAC’s exposure, a significant increase in the qacE/qacEΔ1 gene, which is related to ammonium quaternary resistance, was observed. The 16S rRNA gene sequences’ analysis showed pronounced variations in the structure of the bacterial communities, including reduction of the alpha diversity values and an increase of the relative abundance of Alphaproteobacteria, particularly of Rhodospseudomonas and Rhodobacter. We confirmed that the microbial communities presented high resilience to BAC at the mg/mL concentration, probably due to constant exposure to this pollutant. They also presented antibiotic resistance-related genes with similar mechanisms to tolerate this substance. These mechanisms should be explored more thoroughly, especially in the context of high use of disinfectant.Universidad de Costa Rica/[]/UCR/Costa RicaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto de Investigaciones en Salud (INISA)UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigaciones en Productos Naturales (CIPRONA)UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Centro de Investigación en Enfermedades Tropicales (CIET)UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Acute toxicity and cholinesterase inhibition of the nematicide ethoprophos in larvae of gar Atractosteus tropicus(Semionotiformes: Lepisosteidae).

Biomarkers are a widely applied approach in environmental studies. Analyses of cholinesterase (ChE), glutathione S-transferase (GST) and lipid peroxidation (LPO) are biomarkers that can provide information regarding early effects of pollutants at different biochemical levels on an organism. The aim of this study was to evaluate the biomarker approach on a Costa Rican native and relevant species. For this, larvae of gar (Atractosteus tropicus) were exposed to the organophosphorus nematicide, ethoprophos. Acute (96hr) exposure was conducted with pesticide concentrations ranging from 0.1µg/L to 1 500µg/L. The 96hr LC50 calculated was 859.7µg/L. After exposure, three biomarkers (ChE, GST and LPO) were analyzed in fish that survived the acute test. The lowest observed effect concentration (LOEC) regarding ChE activity inhibition was 50µg/L. This concentration produced a significant inhibition (p<0.05) of the enzyme by 20%. The highest concentration tested without showing any effect on ChE activity and therefore considered as no observed effect concentration (NOEC) was 10µg/L. Ethoprophos concentration of 400µg/L caused a ChE inhibition by 79%. In this study, no significant variations (p>0.05) in GST activity and LPO were observed in A. tropicus larvae after exposure to ethoprophos.El proceso de reproducción inducida de Atractosteus tropicus es útil para la acuicultura y la reintroducción en zonas donde las poblaciones silvestres se han reducido considerablemente. En larvas de esta especie se evaluó la toxicidad aguda, así como la respuesta de tres biomarcadores: actividad colinesterasa (ChE), actividad de Glutation S-transferasa (GST) y peroxidación de lípidos (LPO). Asimismo, se realizaron exposiciones agudas (96hr) a etoprofos (nematicida organofosforado), en donde se utilizaron concentraciones entre 0.1µg/L y 1 500µg/L del nematicida. La concentración letal 50 (LC50) calculada fue de 859.7µg/L; la máxima concentración sin efecto en los organismos (NOEC) 10µg/L y la concentración más baja en la cual se observó algún efecto (LOEC) 50µg/L. A esa concentración, el efecto observado fue una reducción significativa (p<0.05) en la actividad de la ChE. Una concetración de etoprofos de 400µg/L causó una inhibición del 79% en la actividad ChE. La actividad GST y la LPO no mostraron una respuesta significativa (p>0.05) luego de la exposición de los organismos a etoprofos

Acute toxicity and cholinesterase inhibition of the nematicide ethoprophos in larvae of gar Atractosteus tropicus (Semionotiformes: Lepisosteidae)

Biomarkers are a widely applied approach in environmental studies. Analyses of cholinesterase (ChE), glutathione S-transferase (GST) and lipid peroxidation (LPO) are biomarkers that can provide information regarding early effects of pollutants at different biochemical levels on an organism. The aim of this study was to evaluate the biomarker approach on a Costa Rican native and relevant species. For this, larvae of gar (Atractosteus tropicus) were exposed to the organophosphorus nematicide, ethoprophos. Acute (96hr) exposure was conducted with pesticide concentrations ranging from 0.1&#956;g/L to 1 500&#956;g/L. The 96hr LC50 calculated was 859.7&#956;g/L. After exposure, three biomarkers (ChE, GST and LPO) were analyzed in fish that survived the acute test. The lowest observed effect concentration (LOEC) regarding ChE activity inhibition was 50&#956;g/L. This concentration produced a significant inhibition (p<0.05) of the enzyme by 20%. The highest concentration tested without showing any effect on ChE activity and therefore considered as no observed effect concentration (NOEC) was 10&#956;g/L. Ethoprophos concentration of 400&#956;g/L caused a ChE inhibition by 79%. In this study, no significant variations (p>0.05) in GST activity and LPO were observed in A. tropicus larvae after exposure to ethoprophos.<br>El proceso de reproducción inducida de Atractosteus tropicus es útil para la acuicultura y la reintroducción en zonas donde las poblaciones silvestres se han reducido considerablemente. En larvas de esta especie se evaluó la toxicidad aguda, así como la respuesta de tres biomarcadores: actividad colinesterasa (ChE), actividad de Glutation S-transferasa (GST) y peroxidación de lípidos (LPO). Asimismo, se realizaron exposiciones agudas (96hr) a etoprofos (nematicida organofosforado), en donde se utilizaron concentraciones entre 0.1&#956;g/L y 1 500&#956;g/L del nematicida. La concentración letal 50 (LC50) calculada fue de 859.7&#956;g/L; la máxima concentración sin efecto en los organismos (NOEC) 10&#956;g/L y la concentración más baja en la cual se observó algún efecto (LOEC) 50&#956;g/L. A esa concentración, el efecto observado fue una reducción significativa (p<0.05) en la actividad de la ChE. Una concetración de etoprofos de 400&#956;g/L causó una inhibición del 79% en la actividad ChE. La actividad GST y la LPO no mostraron una respuesta significativa (p>0.05) luego de la exposición de los organismos a etoprofos