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Vipin Chandra Kalia Editor

Microbial Applications

Vol.2

Biomedicine, Agriculture and Industry

MicrobialApplicationsVol.2

VipinChandraKalia Editor

Biomedicine,AgricultureandIndustry

Editor VipinChandraKalia

UniversityCampusDelhi

CSIR-InstituteofGenomics&IntegrativeBiology

Delhi,Delhi

India

ISBN978-3-319-52668-3ISBN978-3-319-52669-0(eBook) DOI10.1007/978-3-319-52669-0

LibraryofCongressControlNumber:2016034924

Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpartof thematerialisconcerned,speciﬁcallytherightsoftranslation,reprinting,reuseofillustrations, recitation,broadcasting,reproductiononmicroﬁlmsorinanyotherphysicalway,andtransmission orinformationstorageandretrieval,electronicadaptation,computersoftware,orbysimilaror dissimilarmethodologynowknownorhereafterdeveloped.

Theuseofgeneraldescriptivenames,registerednames,trademarks,servicemarks,etc.inthis publicationdoesnotimply,evenintheabsenceofaspeciﬁcstatement,thatsuchnamesareexempt fromtherelevantprotectivelawsandregulationsandthereforefreeforgeneraluse.

Thepublisher,theauthorsandtheeditorsaresafetoassumethattheadviceandinformationinthis bookarebelievedtobetrueandaccurateatthedateofpublication.Neitherthepublishernorthe authorsortheeditorsgiveawarranty,expressorimplied,withrespecttothematerialcontained hereinorforanyerrorsoromissionsthatmayhavebeenmade.Thepublisherremainsneutralwith regardtojurisdictionalclaimsinpublishedmapsandinstitutionalafﬁliations.

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Preface

Plants,humans,andmicrobesshowastronginteractionamongthemselves.Plants dependuponmicrobesfortheirgrowthanddevelopmentandforacquiringnutrients.Plantsinturnserveasfoodforhumanandanimals.Microbesintherhizosphereproducesecondarymetabolitestoprotectplantsagainstpathogensand toleratestress.Thehumanskinandgutharborawiderangeofmicrobes,which areresponsiblefortheirwell-being.Thisinteractionoflivingbeingsisgaining renewedinterestandvalue.Microbialactivitiesarequiteuniqueandinterestingand arefindingwiderapplicationsrangingfrombioremediation,bioenergy,biomedicine,agriculture,andindustry.Duringthepastcentury,therehasbeenatransition fromchemicalprocessestobiologicalmethods,largelybecausethelatterare eco-friendly.Now,theemphasishasshiftedfromonlyeco-friendlybio-processes toeconomicalaswell.TheGreenTechnologiesarethenewtrendtosavetheplanet Earththroughsustainableprocesses.Scientificprogresscanbegaugedprimarily throughbasicscientificresearch.Asmostscientificworksaresupportedthrough publicfunds,thereisaconstantdemandtoputthesefindingstoapplicationsfor humanwelfare.Students—therisingstarsandourscientistsinthemaking—are curioustolearnthebasicsciencesandhowthesecanbetranslatedintoproducts. Thisbookhasbeenbroughtouttocatertocuriousyoungmindsandprovide economicbenefitstothesociety.Inthisbook,thelearnedscientificcommunity hasputtheirbesteffortstosharetheirexpertise,whichtheyhavegainedthrough theirimmenseexperiencetargetedtowardunderstandingthemicrobialworld.This bookisatruereflectionofthesincerityofthescientificcommunity,whopromptly agreedtocontributetheircreationfortheyoungminds,whoarelikelytobenefitand takethisworldastepfurtherintothefuture.Iamtrulyhumbledbythehelp renderedbythecontributingauthors.Iamindebtedtoallofthem.Iamrunning shortofwordstoadequatelyacknowledgetheworthinessoftheirefforts.Mytrue inspirationstowritethispieceofworkstemfromthefaithinmeandtheconstant supportofthefollowingindividuals:thelateMrs.KantaKaliaandMr.R.B.Kalia (parents);Amita(wife);SunitaandSangeeta(sisters);Ravi,Vinod,andSatyendra (brothers);DakshandBhrigu(sons);myteachersespeciallyDr.A.P.Joshi;andmy

friendsRup,Hemant,Yogendra,Rakesh,Atya,Jyoti,Malabika,Neeru,and Ritusree.Imustalsoacknowledgethesupportofmystudentfriends—Sanjay, Mamtesh,Subhasree,Shikha,Jyotsana,andRavi.

Delhi,IndiaVipinChandraKalia

PartIBiomedicine

RoleofBacteriainNanocompoundFormationandTheirApplication inMedical ...............................................3

RubbelSingla,AnikaGuliani,AvneshKumari,andSudeshKumarYadav

MicrobialSourceofMelatoninandItsClinicalAspects .............39 SanjayKumar,BrendanPatrickMulligan,ShreeshOjha,andAlexTinson

MajorSourceofMarineActinobacteriaandItsBiomedical Application ...............................................55 RamBaskaran,ThenmozhiSubramanian,WuZuo,JiaxinQian, GaobingWu,andAshokKumar

AntimycobacterialAgents:ToTargetorNottoTarget .............83 AndaleebSajid,GunjanArora,RichaVirmani,andAnshikaSinghal

PartIIAgriculture

MicrobialBioﬁlm:RoleinCropProductivity ....................107

BhagwanN.RekadwadandChandrahasyaN.Khobragade

BacterialQuorumSensing(QS)inRhizosphere(PaddySoil): UnderstandingSoilSignalingandN-RecyclingforIncreased CropProduction ..........................................119 BhagwanRekadwadandChandrahasyaKhobragade

UseofPlantGrowth-PromotingRhizobacteriaasBiocontrolAgents: InducedSystemicResistanceAgainstBioticStressinPlants .........133 Marı´aVictoriaSalomon,Iva ´ nFunesPinter,PatriciaPiccoli, andRube ´ nBottini

BiologicalRoutesfortheSynthesisofPlatformChemicalsfrom BiomassFeedstocks ........................................153

Md.ImteyazAlam,MohammadAsifAli,ShelakaGupta, andM.AliHaider

PartIIIIndustry

GreenSynthesisofHydroxamicAcidandItsPotentialIndustrial Applications ..............................................169

BhatiaRaviKant,BhatiaShashiKant,BhallaTekChand, andBhattArvindKumar

BioactiveNaturalProducts:AnOverview,withParticularEmphasis onThosePossessingPotentialtoInhibitMicrobialQuorum Sensing ..................................................185

VijayKothari,PoojaPatel,andChinmayiJoshi

FungiImperfectiLaccase:BiotechnologicalPotentialandPerspectives ...203 BhagwanRekadwadandChandrahasyaKhobragade

Biosurfactants:AMultifunctionalMicrobialMetabolite ............213 NehaPanjiar,ShashwatiGhoshSachan,andAshishSachan

BioproductionofPolyhydroxyalkanoatefromPlantOils ............231

FakhrulIkhmaBinMohdFadzilandTakeharuTsuge

MicrobialSynthesisofPolyhydroxyalkanoates:Diversiﬁcation

QiWangandChangshuiLiu

Microbe-DerivedItaconicAcid:NovelRoutetoBiopolyamides

MohammadAsifAliandTatsuoKaneko

BasicsofMethanogenesisinAnaerobicDigester ..................291 VinayPatel,SoumyaPandit,andKuppamChandrasekhar

Laccases:BlueCopperOxidaseinLignocelluloseProcessing .........315 DayanandC.Kalyani,JogiMadhuprakash,andSveinJarleHorn

AbouttheEditor

VipinChandraKalia ispresentlyworkingasEmeritusScientist.Hehasbeenthe ChiefScientist,andtheDeputyDirector,atMicrobialBiotechnologyandGenomics,CSIR-InstituteofGenomicsandIntegrativeBiology,Delhi.HeisaProfessor ofAcademyofScientificandInnovativeResearch(AcSIR),Delhi.Heobtainedhis M.Sc.andPh.D.degreesinGeneticsfromtheIndianAgriculturalResearchInstitute,NewDelhi.Hehasbeenelectedas:(1)FellowoftheAssociationofMicrobiologistsofIndia(FAMI),(2)FellowoftheNationalAcademyofSciences (FNASc),and(3)FellowofNationalAcademyofagriculturalSciences (FNAAS).Hismainareasofresearcharemicrobialbiodiversity,genomics,and evolution,bioenergy,biopolymers,antimicrobials,quorumsensing,andquorum quenching.Hehaspublished101papersinscientificjournalssuchas(1)Nature Biotechnology,(2)BiotechnologyAdvances,(3)TrendsinBiotechnology,(4) CriticalReviewsinMicrobiology,(5)BioresourceTechnology,(6)International JournalofHydrogenEnergy,(7)PLoSONE,(8)BMCGenomics,(9)Gene,and (10)AnnualReviewofMicrobiology.Hisworkshavebeencited3558timeswitha hindexof31andani10indexof66.Hehasedited3books:Quorumsensingversus quorumquenching:Abattlewithnoendinsight(2015,SpringerIndia),Microbial FactoriesVol1and2(2015).HeispresentlytheeditorinchiefoftheIndianJournal ofMicrobiologyandEditorof(1)PLoSONE,(2)JournalofMicrobiology& Biotechnology(Korea),(3)AppliedBiochemistry&Biotechnology(USA),(4) InternationalScholarlyResearchNotices(Energy),(5)DatasetPapersinScience (Microbiology),and(6)JournalofMolecularandGeneticMedicine.Heisalife memberofthefollowingscientificsocieties:(1)SocietyofBiologicalChemistsof India(2)SocietyforPlantBiochemistryandBiotechnology,India;(3)Association ofMicrobiologistsofIndia;(4)IndianScienceCongressAssociation;(5) BioEnergySocietyofIndia,and(6)theBiotechResearchSocietyofIndia (BRSI).HeisalsoamemberoftheAmericanSocietyforMicrobiology.

RoleofBacteriainNanocompound FormationandTheirApplicationinMedical

RubbelSingla,AnikaGuliani,AvneshKumari,andSudeshKumarYadav

Abstract Nanotechnologyhasnowreachedtoastagewherethenanoparticles (NPs)havebeeninapplicabilityinwide-rangingrealmsofscienceandtechnology. NPsarethematerialswithatleastonedimensionintheorderof100nmorless.NPs displayastonishingpropertiesofhighsurface/volumeratioandenhancedphysical, chemical,optical,andthermalpropertieswhichareextremelydifferentthantheir bulkmaterials.Theconventionalmethodsofsynthesisofnanocompoundsinvolve theemploymentofphysicalandchemicalmethods,whichhavefewdrawbacks suchastherequirementoftoxichazardouschemicals,energyintensive,andcostly processesmakeitdifﬁculttobewidelyimplemented.Toovercometheselimitations,theresearchershavelookedforwardforaneasyandfeasiblealternative approachforthesynthesisofnanocompounds.Theemploymentofalternative biogenicroutefortheNPsynthesisbyusingbiologicalentitiesofunicellularliving organismssuchasbacteria,fungi,andactinomyceteshassoughtapparentattention ofthescientiststhroughouttheglobalearth.Agreenerapproachinterconnecting nanobiologywithmicrobialbiotechnologyisresponsiblefortheformationofNPs mediatedbymicrobesthatallowsynthesisinaqueousenvironment,withlow energyconsumptionandatlowcosts.Biosynthesisofgold,silver,copper,quantum dots,andmagnetiteNPsbybacteria,fungi,actinomycetes,andyeastshasbeen reported.InaviewtoformnoblemetalNPsofuniformshapeandsize,biological routesusingmicrobialculturesatoptimaltemperature,pressure,andpHhavebeen

R.Singla•A.Guliani

A.Kumari

BiotechnologyDivision,CSIR-InstituteofHimalayanBioresourceTechnology,Councilof ScientiﬁcandIndustrialResearch,Palampur,HimachalPradesh,India

S.K.Yadav(*)

BiotechnologyDivision,CSIR-InstituteofHimalayanBioresourceTechnology,Councilof ScientiﬁcandIndustrialResearch,Palampur,HimachalPradesh,India AcademyofScientiﬁcandInnovativeResearch(AcSIR),NewDelhi,India CenterofInnovativeandAppliedBioprocessing(CIAB),160071,Mohali,India e-mail: sudeshkumar@ihbt.res.in; skyt@rediffmail.com

V.C.Kalia(ed.), MicrobialApplicationsVol.2,DOI10.1007/978-3-319-52669-0_1

formulated.Inthischapter,themainfocusisgivenontheintracellularand extracellularapproachesusedforsynthesisofmetallicNPsbyvariousmicrobial species.Adetaileddiscussionisprovidedtoexplainthevariousfactorswhich affectthesynthesisofnanocompoundstofurtheraugmentthegrowthrateofNPsas wellasthemechanismofactionatthecellular,biochemical,andmolecularlevel.A greatstressisgivenontheroleofthesenanocompoundsinthemedicalﬁeldforthe diagnosticanddiseasetreatment.Thepotentialofgreatbiodiversityofmicrobial culturesasbiologicalcandidatesleadingtothemanufacturingofNPsisneededto befullyinvestigated.

Keywords Microbialsynthesisofnanocompounds•Metalnanoparticles• Theranostics•Anti-microbialagents•Diseasetherapy

1Introduction

Theterm“nano”hasitsoriginfromtheGreeklanguagemeaningofminiaturized objectsofonebillionth(10 9)insize.Nanoparticles(NPs)aretheparticleshaving atleastonedimensioninthenanometerscale,i.e., 100nm.Nanocompoundshave attractedagreatattentionduetotheircharacteristicuniqueelectronic,optical, physical,chemical,electrical,mechanical,magnetic,thermal,dielectric,andbiologicalpropertieswhichareabsolutelydifferentfromtheirbulkcounterparts(Jain etal. 2008;Kato 2011).ThemetalNPshaveanupperhandwhencomparedtothose metalcompoundsatmolecularlevelduetotheirenhancedRayleighscattering, surfaceplasmonresonance(SPR),surface-enhancedRamanscattering(SERS)in metalNPs,quantumsizeeffectinsemiconductorquantumdots,andsupermagnetismbehaviorinmaterialswithmagneticproperties.Interestingly,cuttingdownthe dimensionsofNPshasaclear-cuteffectonthebehaviorofmaterialsatnanoscale. ThesephysicalpropertiesofNPsareduetotheirgreateraspectratio(surfaceareato volumeratio),spatialconﬁnement,greatersurfaceenergy,andreducedimperfections.NPshavevariousapplicationsinbiomedical,cosmetics,optics,electronics, spacetechnology,energy,catalysis,food,andmanymore(RosarinandMirunalini 2011;SolomonandD’Souza 2011).

FortheNPsynthesis,twodifferentstrategies,namely,“top-down”and“bottomup,”areused.Intheformercase,large-sizedmaterialsareconvertedtosmaller oneswiththehelpofreducingagents,whereasincaseofbottom-upapproach,the atomsareassembledintolargermolecularstructuresatnanometerscale(Alietal. 2015).Anoverwhelmingnumberofchemicalandphysicalprocessesarepopular thataretakenintoaccountformanufacturingofmetallicNPs(likesilver,gold, copper,magnetites,andsemiconductorquantumdots)usingthesetwoapproaches. Theseconventionalsynthesisproceduresareinefﬁcientinmaterialandenergy usage,laborious,andcapital-intensiveandproducetoxicwastesasendproducts (Thakkaretal. 2010)andinvolvetheemploymentofharmfulchemicalsubstances, intensereactionconditions,andelectrochemicaltechniques.Toovercomethese limitationsassociatedwiththetraditionalmethodsandtoincreasethe

biocompatibilityofnanocompounds,theresearchinthecurrentscenarioisdirected tolookforthereliable,eco-friendly,andsustainableapproachesforthedevelopmentofNPsofdesirableshapeandsizeswithexcellentpropertiesofdispersityand stabilitycausingminimalornoharmtothelivingsystemsandenvironment (Chauhanetal. 2011).Inawaytoachievetheextensivescopeofnanocompounds, thepotentialofmicroorganismsisrealizedforthesynthesisofmetalNPs.The microbe-mediatedsynthesisofnanomaterialhasattractedthegreatscientiﬁcworld acrosstheworld.

BiogenicNPssynthesizedbyusingthelivingentitieslikebacteria,fungi,and actinomycetesarehighlystablewithbetterspeciﬁcityandcatalyticreactivityas theyhelptomaintainabettercontactbetweentheenzymeandmetalsaltbecauseof microbialcarriermatrix.Themicrobesarewidelyabundantinnaturalecosystems andcanbeculturedinasuitablegrowthmedia(Lietal. 2011).Apartfromthe advantagesofbiologicalsynthesis,theexploitationofmicrobialspeciesforthe manufacturingofnanoscaleparticlesalsopossessessomedrawbacksofculture maintenancewhicharequitecomplexandtakealongdurationtogrow.The microbe-mediatedsynthesisapproachesdonotprovidecontroloversizedistributionandshapeofnanostructures.EventheformedbiogenicNPsarepolydispersein natureandproductionrateissoslow(NarayananandSakthivel 2010).Despiteof theseproblems,therearestillchancestogaininsightintothebacterialsynthesisof NPsthroughtheprocessoptimizationofreactionparameterssuchasmicrobial strainselection,ageandconcentrationofcultureused,pH,temperatureandtimeof incubationofthereactionmixture,andconcentrationandtypeofmetalsaltsused (Punjabietal. 2015).Theestablishmentandimplementationoftheseoptimization processeswillprovidehopefortheuseofNPssynthesizedbymicrobesonalarge scaleandformarketableapplications.

ThebiosynthesisofmetallicNPstakesplacewhenthemicroorganismscapture ionsofinterestfromtheirsurroundingenvironmentandconvertthemetalionsinto theelementalformofmetalsthroughtheinvolvementofvariousenzymesreleased bythecellactivities.MicroorganismcansynthesizemetalNPsthroughtwomechanisms,i.e.,metalbioreductionandbiosorption.Theﬁrstisbioreduction,inwhich metalionsarechemicallyreducedintomorestableformsbiologicallyinwhichthe reductionofametalioniscoupledwiththeoxidationofanenzyme.Microorganismspossessingtendencyofmetalbioreductioncancolonizemetal-contaminated surroundings(Deplancheetal. 2010).Biosorptionisaphenomenoninwhich microbesaresurroundedbytoxicheavymetalsintheirsurroundingsleadingto stressconditions.Themetalionsbindtothecellwall;thereleasedpeptidesorother cellwallcomponentsbindtothesemetalionsandformstablenano-complexes (Yongetal. 2002).

ThesynthesisofNPsmediatedbymicrobesoccursmainlybytworoutes,e.g., intracellularandextracellular.NPformationthroughtheuseofmicrobesisan exampleofbottom-upapproach,wheretheﬁrststepofreactiondealswiththe reduction/oxidationofsubstratesandthenthedevelopmentofcolloidalformations (Moghaddam 2010).Intheintracellularmechanism,metalionscrossthemicrobial cellmembraneandaretransportedinsidetoformNPsinthepresenceofenzymes. Themicrobialenzymesactasreducingagentsresponsibleforreductionofmetal

saltsintonano-forms.Reducedmetalatomsnucleatewithsubsequentgrowthfor thegenerationofnanostructures.TheextracellularapproachofNPsynthesis involvesentrappingofthemetalionsonthemicrobialcellsurfaceandreducing themetalionsinthepresenceofenzymes(Zhangetal. 2011).DuetothebiocompatibilityofthesebiosynthesizedmetalNPs,theygenerallyfindapplicabilityinthe medicalfields.ThemetalNPsfindawidespaceforthediseasediagnosticsaswell asforthetreatmentofcertaindiseases.ThesemetalNPspossessgreatantibacterial potentialwhichallowstheutilityofthesenanostructuresinthemedicalfields. Microbe-mediatedsynthesisofmetalNPsisapromisingapproachwhichconnects microbialbiologywithbiotechnologyandnanotechnology.Thereisaneedto explorethisareatosearchtheenvironmental-friendlyandcost-effectiveprocedures forthedevelopmentofnanomaterialstorealizethefullpotentialofmetalNPsinthe medicalaswellasotherspheresoflife.

2RoleofBacteriainNanocompoundFormation

Recentlyscientistshavestartedfocussingonprokaryotesforsynthesisofmetallic NPs.Duetotheirubiquitousnature,abundanceinenvironment,andabilitytotolerate diverseconditions,bacteriaareagoodchoiceforthispurpose.Bacteriaarefast growing,easytomanipulate,andinexpensivetocultivate.Bacteriaareconsideredas potentialbio-candidateforthesynthesisofmetallicNPslikegold(Au),silver(Ag), platinum(Pt),palladium(Pd),titanium(Ti),andsoforth.Bacteriatendtosynthesize inorganicmaterialsatnanoscaledimensionsbyeitherintracellularorextracellular mechanisms.Mostoftheionsofmetalsaltscancauseharmtobacteria,andhencethe metalreductionbythemicrobesisaparticularkindofdefensemechanismgenerated toprotectthemfromsuchtoxicity.Microbesbecomeresistanttohazardousheavy metalsbecauseofchemicaldetoxiﬁcationaswellasoutwardmovementofenergydependentionsfromthecellthroughsomemembrane-boundproteinswhichactas ATPaseoraschemiosmoticcationorprotonanti-transporters.Variationinsolubility playsadeterministicjobformicrobialresistance.Thelocationofthereductive componentspresentinthecellalsoaffectstheformationofmicrobe-mediatedNP synthesis.Whentheenzymespresentonthecellmembraneactasreducingagents andareinvolvedinmetalionreduction,thenextracellularformationofmetalNPsis quiteobvious.NPsproducedbyextracellularpathwayhaveapplicationsindifferent spheres,i.e.,optoelectronics,electronics,bio-imaging,andsensingtechnology,than intracellularaccumulation.

2.1IntracellularBiosynthesis

ForintracellularsynthesisofNPsusingmicrobialculture,thebacterial/fungal cultureisgrowninaspeciﬁcliquidgrowthmediaincubatedonashakeratacertain optimaltemperature.Aftercompleteincubation,thecultureﬂaskiskeptunder

staticconditionstoallowthemicrobialbiomasstosettledown;afterthattheculture supernatantisdiscardedandthecellsarewashedwithdistilledwater(Punjabietal. 2015).Thisstepofcellwashingisrepeatedseveraltimesandthesupernatantis discardedeachtime.Thebiomassseparatedbycentrifugationisfurtherexposedto aqueoussolutionofmetalsatdifferentconcentrations.Thecultureisthenincubated onashakeratasuitabletemperatureuntilavisualchangeincolorisobserved.A colorchangefrompaleyellowtobrownishcolorindicatesthesynthesisofsilver nanoparticles(AgNPs);paleyellowtopinkishorpurplecolorrepresentsthe formationofgoldnanoparticles(AuNPs).

2.2ExtracellularBiosynthesis

NPsaresynthesizedbyextracellularbiosynthesismechanismwherethetestmicrobialstrainisgrowninanappropriategrowthmediaandincubatedunderparticular growthconditionsliketemperatureandshaking.Afterincubation,theculturebroth iscentrifugedandthesupernatantisusedforsynthesisofNPs.Theculture supernatantisaddedtothesolutionofmetalionsatanoptimizedconcentration andthenincubatedforaperiodof72h.Thevisiblecolorchangeinthereaction mixtureisnoticedafteraparticulartimewhichconﬁrmsthebiosynthesisofNPsin thesolution(Punjabietal. 2015).

2.3SynthesisofMetalNanocompounds

Intherecenttimes,prokaryotesareinhighdemandforthebiosynthesisofNPs.The metalNPsareformedfromthereductionofbulkmetalsalts.Inthissection,we havetriedtosummarizevariousmetallicNPslikesilver,gold,copper,magnetic NPs,andquantumdotssynthesizedusingdifferentspeciesofmicrobeslikebacteria,fungi,andactinomycetes.

2.3.1SynthesisofSilverNPs(AgNPs)

AgNPsarethosepreparedfromdifferentsilversaltslikesilverchloride(AgCl2), silveriodide(AgI2),andsilvernitrate(AgNO3)havingsizerangeof1–100nm.The importantmethodstakenintoaccountfortheformationofAgNPsincludethe chemicalandphysicalmethods.Buttheonlydisadvantagebehindtheuseof thesetwoapproachesincludeshighcostofpreparation.Tomakethecost-effective synthesis,biologicalapproachusingmicrobeshasbeensupposedasanalternate. ManybacterialstrainsusedforthesynthesisofAgNPsincludeeitherextracellular orintracellularsynthesisapproaches.Intracellularsynthesisinvolvestheuseof extramaterialslikesurfactantsorultrasoundtreatmenttoreleasesynthesizedNPs. Extracellularsynthesisischeap,requiresdownstreamprocessing,andisusefulfor large-scaleproductionofAgNPs.

AgNPshavebeensynthesizedbythemicrowaveirradiationofculturesupernatantsof Bacillussubtilis.SynthesizedAgNPshavesizeintherangeof5–50nm. Microwaveirradiationresultedinuniformheatingandreductionofaggregation aroundAgNPs(Saifuddinetal. 2009).AgNPshavebeensynthesizedintracellularly andextracellularlyusing Bacillus strainCS11.AgNO3 solutionhasbeenaddedto thenutrientbrothcontainingbacterialbiomassandincubatedfor72hatroom temperatureinthepresenceoflight.Avisiblecolorchangeofthemediumfrom paleyellowtobrownindicatestheformationofAgNPs.Themechanismforthe bioreductionofsilveriontoAgNPsisstillunclear,althoughitisconsideredthat someenzymeslikenitratereductasesecretedbythemicrobesareresponsiblefor thereduction(Dasetal. 2014).AgNPscanalsobesynthesizedbyaddingthe AgNO3 solutiontothesupernatantofthebacterialculturesof Bacillussubtilis, Lactobacillusacidophilus, Klebsiellapneumoniae, Escherichiacoli, Enterobacter cloacae, Staphylococcusaureus,etc.Theextracellularmetabolitesexcretedbythe culturesreducethesilverionsintoAgNPsinthepresenceoflight(Shahverdietal. 2007). E.coli wasalsousedfortheextracellularsynthesisof40–60nm-sized AgNPs.Theeffectofgrowthmediaandincubationperiodwasexaminedonthe formationofAgNPsandobservedthatluriabroth(LB)mediumandstationary phasehavethemaximumpotentialforthesynthesisofAgNPs(Natarajanetal. 2010).

TheuseoffungalspecieshasalsobeenreportedfortheformationofAgNPs. Thefungus-mediatedformationofAgNPsisbasedonthemechanismthatthe fungalcellstrapAgionsonitssurfacefollowedbythereductionwiththehelpof releasedenzymes.Thefungalspecies Aspergillusterreus hasbeenreportedearlier leadingtoformationofAgNPsbyextracellularNADH-dependentreductase enzyme(Lietal. 2012).ExtracellularbiosynthesisofAgNPsbytheuseof Fusariumoxysporum isbasedonthereductionofmetalionsbynitrate-dependent reductaseenzymeandshuttlequinoneprocess(Duranetal. 2005).Fungiproduce largeamountsofAgNPsascomparedtobacteriaduetothesecretionofalarge amountofproteinsbyafunguswhichisresponsibleforformationofAgNPs.The synthesisofAgNPsbyotherbacteriaandtheirsizerangearetabulatedinTable 1

2.3.2SynthesisofGoldNPs(AuNPs)

AuNPsaretheparticlesrangingindimensionsof3–150nmwhichalsoknownas colloidalgoldandpossessmanydistinctivepropertieswhichmakethem“star” amongotherNPs.AuNPshaveatendencytochangethecolorofcolloidalsolutions dependingupontheirsizes.TheimportantpropertiesofAuNPsarehighsurfaceto volumeratio;optical,electrochemical,andcatalyticproperties;lowtoxicity;easy toprepare;easilydispersedinliquids;easeofsurfacemodiﬁcation;etc.Many bacterialstrainshavebeenusedfortheintracellularandextracellularsynthesisof AuNPs.Theuseofmicrobesforthisfunctionisfoundtobeeasy,economical,and eco-friendly.Abriefdescriptionaboutthemicrobialsynthesismethodsandfew relatedexamplesforthepreparationofAuNPsarementioned.

Table1 Size,range,andlocationofsynthesisofdifferenttypesofmetallicnanocompoundsby theuseofdifferentkindsofmicrobialspecies

Typeofmicrobes

Pseudomonas antarctica

Synthesis location

Typeof NPs synthesizedSizeandshapeofNPsReferences

ExtracellularAgNPsSphericalshaped, 6–13nm Shivajietal. (2011)

Bacillus CS11ExtracellularAgNPsSpherical,42–92nmDasetal.(2014)

Idiomarina sp PR58–8

Pseudomonas meridian

IntracellularAgNPsSpherical,26nmSeshadrietal. (2012)

ExtracellularAgNPsSphericalshaped, 6–13nm Shivajietal. (2011)

Humicola sp.ExtracellularAgNPsSpherical,5–25nmSyedetal. (2013)

Pleurotus ostreatus

Aspergillusniger

Proteusmirabilis PTCC1710

Penicillium chrysogenum

Aspergillus sydowii

Pseudomonas ﬂuorescens

Aspergillusniger

Fusarium oxysporum

Aspergillus fumigatus

Pseudomonas ﬂuorescens

Salmonella typhimurium

Pseudomonas stutzeri

Magnetospirillum magnetotacticum

Geobacter metallireducens

E.coli

ExtracellularAgNPsGrainshaped,8–50nmDevikaetal. (2012)

Extracellular and Intracellular AgNPsSphericalshapes, 43–63nm Vanajaetal. (2015)

Extracellular and Intracellular AgNPsSpherical,10–20nmSamadietal. (2009)

IntracellularAuNPsSpherical,triangle,and rodshaped,5–100nm

Sheikhlooand Salouti(2011)

ExtracellularAuNPsSpherical,8.7–15.6nmVala(2014)

ExtracellularAuNPsSpherical,50–70nmRadhika Rajshreeand Suman(2012)

ExtracellularAuNPsSpherical, 12.79 5.61nm Bhambureetal. (2009)

ExtracellularAuNPsShapenotdeﬁned, 22nm Thakkeretal. (2013)

IntracellularAuNPsSpherical,irregularly shapedwithindeﬁnite morphology, 85–210nm Bathrinarayanan etal.(2013)

ExtracellularCuNPsSphericalandhexagonalshaped,49nm Shantkritiand Rani(2014)

ExtracellularCuNPsSpherical,49nmGhorbanietal. (2015)

ExtracellularCuNPsSpherical,8–15nmVarshneyetal. (2010)

IntracellularIronoxide NPs Cuboctahedral,50nmLeeetal.(2004)

ExtracellularIronoxide NPs Tabularshapedwith 20–200nmlengthand 20–70nmwidth

Valietal.(2004)

ExtracellularCdTeSpherical,2–3nmBaoetal. (2010a, b) (continued)

Table1 (continued)

Typeofmicrobes

Phanerochaete chrysosporium

Fusarium oxysporum

Brevibacterium casei

Aspergillus terreus

Synthesis location

Typeof NPs synthesizedSizeandshapeofNPsReferences

ExtracellularCdSGrainshaped,2.56nmChenetal. (2014)

ExtracellularCdTePolydispersespherical, 15–20nm SyedandAhmed (2013)

IntracellularCdSPolydispersespherical, 10–30nm Pandianetal. (2011)

ExtracellularPbSePolydispersespherical, 20–50nm Jacobetal. (2014)

ThebiosynthesisofAuNPshasbeenreportedfrom Pseudomonasaeruginosa and Rhodopseudomonascapsulata,wherebythecell-freesupernatantofthesetwo strainsismixedwithhydrogentetrachloroaurate,indicatingthecolorchangeof solutiontopurpleorredwine,furtherconfirmingtheformationofAuNPs.ThepH ofthesolutionisthedecidingfactorfortheshapeandsizeofNPs.AtpH4and 7,nanoplatesandsphericalNPsofsizerange10–20nmareformed,respectively (SinghandKundu 2014).CubicAuNPsareformedwhenafilamentouscyanobacterium, Plectonemaboryanum UTEX485,reactswithaqueousAu(S2O3)23 solutionat25–100 Cfor1month,andoctahedralAuNPsareformedafterreacting AuCl4 at200 Cfor1day(Lengkeetal. 2006).Differentfungalstrainsarealso knownforbothextracellularandintracellularsynthesisofmetallicAuNPs. Phanerochaetechrysosporium (fungalmycelium)istreatedwithHAuCl4 under ambientconditionstoformAuNPswithin90minbytheproteinsecretedbyfungus itself.TheextracellularandintracellularproductionofAuNPsisduetothesecretionofenzymeslacaseandligninasebyfungus,respectively(Sanghietal. 2011). Verticillium speciesoffungushasalsoledtotheformationofAuNPsbythe reductionofaqueousAuCl4 ions(Mukherjeeetal. 2001).Theenzymespresent withinthecellwalloffungiareknowntoreducetheions.Aspecies-specific NADH-dependentreductase,releasedby Fusariumoxysporum,hasalsobeen usedforreducingAuCl4 ionintoAuNPs(Mukherjeeetal. 2002).

Thermomonospora,anextremophilicactinomycete,alsoreducesAuionsto AuNPsextracellularly.Theharvestedbiomassisaddedtosolutionofchloroauric acidandkeptindarkforthesynthesisofmonodisperseAuNPs,wherebyenzymatic processesplayadeterministicjobinthereductionofmetalionsaswellasAuNP stabilization.Theproteinssecretedbyactinomycetebiomassactascappingagents forthestabilizationofAuNPs(Sastryetal. 2003).Thebiomassofotheractinomycetes, Streptomycesviridogens,hasalsobeenaddedtochloroauricacidsolution, andthecolorofbiomasschangestopinkwithin24hoftimeindicatingthe formationofAuNPswithinthecells.ThesesynthesizedAuNPspossess antibacterialactivityagainst S.aureus and E.coli (Balagurunathanetal. 2011).

2.3.3SynthesisofCopperNPs(CuNPs)

CuNPsynthesisisagreatchallengeasCuatnanometerscaleisnotsostableand easilyoxidizedtogetconvertedintocopperoxides(CuO).Therefore,itisofgreat needtofurtherstabilizeCuNPsaftertheirsynthesissoastousetheminvarious applications.CopperasmetalorCuOatnanoscalepossessuniquepropertiesasitis anessentialpartoflivingbeingsthatplaysabeneﬁcialroleinbiomedicalapplications.TheresearchonCuNPshasbecomeafocalpointduetotheirunique propertiesandlowcostofpreparationandutilityinawidearrayofapplications. CuNPsholdgoodthermalandelectricalconductivity,aswellasopticalproperties. AmicrobialapproachhasbeenusedforthesynthesisofCuNPsbyincubating coppersulfatesolutionwiththecellpelletandcell-freesupernatantof Pseudomonasﬂuorescens.Spherical-andhexagonal-shapedNPsof49nmwereformed (ShantkritiandRani 2014).Thesupernatantofanotherbacterialculture S.typhimurium wasincubatedwithaqueoussolutionofcoppernitratetoform CuNPsofsize49nm(Ghorbanietal. 2015).Fungi,suchas Penicillium sp.and F.oxysporum strains,havealsobeenreportedtobiosynthesizeCuOandCu2SNPs. Afungusknownas Stereumhirsutum hasalsobeenusedforthesynthesisofCuand CuONPs(Cuevasetal. 2015).ThesynthesisofCuorCuONPscanleadtodifferent SPRwhichisformedduetothestrongcouplingbetweenincidentelectromagnetic radiationandsurfaceplasmoninmetalNPs.

2.3.4SynthesisofMagneticNPs(MNPs)

MNPsareofgreatpotentialinthepresenteraastheypossessmagneticbehavior withutilityindiverseﬁelds.Theresearcherspaymoreattentiontothesynthesis methodsofMNPssoastoformuniform-sizedMNPsbecausethepropertiesof MNPsaresizedependent.ThethreemajorfunctionalpartsofanMNPcarrier includeamagneticcore,asurfacecoat,andafunctionaloutercoating.Theinner magneticcoreconsistsofasupramagneticmolecule(Fe,Ni,Co,etc.)which dependsuponitsapplication.Thesurfacecoatisusedtoprovidestericrepulsions, toincreasethestabilityandtorestrainagglomerationoftheparticles.The functionalizedoutercoatingmayattachanyligandorthebiologicallyactiveentity (Kumarietal. 2014).

Magnetotacticbacteria(MTB)producemagneticnanocrystalsorMNPswhich areenvelopedbycertainbiomembranescalledmagnetosomes(Alphanderyetal. 2008).Theybiomineralizemembrane-boundmagneticnanocrystalsoftheiron oxide(Fe3O4)orironsulﬁde(FeS4)(BazylinskiandFrankel 2004).Insidethe bacterialmembrane,themagnetosomesareorganizedinachain-likemanner whichofferstrongmagneticdipoleforbacteriatohelpmovealongtheearth’s magneticﬁelddirection(Alphanderyetal. 2008).MTBsarefoundinmarineand freshwatersources.FreshwatermilieuswerefoundtocontainvariousmorphologicaltypesofMTB,includingrod-shaped,comma(vibrio),coccoid,andhelicoidal

forms. Alphaproteobacteria and Magnetobacteriumbavaricum aresomeofthe MTBsfoundinfreshwaterenvironments.BothFe3O4 andFe3S4 producer MTBshavebeenfoundinmarineenvironments.

Thestrainsof Magnetospirillummagneticum produceeitherFe3O4 magnetic NPsinchainsorFe3S4 (greigite),whilesomeotherstrainsproducebothtypesof NPs(Rohetal. 2001). Fusariumoxysporum and Verticillium speciesareableto formironoxidesmainlyFe3O4 byhydrolyzingtheionprecursorsextracellularly (Bhardeetal. 2006).Magnetosomescanhavesquare-like,rectangular,hexagonal, orbullet-shapedprojections.

2.3.5SynthesisofQuantumDots(QDs)

SemiconductornanocrystalsarethetypeofinorganicNPsdiscoveredintheearly 1980sranginginsizebetween1and10nm.Theserepresentastateofmatterinthe transitionregimebetweenthemoleculesandthebulksolid.Alayeroforganic ligandsatthesurfaceofsemiconductorNPsstabilizestheminthecolloidalform. Theligandconsistsoftwoparts:apolarheadgroupthatpossessestheaffinityfor theattachmenttothesurfaceofsemiconductornanocrystalsand,asecondpart,a tail,whichhelpsinthesolubilizationofsemiconductornanocrystalsintheorganic media.Thepropertiesofsemiconductornanocrystalsariseduetothespatial arrangementsofatomsinthecrystallinelattice.Theopticalandelectronicpropertiesofsemiconductornanocrystalscanbevariedwiththereductioninthesizeof nanocrystals,andthephenomenacanbedescribedbytheterm“sizequantization effect.”Thequantumdots(QDs)arethesmall-sizedsemiconductornanocrystalsto befitinthequantumconfinementregion.

AfacileandbiocompatibleroutehasbeendevelopedtosynthesizeCdSeQDs using Escherichiacoli cellsasamatrix.TheQDsextractedfromsuchcellsshowed asurfaceproteinlayerwhichactedtoimprovethebiocompatibilityofQDs(Yan etal. 2014).YeastcellshavebeenreportedtosynthesizebiocompatibleCdTeQDs ofsize2–3.6nmwitheasilytunableﬂorescenceemissioncapacity.Anextracellular growthpathwayisknowntoberesponsiblefortheformationoftheprotein-capped CdTeQDs(Baoetal. 2010a).Thefungus Fusariumoxysporum hasbeenreported tosynthesizeCdTeQDsextracellularly.Thereisnoneedtoaddstabilizingagents asformedQDsarealreadycappedbyanaturalprotein(SyedandAhmad 2013).

3FactorsAffectingNPSynthesisbyMicrobes

ThesizeandshapeofNPsarealteredbythevariationincertainphysicaland chemicalpropertiesofNPs.VariousfactorsaffectingthesynthesisofNPsbythe microbesincludetheageandconcentrationofcellcultureused,natureandconcentrationofmetalionused,pH,temperatureofreactionmixture,andincubation timewhichplaysagreattaskinthemicrobe-mediatedsynthesisofNPs.Theroleof eachfactorandhowitaffectsthesynthesisofNPsaredescribedbelow.

3.1AgeandConcentrationoftheMicrobialCellCulture

Theageandconcentrationofthemicrobialcultureusedforthesynthesisofmetallic NPshavedeterministiceffectonthesizeandshapeofNPsasthemetabolic activitiesofthecellsvarywiththeage.Ageofculturehaspronouncedeffecton NPsynthesis(MaliszewskaandPuzio 2009).Withtheincreaseinconcentrationof biomassused,thereisanincreaseintheproductionofNPs.Itisspeculatedthatthe enzymespresentintheorganismsalsoknownasbiocatalystsareresponsiblefor biologicalsynthesisofNPs.Thesebiocatalystsareusedintheformsofpuriﬁed enzymes,wholecells,andcrudeenzymes.Inrespecttoﬁndtheoptimumageof culturedmicrobialcellsforNPformation,theculturedcellsareharvestedat differentphasesofgrowth(lag,earlystationary,latestationary).Forexample, synthesisofAuNPsusingcell-freesupernatantof Geotrichumcandidum showed thatthecellmassharvestedat48hofgrowthproducedmaximumamountof AuNPs.Thereasonbehindmaybeduetotheemergenceofmaximumamountof reducingagentsat48hgrowthwhichresultedinhigherreductionofmetalsaltsinto NPs(Mittaletal. 2013).

3.2ConcentrationofMetalSalt/SubstrateUsed

Inbiotransformations,oneoftheimportantfactorsistofindthemaximumconcentrationofsubstratewhichcouldbeconvertedintofinalendproductwhichmakes thereactionmorecost-effectiveandefficient.Concentrationofinitialsubstrate/ metalionusedhasapredominanteffectontheshapeandsizeofsynthesizedNPs. Increasingtheconcentrationofsilvernitratesolutionfrom1mMto5mMinthe reactionmixtureisknowntoincreasetheparticlesize.Eventheparticleagglomerationisknowntooccurwhenhighconcentrationsofmetalsalts(10mM)areused inthesynthesisreactionandalsotheproductionofAgNPsdecreased.Itisalso reportedthattheuseofhigherconcentrationofAgNO3 hascertaintoxiceffectson F.oxysporum biomass(thebiocatalyst).ForthebiosynthesisofAgNPs,theoptimumconcentrationofsilvernitrateshouldbearound5mM(Korbekandietal. 2013).Similareffectsofmetalsaltconcentrationarenoticedonthesynthesisof AuNPsbytheuseof Penicilliumcrustosum wheretheincreaseinconcentrationof AuCl4 (mM)causesadecreaseintheaveragediameterofparticlesbutsizebeginto increaseatevenhigherconcentrationofsaltused(Barabadietal. 2014).Thisis explainedbasedonthefactthatincreaseintheconcentrationofmetalsaltusedfor reductionintonanoscale-sizedparticlesallowsthegrowthofNPsatafasterrate. Moreover,particlesinhighersaltconcentrationmayhaveatendencytoaggregate andproducebiggerparticles.

pHofthereactionmixtureisacriticalfactorwhichinfluencesthesizeandshapeof NPsatalargeextent.AgNPsofdifferentsizeandshapecanbeobtainedby controllingtheenvironmentofNPsynthesis(Correa-Llantenetal. 2013).IncreasingpHresultedintheformationofAgNPsofsizerange10–20nm,whiledecreasingthepHto4resultedintheformationofsilvernanoplates(Correa-Llantenetal. 2013).Inanotherstudy,acidicpHresultedintheformationof45nm-sizedAgNPs, whereasatpH10,AgNPsobtainedwereofjust15nm.ThepHwasfoundtobea vitalfactoralsoaffectingthesynthesisofAuNPsinmicrobialcultures.Alterations inpHduringcontacttoAuionshaveadirecteffectontheshape,size,andnumber ofNPsformedpercell.AuNPssynthesizedin V.luteoalbum afterexposureto HAuCl4 for24hatpHvaluesof3,5,7,and9wereexaminedinastudybyGericke andPinches(2006).AuNPsformedatpH3werecomparativelyuniforminsize wheremajorityofNPswereofsphericalshapehavingadiameterlessthan10nm. AtpH5,thesynthesizedAuNPsweresmallsphericalparticles,similartothoseNPs formedinthereactionmixtureatpH3.Apartfromthis,agreatquantityoflargesizedNPsoffewmorevariableshapes,e.g.,triangles,spheres,hexagons,androds, arealsosynthesizedatthispH.TheshapesofformedAuNPsatpH7weresimilarto particlesobservedatpH9whichincludedsmallsphericalaswellasbiggerparticles ofirregular,undefinedshapes.AnotherstudywhereAuNPshavebeensynthesized bywholecellsupernatantsof Geotrichumcandidum demonstratedthatthesynthesisofAuNPsisoptimumatpH7,whereasatpHaboveandbelow7,particle aggregationisobserved(Mittaletal. 2013).ThesynthesisofmetalNPsofvariable shapesbytheuseofreactionmediaatdifferentpHvaluessignifiesthatthevariation inthisfactortendstocontroltheparticlemorphologyduringoptimizationofa synthesisprocess.

3.4Temperature

TheenvironmentofNPsynthesissuchastemperature,oxygenation,andincubation canbeeasilycontrolledandmanipulated.ThesizeofAgNPsisalsoaffectedbythe reactiontemperature.IncreaseintemperatureleadstotheformationofsmallersizedAgNPs.TheformationofmanyseedcrystalsisthereasonbehindtheshapecontrolledsynthesisofAgNPsbycontrollingcertainenvironmentalfactors.Lower (acidic)pHandlowertemperaturesofthereactionmixtureleadtolessernucleation fortheformationofAgNPswherenewAgatomsgetdeposittobuildlarge-sized NPs.ButwithanincreaseinpHaswellastemperature,nucleationrateincreases duetoagreatabundanceofhydroxylionsandraisedtemperature.Theincreasein

formationofAgNPsisfollowedbyanincreaseinthekineticsofthedepositionof thesilveratoms(Correa-Llantenetal. 2013).Thewholecellsof Geotrichum candidum exposedtotetrachloroauricacidataconcentrationof1mMwasadded toresuspendedwholecells,andthencultureﬂaskswereincubatedinashakerat differenttemperaturesintherangeof15–40 CtoformAuNPs.Anincreasein reactionrateuptoacertainvaluewasobservedwithincreaseinreactiontemperaturewhichfurtherstarteddecreasing.Atemperatureof35 Cwasfoundtobe optimumforNPssynthesis,beyondwhichtheabsorptionat520nmdecreased.This maybeduetoinstabilityofreductivecompounds(protein/peptide)athigher temperatures(Mittaletal. 2013).

3.5IncubationTime

ThetimetakentocompleteNPsynthesisisanimportantparameterfroman industrialpointofview.Baietal.(2006, 2009)havenoticedthatthesizeofNPs increasesduetotheincreaseinincubationtimeduringtheformationofZnSand CdSNPsbyusingthebacterialspecies, Rhodopseudomonaspalustris and Rhodobactersphaeroides.DuringthesynthesisofCuNPsusingcellpelletorcellfreesupernatantof Pseudomonasﬂuorescens afterincubationwithCuSO4 solution, effectofincubationtimewasstudied.Itwasnoticedthatopticaldensity(absorbance)at610nmincreasedgraduallyupto90minandthendecreasedwhich revealedtheformationofCuONPs.Further,withanincreaseintime,sizereduction takesplace(ShantkritiandRani 2014).

4MechanismofNanocompoundFormationbyMicrobes

ThemechanismofsynthesisofNPsmediatedbymicrobesisdifferentforsynthesis bydifferentorganisms.AgeneralmechanismofformationofNPsisthat,ﬁrstlythe metalionsgotentrappedonthesurfaceorenterinsidethebacterialcells,andthen themetalionsarereducedtoNPsbythereleaseofcertainfactorsbymicrobeslike enzymesorproteins.Thispartmainlyfocusesonthepossibleactionofmechanism forsynthesisoftypicaltypesofNPs(AgNPs,AuNPs,CuNPs,MNPs,andQDs)by microbes.AdiagrammaticrepresentationofmechanisticactionofNPsisillustrated inFig. 1.

4.1MechanismfortheSynthesisofAgNPsbyBacteria

AlltheorganismsdonothavecapabilitytosynthesizeAgNPs.Asreportedearlier, thoseorganismswhichpossessthe“silverresistancemachinery”havethe

Optimization of various parameters (Temperature, pH, Incubation time, Growth Media and Bacterial Concentration)

Mechanism

Fig.1 Abriefrepresentationofmechanisticactionofmicrobe-mediatedgreensynthesisof nanocompounds

capabilityofAgNPssynthesiswhilethemechanismofresistancedifferswiththe organisms.Bacterialcellextractsmayserveasboththereducingandcapping agentsfortheformationofAgNPs.Thereductionofsilverionsbyvarious componentslikeenzymes/proteins,aminoacids,andpolysaccharidespresentin bacterialcellularextractsisfoundtobeeco-friendlybutchemicallycomplicated. Thepresenceofenzyme“nitratereductase”isresponsibleforthesynthesisof AgNPs.Itispostulatedthatnitratereductaseisthecausalagentbehindthesynthesis ofAgNPsin B.licheniformis.Nitratereductaseisinducedbynitrateionswhich reducesilverionstometallicsilver.NADH-andNADH-dependentnitratereductaseenzymesplayavitalroleforsynthesizingAgNPs. B.licheniformis secretesthe cofactorNADH-andNADH-dependentenzymes,especiallynitratereductase, whichmightberesponsibleforthereductionofAg+ toAg0 andthesubsequent formationofAgNPs(Husseinyetal. 2007).Moreover,inalkalinereactions,the synthesisofAgNPsisfasterascomparedtothereactioninacidicconditions. SynthesisofAgNPsincreasesasthepHofreactionmixtureisraisedtoward alkalinescaleandreachestomaximumatpH10.IfthereactionpHisincreased beyond10,thentheAgNPsynthesisstartsdeclining.Theproteinscontainingthiol groups( SH)bindwithsilverforminga–S–Agbond,responsibleforthesynthesis whichprovidesanideaabouttheconversionofAg+ toAg0.Inaddition,thealkaline

Bacteria Yeast Fungi

(Sources- food, soil, air, fruit and other biomass)

Culture + elemental metal (Ag, Au, Cu, Fe)

Greener synthesis of nanoparticles

ion(OH)isrequiredforthemetalionreduction.Undernormalconditions,it requiresgenerally4daysforthecompleteformationofsilverions,whereasless thananhouristakenwhenthepHismadealkaline.Alkalinityincreasesthe capacityoftheenzymeswhichplayaroleforAgNPsynthesis.

4.2MechanismofSynthesisofAuNPsbyMicrobes

AwidevarietyofmicrobesareknownfortheformationofAuNPs.Ageneral mechanismbehindthemicrobe-mediatedformationisthereductionofgold(Au+3) ionstoAg0 toformAuNPs.Ithasbeenspeculatedthattheenzymessecretedby variousmicrobeshelpinreductionofmetalions,causingnucleationandgrowthof NPs.ThesyntheticrouteofAuNPsinvolvesthereductionofgoldsaltsbyafew reducingagentsthathappeneitherintheextracellularorintracellularenvironment. Inastudyusingﬁlamentouscyanobacterium, Plectonemaboryanum UTEX485for thesynthesisofAuNPsshowedthatinabioticexperiments,thesolutionsofgold sulﬁdewerefoundtobestableforabout1monthat25 C,whereasAuNPsofsize 25nmhavingcuboctahedralshapewereprecipitatedat60–200 C.Similaristhe caseobservedwiththesolutionsofAuCl4 whichwerefoundtobestablefor 1monthat25–60 C,butathighertemperaturesof100–200 C,AuNPsofirregular shape( 25nm)wereformed.Increaseintemperaturefrom25 Cto60–200 C leadstoanincreaseinprecipitationofgold.Whenthebacterialcellswereexposed tohighconcentrationsofgoldsaltaqueoussolutionofgoldchloride,theyleadto theproductionorreleaseofmembranevesiclesfortheprotectionofcells.The interactionofvesiclecomponentslikeproteins,lipopolysaccharides,andphospholipidswiththegoldsaltsleadstotheprecipitationofgoldonthevesicularsurfaces orinsolutions(Lengkeetal. 2006).

ExtracellularsynthesisofAuNPformationiscommonlyreportedbyfungi F.oxysporum whichreleasesprotein-reducingagentsintothesolution.WhenAu3+ ionsfromgoldchloridesaltaretrappedandreducedbyproteinreductaseinthecell wall,theseproteinmoleculesbindtoAuNPsthroughthelinkagebetweentheamine groupsinaminoacidlysine(Mukherjeeetal. 2002).AuNPformationbyintracellular approachanddiffusionofAu3+ ionsfromthegoldsaltsolutiontakeplacethroughthe cellmembraneandarethenreducedbycystolicredoxmediators.Thedifferenttypes offunctionalgroupspresentonthecellsurfacelikecarboxyl,amine,phosphate,etc. providebindingsitesforAu(III)formineralizationofAu.Negativelychargedgold ionsbindonthepositivelychargedmyceliaof R.oryzae throughelectrostatic interactionwithphosphoproteins(Dasetal. 2012).However,itisstillunexplored whichneedextensiveresearchwhetherthediffusionofAu3+ ionsthroughthe membraneoccursviaactivebioaccumulationorpassivebiosorption.Thebiosorption mightbecausedbytoxicityofAu3+ ions,whichcanincreasetheporosityofthe microbialcellmembranes.

4.3MechanisticActionofMicrobialSynthesisofCuNPs

Differentspeciesofmicroorganismshavedifferentmechanisticactionforthe synthesisofCuNPs.Thebacteriataketargetmetalionsfromthesurroundingson theircellsurfaceorinsidethemembrane.Thecapturedmetalionsarereducedto NPsinthepresenceofreductantenzymesreleasedbythecellactivities.The interactionbetweenthepositivelychargedmetalionsandnegativelycharged carboxylatefunctionalgroupoftheenzymeslocatedinthecellwallcausesthe reductionofthemetalions(Lietal. 2011).Anotherstudyexplainstheformation processofCuNPnanoparticlein Serratia sp.Thebacterialcellsinstationaryphase faceanoxidativestressandosmoticstressbecauseoftheexhaustionofenergy sourceandincreaseofmetabolicwastes.Whenthecellsareexposedtohigh concentrationofmetalsalts,thestressisincreasedevenmore.Themetalsaltis internalizedintothecellmembrane,andCu2+ ionsgetreducedbyparticularbiomoleculestometallicCu,whichiscomparativelylesstoxicwhichfurtherleadto theproductionofCuNPs(Hasanetal. 2007).

4.4MechanismofMNPs

Themolecularmechanismofbacterialmagneticparticle(BacMP)biomineralizationisamultistepreaction(Arakakietal. 2008).First,thecytoplasmicmembrane invaginates,andthenthevesicleisproducedwhichactsasthestartingmaterialfor theformationoftheBacMPmembrane.AspeciﬁcGTPasehelpsintheprimingof theinvaginationforvesicleformationofmagnetotacticbacteriajustalikeother eukaryoticorganisms.Alongwithcytoskeletalﬁlaments,thevesiclesorganize themselvesinalinearchainstructure.Thenextstepofbiomineralizationincludes theaccumulationofFe3+ intothevesiclesbythetransmembraneirontransporters, transportproteins,andsiderophores.Feaccumulationisfurthercontrolledbya redoxsystem.Magnetitecrystalnucleationisthelaststepregulatedbyvarious proteinsrelatedwiththeBacMPmembraneformagnetitegeneration.Theseinclude theaccumulationofsupersaturatingironconcentrations,maintenanceofreductive conditionsandtheoxidationofirontoinducemineralization,orthepartialreductionanddehydrationofferrihydritetomagnetite(Arakakietal. 2008).

Anothermostfeasiblemechanismtakesintoconsiderationbothpassiveand activemechanismsforthemanufacturingofmagnetitesusing Shewanella oneidensis (Perez-Gonzalezetal. 2010).Firstly,byactivemechanism,theformationofFe2+ occurswhenbacterialspeciesmakeuseofferrihydriteasaterminal electronacceptor,andthepHinthecellsurroundingenvironmentincreasesmost likelyduetotheaminoacidmetabolism.Then,throughapassivemechanism,the localaccumulatedconcentrationofFe2+ andFe3+ atthenetnegativelychargedcell structuresandcellwallprovokesariseofsupersaturationofthesystemwithrespect tomagnetite,causingtheprecipitationofmagnetitetoformNPs.

4.5MechanismofSynthesisofQuantumDots

TheprecursormoleculeslikeCdCl2,Na2TeO3,mercaptosuccinicacid,andsodium borohydrideareincubatedwith E.coli inLBmedium.Theuniform-sizedCdTe QDscappedwithproteinsareformedwithgoodcrystallinityasaresultofmechanismofextracellulargrowthwhichencompassedthenucleationreactionofmetal ionswiththeproteinmoleculeyeastsecretedbybacteriaandthenfollowedby Ostwaldripening(Baoetal. 2010b).Itcouldbeassumedthat E.coli cells exposedtoextremeenvironmentalconditionsoftoxicheavymetalionsrequire startingofaspecifickindofdefensemechanismstoprotectthemfromtheunfavorablestressdevelopedbymetalion.Toovercomethemetalstress,thebacterial cellsgeneratemoremetal-bindingproteinswhichpromotethesynthesisofQDsby microbes.Moreresearchneedstobecarriedouttoconfirmthemechanismproposedabove.Inanotherreport,itwasdescribedthat S.cerevisiae yeastcellswere firstincubatedwithNa2SeO3 inasuitablegrowthmedia.Thentheharvested seleniumizedyeastcellswerefurtherculturedwithCdCl2-containingmedia whichresultedininsitusynthesisofCdSeQD.Glucancontentincreasesinthe cellwallsofyeastcellswhichresultinenhancedmechanicalstrength(Luoetal. 2014).

5Multi-scaleCharacterizationofNanocompounds

Thecharacterizationofbiosynthesizednanocompoundsisveryessentialasthe propertieslikesize,shape,surfacefunctionalgroups,thermalconductivity,and surfacechargeofNPsdeterminetheirbehaviorinthebodysystemswhichare requiredfortheirmedicalapplicability.Alargenumberofhigh-throughputinstrumentsareavailablewhichareusedforthecharacterizationofNPsofmicrobialmediatedsynthesis.Asthesize,shape,andotherpropertiesofNPsvarywiththe variationinreactionparameters,concentrationofprecursormoleculeused,typeof microbialcultureused,andthesynthesisroute,itisanecessarytasktodetermine thesepropertiesbeforetheuseofNPsfordifferentpurposes.Thecharacterization givesaprimaryclueaboutthebehaviorofNPsinthelivingsystems.Thefollowing characterizationtechniquesareusedtodeterminetheessentialcharacteristics ofNPs.

5.1ScanningElectronMicroscope(SEM)

SEMisusedtoestimatethesurfacetopographyofNPs.Anelectronbeamofhigh energystrikesthesamplesurfaceandtheninteractswiththeatomsatornearthe samplesurface.ThesignalsproducedbySEMincludesecondaryelectrons,

backscatteredelectrons,andcharacteristicX-rayswhichprovidedetailsaboutthe topographyandelementalcompositionofthesample(Joshietal. 2008).SEMcan beusedtoobserveonlytheexternalmorphologyofthesample.Thesample preparationofNPsiscomparativelysimpletoanalyzethesampleusingSEM. VanmathiSelviandSivakumar(2012)usedSEMtoestimatethesizeofAgNPs biosynthesizedby F.oxysporum. SEMmicrographsshowedthespherical-shaped AgNPsof20–25nm.

5.2TransmissionElectronMicroscope(TEM)

Abeamofelectroninteractswiththeinteriorofthesamplemainlythrough diffraction.Thelenses,deﬂectioncoils,andstigmatorshelpintheformationof imageandthenprojectitonthescreen.Theprojectionchamberhavingdifferent typesofelectrondetectorshelptorecordthesampleimages.Afocusedelectron beamwhenpassesthroughanextremelysmallthinsampleprovidesaninsightinto size,shape,composition,NPlocalization,crystallinity,andothercharacteristics (Punjabietal. 2015).TEMprovidestheinternalstructureofthesampleatavery highmagniﬁcationpower.TheonlylimitationofTEMislaboriousprocedureof samplepreparationandexpensive.TEMwasusedtocharacterizetheintracellular localizationandsizeofAuNPssynthesizedby Geobacillus sp.Thequasihexagonal-shapedAuNPsofsize5–50nmwereobserved(Correa-Llantenetal. 2013).

5.3AtomicForceMicroscope(AFM)

Thesamplesurfaceisscannedusingaprobeandtheoscillationamplitudeisusedto measurethesurfacecharacteristicsofthesample(Joshietal. 2008).AFMprovides thethreedimensionalstructuresoftheNPs.Itprovideshigherresolutionas comparedtoSEM.Insteadofusinghigh-energyelectronbeam,alaserlightis usedtomeasurethedeﬂectionofcantileverprobe.Inastudy,AFMwasusedto studytheinﬂuenceof Microbacteriumhominis and Bacilluslicheniformis extracellularpolymersonAgNPsandironoxideNPswhichrevealedthattheformed AgNPswereofsizelessthan100nm,whereasironoxideNPswereof100–200nm (Gholampooretal. 2015).

5.4DynamicLightScattering(DLS)

DLSisatechniquewhichisusedfordeterminingthesizeofparticlesinthe submicronregion.TheprincipleisbasedontheBrownianmotionofparticles

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THE CAMBRIDGE NATURAL HISTORY

EDITED BY

S. F. HARMER, Sc.D., F.R.S., Fellow of King’s College, Cambridge; Keeper of the Department of Zoology in the British Museum (Natural History) AND

A. E. SHIPLEY, M.A., Fellow and Tutor of Christ’s College, Cambridge; Reader in Zoology in the University

VOLUME IV

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CRUSTACEA

By G S, M.A. (Oxon.), Fellow of New College, Oxford; and the late W. F. R. W, M.A. (D.Sc., Oxon.), formerly Fellow of St. John’s College, Cambridge, and Linacre Professor of Human and Comparative Anatomy, Oxford

TRILOBITES

By H W, M.A., St. John’s College, Cambridge; University Lecturer in Palaeozoology

INTRODUCTION TO ARACHNIDA, AND KINGCRABS

By A. E. S, M.A., F.R.S., Fellow and Tutor of Christ’s College, Cambridge; Reader in Zoology

EURYPTERIDA

By H W, M.A., St. John’s College, Cambridge; University Lecturer in Palaeozoology

SCORPIONS, SPIDERS, MITES, TICKS, ETC.

By C W, M.A., Christ’s College, Cambridge; Zoologist to the Royal Agricultural Society

TARDIGRADA (WATER-BEARS)

By A. E. S, M.A., F.R.S., Fellow and Tutor of Christ’s College, Cambridge; Reader in Zoology

PENTASTOMIDA

By A. E. S, M.A., F.R.S., Fellow and Tutor of Christ’s College, Cambridge; Reader in Zoology

PYCNOGONIDA

By D’A W. T, C.B., M.A., Trinity College, Cambridge; Professor of Natural History in University College, Dundee

1909

All the ingenious men, and all the scientific men, and all the fanciful men, in the world, with all the old German bogypainters into the bargain, could never invent ... anything so curious, and so ridiculous, as a lobster.

C K, The Water-Babies.

For, Spider, thou art like the poet poor, Whom thou hast help’d in song. Both busily, our needful food to win, We work, as Nature taught, with ceaseless pains, Thy bowels thou dost spin, I spin my brains.

S, To a Spider.

Last o ’ er the field the Mite enormous swims, Swells his red heart, and writhes his giant limbs.

E D, The Temple of Nature.

PREFACE

The Editors feel that they owe an apology and some explanation to the readers of The Cambridge Natural History for the delay which has occurred in the issue of this, the fourth in proper order, but the last to appear of the ten volumes which compose the work. The delay has been due principally to the untimely death of Professor W. F. E. Weldon, who had undertaken to write the Section on the Crustacea. The Chapter on the Branchiopoda is all he actually left ready for publication, but it gives an indication of the thorough way in which he had intended to treat his subject. He had, however, superintended the preparation of a number of beautiful illustrations, which show that he had determined to use, in the main, first-hand knowledge. Many of these figures have been incorporated in the article by Mr. Geoffrey Smith, to whom the Editors wish to express their thanks for taking up, almost at a moment’s notice, the task which had dropped from his teacher’s hand.

A further apology is due to the other contributors to this volume. Their contributions have been in type for many years, and owing to the inevitable delays indicated above they have been called upon to make old articles new, ever an ungrateful labour.

The appearance of this volume completes the work the Editors embarked on some sixteen years ago. It coincides with the cessation of an almost daily intercourse since the time when they “came up” to Cambridge as freshmen in 1880.

S. F. H. A. E. S.

March 1909.

S C V

CRUSTACEA

CHAPTER I

CRUSTACEA

G O 3

CHAPTER II

CRUSTACEA (continued)

E B P C W 18

CHAPTER III

CRUSTACEA ENTOMOSTRACA (continued)

C 55

CHAPTER IV

CRUSTACEA ENTOMOSTRACA (continued)

CHAPTER V

CRUSTACEA (continued)

M: L P: E: S A: P M C

I A: H S

110

CHAPTER VI

CRUSTACEA MALACOSTRACA (continued)

E (CONTINUED): E E

C E D

144

CHAPTER VII

CRUSTACEA (continued)

R D M F-

197

CHAPTER VIII

CRUSTACEA (continued)

T 221

ARACHNIDA

CHAPTER IX

A I

CHAPTER X

ARACHNIDA (continued)

D = M X 259

CHAPTER XI

ARACHNIDA DELOBRANCHIATA (continued)

E = G 283

CHAPTER XII

ARACHNIDA (continued)

E S P 297

CHAPTER XIII