Impact of different organic matters on the occurrence of antibiotic resistance genes in activated sludge

The occurrence of antibiotic resistance genes (ARGs) in various environments has drawn worldwide attentionduetotheirpotentialrisks.Previousstudieshavereportedthatava-rietyofsubstancescanenhancetheoccurrenceanddisseminationofARGs.However,fewstudieshavecomparedtheresponseofARGsunderthestressofdifferentorganicmattersinbiologicalwastewatertreatmentsystems.Inthisstudy,sevenorganicpollutantswereaddedintowastewatertreatmentbioreactorstoinvestigatetheirimpactsontheARGoccurrenceinactivatedsludge.Basedonhigh-throughputsequencing,itwasfoundthatthemicrobialcommunitiesandARGpatternsweresignificantlychangedintheactivatedsludgeexposedtotheseorganicpollutants.Comparedwiththenon-antibioticrefractoryorganicmatters,antibioticsnotonlyincreasedtheabundanceofARGsbutalsosignificantlychangedtheARGcompositions.TheincreaseofGram-negativebacteria(e.g.,Archangium,ProsthecobacterandDokdonella)carryingARGscouldbethemaincauseofARGproliferation.Inaddition,sig-nificantco-occurrencerelationshipsbetweenARGsandmobilegeneticelementswerealsoobservedinthesludgesamples,whichmayalsoaffecttheARGdiversityandabundanceduringtheorganicmattertreatmentinthebioreactors.Overall,thesefindingsprovidenewinformationforbetterunderstandingtheARGoccurrenceanddisseminationcausedbyor-ganicpollutantsinwastewatertreatmentsystems.(c) 2022 The ResearchCenterforEco-EnvironmentalSciences,ChineseAcademyofSciences.PublishedbyElsevierB.V.IntroductionTheantibioticresistancegenes(ARGs)andantibioticresis-tantbacteria(ARB)innaturalandengineeringenvironmentshavedrawnworldwideattentionsduetotheirpotentialriskstohumansandanimals.WithanincreasingnumberofARGsfoundinvariousenvironments,theyhavebeenregardedas*Correspondingauthor.E-mail:linye@nju.edu.cn(L.Ye).akindofnewpollutants,especiallyinthewaterenviron-ment(Prudenetal.,2006;Zhangetal.,2009).Wastewaterfromvarioussourcesandmicroorganismsfromdifferentenviron-mentscontinuouslyenterthewastewatertreatmentplants,whilethetreatmentprocesseshavelimitedeffectsoninacti-vationofARBandARGsandmayevenpromotetheirprolifer-ation(Michaeletal.,2013).Therefore,thebiologicalreactorsinwastewatertreatmentplantsareregardedasthehotspotsofARGoccurrenceanddissemination(Karkmanetal.,2018).AsfortheoccurrenceofhighabundanceofARGsinvariousenvironments,oneofthemostdirectandimportantcausesishttps://doi.org/10.1016/j.jes.2022.04.0211001-0742/(c) 2022 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Automated summary

This study investigated the impact of adding different organic pollutants on the occurrence of antibiotic resistance genes (ARGs) in activated sludge. The results showed that antibiotics not only increased the abundance of ARGs, but also significantly changed their compositions. Gram-negative bacteria were found to be the main carriers of ARGs, and significant co-occurrence relationships between ARGs and mobile genetic elements were observed in the sludge samples.