Archaea diversity in vegetation gradients from the Brazilian Cerrado

(1)

h ttp : / / w w w . b j m i c r o b i o l . c o m . b r /

Short

communication

Archaea

diversity

in

vegetation

gradients

from

the

Brazilian

Cerrado

Ademir

Sergio

Ferreira

de

Araujo

a,∗

_,

_Lucas

_Wiliam

_Mendes

b

_,

_Walderly

_Melgac¸o

_Bezerra

c

_,

Luis

Alfredo

Pinheiro

Leal

Nunes

a

_,

_Maria

_do

_Carmo

_Catanho

_Pereira

_de

_Lyra

d

_,

Marcia

do

Vale

Barreto

Figueiredo

d

_,

_Vania

_Maria

_Maciel

_Melo

c a_Federal_University_of_Piauí,_Agricultural_Science_Center,_Soil_Quality_Lab.,_Teresina,_PI,_Brazil

b_University_of_Sao_Paulo_USP,_Center_for_Nuclear_Energy_in_Agriculture_CENA,_Cell_and_Molecular_Biology_Laboratory,_Piracicaba,_SP, Brazil

c_Federal_University_of_Ceara,_Laboratório_de_Ecologia_Microbiana_e_{Biotecnologia,}_Fortaleza,_CE,_Brazil d_Agronomic_Institute_of_Pernambuco,_Recife,_PE,_Brazil

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received2March2017

Accepted25August2017

Availableonline11February2018

AssociateEditor:ValeriaOliveira

Keywords: Microbialecology Soilmicrobiology 16SrRNA Tropicalsoils

a

b

s

t

r

a

c

t

Weused16SrRNAsequencingtoassessthearchaealcommunitiesacrossa gradientof

Cerrado.Thearchaealcommunitiesdiffered acrossthegradient.Crenarcheotawasthe

mostabundantphyla,withNitrosphaeralesandNRPJasthepredominantclasses.

Eury-achaeotawasalsofoundacrosstheCerradogradient,includingtheclassesMetanocellales

andMethanomassiliicoccaceae.

anopenaccessarticleundertheCCBY-NC-NDlicense(http://creativecommons.org/

licenses/by-nc-nd/4.0/).

SoilmicroorganismsconstituteathirdoftheEarth’sbiomass,

playingimportantecologicalandbiogeochemicalrolesin

ter-restrialecology.Amongthemicroorganismsthatinhabitsoils,

the domainArchaea isparticularlyimportantbecause it is

abundant and plays important roles in C and N cycling.1

Thisdomain constitutes oneofthe threemajor

evolution-ary lineages of life on Earth, and although it has long

beenbelievedthattheseorganismsmainlyinhabitextreme

∗ _{Corresponding}_author_at:_Soil_Quality_Lab.,_Agricultural_Science_Center,_Federal_University_of_Piauí,_Teresina,_PI,_Brazil.

E-mail:asfaruaj@yahoo.com.br(A.S.Araujo).

environments, previousstudiesdemonstrated thattheyare

widely distributed around the world in different types of

soils.2,3

Sincetherecognitionofthearchaealdomaininthetree

oflife,4_studies_have_been_focused_to_explore_their_presence

and function in a wide range of environments. With the

advance ofDNA-based molecular toolsand genomic

anal-ysis, the knowledge of this domain has evolved and the

https://doi.org/10.1016/j.bjm.2017.08.010

(2)

Table1–VegetationdiversityindicesintheCerradoareas.19

Campograminoide Cerradostrictosensu Cerradao Florestadecidual

Plantrichnesse _4.7 ₁₁ ₁₇ ₁₈

Plantdiversityf _0.2 _0.85 _1.10 _1.11

Plantdensityg _4.7 _27.1 _35.0 _51.8

Vegetationh a b c d

a _Andropogon_fastigiatus;_Aristida_longifolia;_Eragrostis_maypurensis.

b _Andropogon_fastigiatus;_Aristida_longifolia;_Terminalia_fagifolia;_Magonia_pubescens;_Hymenaea_courbaril;_Plathymenia_reticulata;_Qualea_{grandiﬂora;}

Combretummelliﬂuum;Lippiaoriganoides;Anacardiumoccidentale;Simaroubaversicolor;Vataireamacrocarpa.

c _Aspidosperma_discolor;_Parkia_{platycephala;}_Terminalia_fagifolia;_Piptadenia_{moniliformis;}_Plathymenia_reticulata;_Qualea_parviﬂora;_Anacardium

occiden-tale;Copaiferacoriacea;Thiloaglaucocarpa;Caseariagrandiﬂora.

d _Aspidosperma_{multiﬂorum;}_Aspidosperma_subincanum;_Campomanesia_aromática;_Casearia_lasiophylla;_Casearia_ulmifolia;_Copaifera_coriacea;

Ephedran-thuspisocarpus;Piptadeniamoniliformis;Pterocarpusviolaceus;Thiloagalucocarpa.

e _Species/100_m2_. f _H/100_m2_. g _{Individual/100}_m2_. h _Species_of_plants_present.

current archaealclassiﬁcation israpidly moving. Presently,

20 archaeal phyla are recognized by small subunit RNA

databases;however,ithasbeenreportedthat14phylahave

no cultured representative.5 _Most _of _culturable _members

of Archaea belong to the two main phyla Euryarchaeota

and Crenarchaeota. Other new phyla have been proposed

inthelast years,forexample Nanoarchaeota,basedonthe

isolation of a hypertehermophilic symbiont Nanoarchaeum

equitans6_and_{Thaumarchaeota.}7_Most_recently,_two

superphy-lum havebeen proposed, namely(i) TACK, which includes

thephylaThaumarchaeota,Aigarchaeota,Crenarchaeotaand

Korarchaeota,8 _and _(ii) _Asgard, _which _consist _in _a _sister

group to TACK and are considered more closely related

to the original eukaryote.9 _Together _with _the _advance _of

Archaea classiﬁcation, their functional role in the

ecosys-temhasalsobeenthe focus ofrecentstudies.Members of

Archaeacarryoutmanystepsinthenitrogencycle,suchas

nitrate-basedrespirationanddenitriﬁcation.10_Communities

ofautotrophicand heterotrophicArchaeacatalyzeironand

sulfuroxidation,whichinﬂuencethereleaserateofmetals

andsulfurtotheenvironment.11 _Also,_regarding_the_carbon

cycle,allknownmethanogenorganismsbelongexclusivelyto

Archaeadomainandaregenerallyfoundinoxygen-depleted

environments.12

InBrazil,studiesregardingthediversityofArchaeahave

beenconductedforsomeimportantecosystems,suchas

Ama-zonianand Atlanticforests,13,14 _as_well_as _in_mangroves.15

InthecaseoftheBrazilianCerrado,previousstudies

investi-gatedthediversityofarchaeainsoilsfromtheCentralPlateau

andfoundthatCrenarcheotawasthemostabundantarchaeal

groupintheecosystem.3,16_However,_it_has_been_hypothesized

thatthevegetationandsoilconditionsintheCerradofrom

NortheasternBrazildiffersfromthoseoftheCentralPlateau.17

Therefore, the pattern of Archaea communities would be

different because the vegetation and soil conditions drive

soilmicroorganisms.Previousstudieshaveshowndifferences

betweenbacterialdiversityinthesoilsobtainedfromCerrado

intheNortheastwhencomparedtothosefromtheCentral

Plateau.18_Therefore,_we_used_{next-generation}_sequencing_of

the 16S rRNA gene insoil samples from vegetation

gradi-entsobtainedfromCampograminoide,Cerradostrictosensu,

CerradaoandFlorestadecidualtounderstandthediversityof

ArchaeainthesoilsofCerradoinNortheasternBrazil.

The study was conductedin a preserved Brazilian

Cer-rado within SeteCidades National Park(PNSC) (04◦02-08S

and41◦40-45W),Northeast,Brazil.Thisregionpresentstwo

distinctseasons(wetanddry)withanannualaverage

temper-atureat25◦Candrainfallof1558mmdistributedinFebruary

throughApril.Weevaluatedfourdifferentareas(with1000m2

each one) inagradientofvegetation(‘Campograminoide’,

‘Cerrado stricto sensu’, ‘Cerradao’ and ‘Floresta decidual’)

(Table1;Fig.1).

Each area was separated inthree transects(replication)

wheresoilsampleswerecollectedattopsoillayer(0–20cm

depth;threepointspertransect)inMarch(wetseason),2014.

Allsoilsampleswereimmediatelystoredinsealedplasticbags

andtransportedinaniceboxtothelaboratory.Aportionofthe

soilsampleswasstoredinbagsandkeptat−20◦CforDNA

analysisandanotherportionwasair-dried,sievedthrougha

2-mmscreenandhomogenizedforchemicalanalysesusing

standardlaboratoryprotocols.20

Soil DNA was extracted from 0.5g (total humidweight)

of soil using the PowerLyzer PowerSoil DNA Isolation Kit

(MoBIO Laboratories, Carlsbad, CA, USA), according to the

manufacturer’sinstructions.ThequalityoftheextractedDNA

wascheckedwiththeNanodropND-1000spectrophotometer

(ThermoScientiﬁc,Waltham, MA,USA),and itwas

quanti-ﬁedbyQubit® 2.0ﬂuorometerusingthedsDNABRAssaykit

(InvitrogenTM_)._The_integrity_of_the_DNA_was_also_conﬁrmed_by

electrophoresisina0.8%agarosegelwith1×TAEbuffer.The

ampliconlibraryofthearchaeal16SrRNAgeneswere

ampli-fiedusingtheregion-specificprimers(515F/806R).21_The_first

step ampliﬁcationcomprised 25␮Lreaction containing the

following:14.8␮Lofnuclease-freewater(Certiﬁed

Nuclease-free,Promega,Madison,WI,USA),2.5␮Lof10×HighFidelity

PCRBuffer (Invitrogen,Carlsbad,CA, USA),1.0␮Lof50mM

MgSO4, 0.5␮L ofeach primer (10␮Mconcentration, 200pM

ﬁnalconcentration),1.0unitofPlatinumTaqpolymeraseHigh

Fidelity(Invitrogen,Carlsbad,CA,USA),and4.0␮Loftemplate

DNA(10ng).TheconditionsforPCRwereasfollows21_:₉₄◦_C_for

4mintodenaturetheDNA,with35cyclesat94◦Cfor45s,50◦C

(3)

Fig.1–MappresentingthegradientofCerradoatSeteCidadesNationalPark,Brazil.

at72◦C.Inthesecondstep,auniquepairofIlluminaNextera

XTindexes(Illumina,SanDiego,CA)wasaddedtobothends

oftheampliﬁedproducts.Each50␮Lreactioncontainedthe

following:23.5␮Lofnuclease-freewater(Certiﬁed

Nuclease-free,Promega,Madison,WI,USA),5.0␮Lof10×HighFidelity

PCRBuffer(Invitrogen, Carlsbad,CA,USA), 4.8␮Lof25mM

MgSO4, 1.5␮LofdNTP(10mMeach),5.0␮LofeachNextera

XTindex(Illumina,SanDiego,CA,USA),1.0unitofPlatinum

TaqpolymeraseHighFidelity(Invitrogen,Carlsbad,CA,USA),

and5.0␮LofeachproductfrompreviousPCR.Theconditions

forthissecondroundPCRwereasfollows:95◦Cfor3minto

denaturetheDNA,with8cyclesat95◦Cfor30s,55◦Cfor30s,

and72◦Cfor30min,withaﬁnalextensionof5minat72◦C.

Afterindexing,the PCRproductswerecleanedupusing

Agencourt AMPure XP – PCR puriﬁcation beads (Beckman

Coulter,Brea,CA,USA),accordingtothemanufacturer’s

man-ual,andquantiﬁedusingthedsDNABRassayKit(Invitrogen,

Carlsbad,CA, USA) on a Qubit 2.0 ﬂuorometer(Invitrogen,

Carlsbad,CA,USA).Oncequantiﬁed,differentvolumesofeach

librarywerepooledintoasingletubeinequimolar

concen-tration. After quantiﬁcation, the molarity of the pool was

determinedanddilutedto2nM,denatured,andthendiluted

toaﬁnalconcentrationof8.0pMwitha20%PhiX(Illumina,

SanDiego,CA,USA)spikeforloadingintotheIlluminaMiSeq

sequencingmachine(Illumina,SanDiego,CA,USA).

SequencedatawereprocessedusingQIIMEfollowingthe

UPARSEstandardpipelineaccordingtoBrazilianMicrobiome

Project22 _to_produce_an_OTU_table_and _a_set _of

representa-tive sequences. Brieﬂy,the reads were truncated at240bp

and quality-ﬁlteredusing amaximum expectederrorvalue

of 0.5. Pre-ﬁltered reads were dereplicated and singletons

wereremovedandﬁlteredforadditionalchimerasusingthe

RDPgolddatabaseusingUSEARCH7.0.Thesesequenceswere

clusteredintoOTUsata97%similaritycutofffollowingthe

UPARSEpipeline.Afterclustering,thesequenceswerealigned

andtaxonomicallyclassiﬁedagainsttheGreengenesdatabase

(version13.8).23 _The_sequences_were _submitted_to_the_NCBI

SequenceReadArchiveunderthenumberSRP091586.

Redundancy Analysis (RDA) was used to determine the

correlationbetweenarchaealcommunitystructureandsoil

physicochemicalproperties.TheOTUtablewasinitially

ana-lyzed using Detrended Correspondence Analysis (DCA) to

evaluatethegradientsizeofthespeciesdistribution,which

(4)

Table2–SoilphysicochemicalpropertiesatdifferentsitesacrossthegradientofCerrado.

Site Moisture(%) Temperature(◦C) TOC(gkg−1) pH P(mgkg−1) K(cmolckg−1) CEC(cmolckg−1)

Campograminoide 7.3c ₃₂a _4.3c _4.5c _3.9c _1.4b _2.28b

Cerradostrictosensu 10.5b ₃₀b _8.3b _4.3b _3.9b _1.8b _2.31b

Cerradao 11.9b ₃₀b _9.1b _4.6b _4.5b _1.6b _2.35b

Florestadecidual 31.8a ₂₈c _15.2a _4.9a _5.3a _3.8a _4.91a

TOC,totalorganicC;CEC,cationexchangecapacity.

Valuesfollowedbythesameletterwithineachcolumnarenotsigniﬁcantlydifferentatthe5%level,asdeterminedbyStudent’st-test.

revealingthatthebest-ﬁtmodelforthedatawasRDA. For-ward selection (FS) and the Monte Carlo permutation test wereappliedwith 1000random permutationstoverify the signiﬁcance of soil chemical properties upon a microbial community.Weusedpermutationalmultivariateanalysisof variance(PERMANOVA)24 _to_test_whether_sample_categories

harbored signiﬁcantly different archaeal community

struc-ture.RDAplotsweregeneratedusingthesoftwareCanoco4.5

(Biometrics,Wageningen,TheNetherlands),andPERMANOVA

andalphadiversityindexwerecalculatedwiththesoftware

PAST.25_To_determine_the_differences_in_abundance_of_archaeal

groupsamongsoilsamples,theStatisticalAnalysisof

Metage-nomicProﬁles(STAMP)softwarepackagewasused.26_The_OTU

tablewasusedasinput,andP-valueswerecalculatedusing

thetwo-sidedWelch’st-test,27_while_conﬁdence_intervals_were

calculatedusingDPWelch’sinvertedandcorrectionwasmade

usingBenjamini–Hochbergfalsediscoveryrate.28

In this study, we examined the archaeal structure and

compositioninthesoilsfromvegetationgradientsfromthe

Cerrado.Weused16SrRNAsequencingtoassessthearchaeal

communitiesandcorrelatedthemwithsoilchemical

parame-ters.Ourresultsshowedthatsoilparametersdifferedbetween

thesamplingsites.AreasunderCampograminoide,Cerrado

strictosensuandCerradaopresentedthehighestsoil

temper-atureandthelowestN,P,K,andCECcomparedwithFloresta

decidual(Table2).Soilmoisture,pH,andTOCcontentwere

similarbetweenCerradostrictosensuandCerradao,andthey

werethelowestandhighestinCampograminoideand

Flo-restadecidual,respectively.

Thesemarkedlydifferentsoilconditions,mainlybetween

Campograminoide and Floresta decidual, exist because of

the differences in plant cover and the communities, both

ofwhichcaninﬂuencesoilproperties.Forexample,Campo

graminoide iscoveredmostly by grasses, whereas Floresta

decidual is covered by trees. RDA showed the differences

betweenthearchaealcommunitiesacrossthegradients(Fig.2)

andindicatedthattheFlorestadecidualwasthemostdistinct

comparedtotheotherareas.

Additionally,RDAshowedthatthecompositionofarchaea

communitieswasstronglycorrelatedwithspeciﬁcsoil

prop-ertiesacrosstheCerradogradients.Ourresultsshowedthat

thearchaealcommunityofFlorestadecidualcorrelatedwith

soilmoisture,TOC,CEC,P,K,andN.Ontheotherhand,soil

temperatureandpHcorrelatedwithCampograminoide,

Cer-radostrictosensuandCerradao.Theseresultsindicatethat

the archaeacommunity differs acrossthe gradients ofthe

Cerradoandisinﬂuencedbysoilconditions.BecauseCampo

graminoide,CerradostrictosensuandCerradaohadsimilar

soilconditions,theirarchaeacommunitiesweremoresimilar

1.0 -0.6 Axis 2 (9.9%) Axis 1 (16.1%) P K N CEC TOC Moisture Temperarure pH* -1.0 1.0

Fig.2–Redundancyanalysis(RDA)ofarchaealcommunity patternsandsoilcharacteristicsfromsamplesofCampo graminoide,Cerradostrictosensu,CerradaoandFloresta decidual.Arrowsindicatecorrelationbetween

environmentalparametersandarchaealproﬁle.The signiﬁcanceofthesecorrelationswereevaluatedviathe MonteCarlopermutationtestandisindicatedby*(P<0.05).

toeachother whencomparedtoFlorestadecidual.

Accord-ingtoCatãoet al.3 _the_soil_conditions_drive_the_differences

in thediversity ofArchaeain theBrazilian Cerrado. These

authorscomparedandcontrastedCerradodensoandMatade

GaleriafromtheBrazilianCerradoandfounddifferencesin

thecommunitystructuresofArchaea.Thevariedsoil

condi-tionsfoundacrossthegradientsofvegetationhaveinﬂuenced

the bacterial diversity.18 _{Interestingly,}_our _results _highlight

thesoilpHasasigniﬁcantdriverofarchaeacommunitiesin

thesesoils.AccordingtoGorres,29_soil_pH_is_the_main_driver_of

archaealcommunitystructureinsoils.Thisstrongcorrelation

betweensoilpHandthemicrobialcommunitystructuremay

bebecausepHandtheotherphysicochemicalsoilparameters

aresocloselyrelated.Mostmicroorganismshave

intracellu-larpHthatvariesintherangeofpH7±1;therefore,asmall

variationoftheenvironmentalpHcouldexpose

microorgan-ismstostress.Archaeaweredetectedinallanalyzedsamples

andshowedverylowdiversitycomparedtothebacterial

com-munityfoundinthesamesamples.18_{Interestingly,}_Floresta

decidual presented the lowest alpha diversity when

com-paredtotheother areas(Fig.3).Ithasbeensuggestedthat

anenvironmentinequilibrium,suchasforest,theecosystem

functioningismaintainedbasedonlowerlevelsofdiversity,

but high abundance of microorganisms; in contrast,

envi-ronmentsunderstresswouldpresentanincreaseddiversity,

(5)

2.5 2.0 1.5 1.0 Shannon div ersity inde x 0.5 Campo graminoide Cerrado stricto sensu Cerradao Floresta decidual a a b ab

Fig.3–DiversitymeasurementbasedonShannon’sindex ofarchaealcommunitiesinsoilsfromCampograminoide, Cerradostrictosensu,CerradaoandFlorestadecidual.

themaintenanceofessentialecosystemfunctions.30

Consid-ering thatCerrado areas are more proneto environmental

stress,suchashightemperature,lowmoistureand

oligotro-phy,thehigherarchaealdiversitywouldbeexpected.

Atotalof3078reads wereclusteredin33 OTUs

accord-ingtotheGreengenestaxonomical classiﬁcation.Wefound

Crenarchaeotatobethemostabundantphylaacrossthe

Cer-radogradients,amongwhichNitrosphaeralesandNRPJwere

thepredominantclasses(Fig.4).Organismsbelongingtothe

largely non-thermophilicCrenarchaeotaappeartobe

ubiq-uitousinsoilsystemsand aredominantover euryarchaeal

populationsingrasslandsoils.31

TheseﬁndingsagreewithpreviousstudiesintheBrazilian

Cerrado, whichhave reportedCrenarcheota asmost

domi-nantphylumandNitrosphaeralesasanimportantgroup.3,16

TherelativeabundanceofNitrosphaeralesandNRPJdiffered

across the regions. Floresta decidual showed the highest

abundanceofNitrosphaerales,whereasCampograminoide,

Cerrado stricto sensu and Cerradao showed the highest

abundanceofNRPJ.Previously,Nicolet al.32 _have_indicated

thatCrenarchaeotafromsoilsmayhavespeciﬁcassociation

with plant roots, playing an important role in the

rhi-zosphere. Nitrosphaerales are importantammonia-oxidizer

organisms,33_and_although_ammonia_oxidation_occurs_in_both

BacteriaandArchaea,thearchaealgroupdominatesinboth

soil and marine environments.34 _{Nitrogen-related}

microor-ganisms are commonlyfound abundantlyin forestsoils,30

whichmayexplainthehigherabundanceofNitrosphaerales

inourforestsamples.Also,Navarreteetal.35_showed_that_the

diversityofammonia-oxidizingarchaealcommunitiestendto

behigherinprimaryforests.Ontheotherhand,theNRPJgroup

wasmoreabundantinCerradosites.Thisgroupbelongsto

theMarineBenthicGroupA,anunculturedarchaealcluster

initiallydescribedfromcoldcontinentalslopeanddeep-sea

sediments.36 _Members _of _this _group _are _commonly _found

in oligotrophic soils, such as boreal forests,37 _which _may

explainitshigherabundanceinourCerradosamples.In

sum-mary,ourresultsshowedahighabundanceofCrenarchaeota

groupsinoursamples,withdifferentialabundancebetween

sites,suggestingthatmembersofthisgroupplaydistinctand

importantrolesinthesoilecosystem.

ThephylumEuryarchaeotaisconsideredthemost

phys-iologically diverse and includes methanogens, halophiles

and thermophile organisms. Members of this phylum

were also found across the Cerrado gradients, including

the classes Metanocellales and Methanomassiliicoccaceae.

Interestingly, the Metanocellales class was detected only

at Campo graminoide, which also had a high

abun-danceofMethanomassiliicoccaceae.Similarly,Cerradostricto

sensu showed high abundance of

Methanomassiliicoc-caceae.Thefamily Methanomassiliicoccaceae comprisesof

a methanogenic lineageof theclass Thermoplasmata,and

members ofthe Methanocellales family are methanogenic

organisms,contributingtotheglobalmethanecycle.38_In_this

sense,ourresultsshowthatimportantgroupsrelatedto

car-bon cycle areabundantinCampograminoide and Cerrado

strictosensu. Euryarchaeota :Methanomassiliicoccaceae Euryarchaeota :Methanocellales Crenarchaeota : NRPJ Crenarchaeota : Nitrosphaerales b ab a a a a a a b b b b 0.01 0.1 1 10 100

Proportion of sequences (log scale)

Campo graminoide Cerrado stricto sensu Ceradao Floresta decidual

Fig.4–AveragerelativeabundanceofthemostabundantarchaealgroupsinsoilsfromCampograminoide,Cerradostricto sensu,CerradaoandFlorestadecidualasrevealedbythe16SrRNAgeneribotyping.Foreachsampletype,thenumberof replicatesisn=9.Differentlowerlettersindicatesigniﬁcantdifference(FDR,P<0.05)amongsamples.

(6)

AsshownintheRDA,pHwasthemaindriverofthearchaea

communitiesacrossthegradients.Ithasbeendescribedthat

pHdominatesthevariationofarchaealdiversityand

commu-nitycompositionintropicalsoils.39_In_a_large-scale_study,_the

authorsshowedanichespecializationofterrestrialarchaeal

ammoniaoxidizersbasedonpH, showingthatamoA

abun-danceanddiversityincreasedwithsoilpH.40_In_our_samples,

thehighsoilpHfoundintheFlorestadecidualareafavoredthe

dominanceofNitrosphaerales,whichissensitivetolowpH.41

Ontheotherhand,ahighabundanceofEuryachaeota,

specif-icallyMetanocellales,intheCampograminoideregionmaybe

relatedtothelowsoilpHfoundinthisarea.AccordingtoHu

etal.,41_soil_pH_is_a_driver_of_{methanogenesis}_and_subsequently

maypromoteshiftsinthearchaealcommunitycomposition

fromCrenarchaeotatomethanogenicEuryarchaeota.

Inconclusion,ourdatashowedthatalthoughthemostof

detectedtaxaaresharedbetweenallfourareas,thearchaeal

structure and abundance differed across these gradients

andwasstronglydrivenbysoilphysicochemicalproperties.

The soil pH was the main driver of archaeal

communi-tiesin the studiedsoils, and this can beexplained bythe

difference between the sites, where Florestadecidual

pre-sentedhighervalueswhileCampograminoidewasmoreacid.

Resultsshowedthat Crenarcheotawas themost dominant

phylum,followedbyEuryarchaeota.Additionally,differential

soilparameters leadto distinct functional potential ofthe

communities,whereFlorestadecidualpresentedhigh

abun-dance ofgroups related to the nitrogen metabolism while

CampograminoideandCerradostrictosensupresentedhigh

abundance of groups related to carbon metabolism. Also,

Nitrosphaeraleswasthemostabundantorderfoundacross

thegradients,andfurtherstudiesareneededtoevaluatetheir

potentialinNcycling.

Conﬂicts

of

interest

Theauthorsdeclarenoconﬂictsofinterest.

Acknowledgments

Theauthorsthank“Fundac¸ãodeAmparoaPesquisanoEstado

doPiauí”(FAPEPI)forﬁnancialsupporttothisprojectthrough

ofPRONEX (FAPEPI/CNPq 004/2012). Wethankthe Unidade

Multiusuário doNúcleode Pesquisa eDesenvolvimento de

Medicamentos(UM-NPDM)fromFederalUniversityofCeará

forusingMiSeqIlluminasequencingfacilities.

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