The‘insurancehypothesis’statesthatbiodiversityinsuresecosystemsagainstdecreasesintheirfunctionalityandisapplicabletomostnaturalecosystems.Inthegut,thishypothesisimpliesthattherichdiversityoftheintestinalmicrobiota(thecommunityofmicroorganismsthatresideinthegut)iscrucialandprotectiveforsustainingamicrobialequilibrium(astablecompositionofspeciesinthemicrobiota)andfortheintegrityofthemucosalbarrier1–4.Thiscomplexecosystemofintestinalbacterialcommunitiesischaracterizedbyacapacityforself-regeneration,whichisalsoknownastheresiliencephenomenon.Thus,theintestinalmicrobiotahastheabilitytorestoreitsequilibriumafteranexternalperturbation,suchasinfectionwithapathogenorantibiotictreatment.Thetheoreticalconceptofresilience(BOX1),whichisgenerallydescribedasthecapacityofanecosystemtorecoverfromamodulatingperturbation,comprisesInthisOpinionarticle,wefocusontheinteractionsbetweenbacteria,thehostandtheenvironmentthatenablemicrobialresilienceagainstdietary,antibioticorbacteriotherapy-inducedperturbations,andtheimplicationsofmicrobialresilienceforhumanhealth.Webrieflyconsiderresilienceinhealthanddiseasebeforeintroducingtheecologicalconceptsthatexplainresilienceofthemicrobiotaandconsiderthemechanismsthatcontributetothis.Last,weproposehowresiliencemayaffectthemicrobiotaduringdevelopment,antibiotictreatmentandbacteriotherapy.ConceptsofmicrobialresilienceThemicrobialcommunitiesthatresideinthehumangutareconstantlyexposedtoenvironmentalperturbations.Throughouthumanevolution,theintestinalmicrobiotahasbeenchallengedbynutrientintakefromdiverseenergysourcesandconstantexposuretonewbacteria,fungi,protozoaandviruses.Inthepast50years,societalandculturalchangeshaveaddedexposuretoantibioticsandtheconstituentsofprocessedfoodsandhygieneproducts(forexample,emulsifiersandartificialsweeteners)asnovelperturbationsofmicrobialecology,whichhavespreadwiththeglobalizationoftheWesternindustrializedlifestyle9,10.Complexecosystems,suchasthemicrobialcommunitiesinthegut,arethoughttobeabletoattainalimitednumberof...
