the british empire ecology and famines in late 19th century central india

... throughout the years due to the inconsistent supplies from the Philippines. On the other hand, spiny lobster landings in Kota Kinabalu were small, accounting for only 2% of the 2002 landings. There ... transported mainly from northern central provinces such as Hue, Da Nang, Quang Nam, Quang Ngai and Binh Dinh to meet the demand in southern central provinces, including Phu Yen, Khanh Hoa and Ninh ... Park and Pulau Tiga Park on the west coast and the Selingan Turtle Islands on the northeast. On the other Status of Spiny Lobster Resources in Sabah, Malaysia Rooney Biusing and Chio Fui Lin Department...

... allergies in the United States and a 29% higher risk of respiratory problems in the US compared to England. Since England includes hay fever in allergies and the US in respiratory, the relative ... ‘explanation’ of the excess disease in the US arises from the inclusion in the model of the indicators of prevalence of the specific childhood illnesses themselves as opposed to the interactions of these ... country variations in social integration and social interactions explain differences in life expectancy in industrialized countries? In E. Crimmins, S. Preston, and B. Cohen (eds.), International...

... and even sister Lily served by entertaining the troops with her singing. A propaganda poster circulated all over England featuring the “Fighting Macks,” with pictures of all the brothers in ... the brothers in uniform—including Fred, the brother who was killed— and also including Lily and their mother. One of the brothers enlisted at the age of thirteen, and another at fourteen. George ... uniforms were in fashion during the 1930s, and these riding clubs were just good opportunities to socialize and get drunk. There is certainly fodder for some closer scrutiny of the in- triguing issue...

... proposed in systems involving phenoloxidase enzymes. The deamination of amino acids, such as serine, phenylalanine, proline, methionine, and cysteine by birnessite, and the role of pyrogallol in influencing ... mechanical, including photocopying, microfilming, and recording, or by any informa- tion storage and retrieval system, without permission in writing from the publisher. Current printing (last digit): 10987654321 PRINTED ... in uencing their mineralization have been investigated (152,153). Nitrogen mineralization was inhibited by pyrogallol, whereas S mineralization of S-containing amino acids was not, except in the...

... Currently,itisevidentthatmicroorganismsformcomplexmicrobialfoodwebsin allaquaticecosystems,andthattheiractivitiesandmetabolismsoftenaretightlycoupled and/ ormutuallyaffected(132,143,144).Therefore,itisnotsurprisingthatenzymatic propertiesandactivitiesofdifferentcomponentscreatingthemicrobialfoodwebsinlake ecosystemshavedemonstratedcloserelationships.Severalreportshavedocumentedthe strongdependencyofbacterialsecondaryproductiononectoenzymeactivitiesofaquatic microorganisms(2–4,16,17,19,25,28,29,33,36,59).Thereoftenisasignificantcorrelation betweenphytoplanktonprimaryproductionandactivitiesofdifferentectoenzymesin freshwaterecosystems(25,28,29,33,52). Ourstudiesinlakesofdifferingdegreesofeutrophicationhaveshownmicrobial esteraseactivitytobepositivelycorrelatedtophytoplanktonprimaryproduction,bacterial secondaryproduction,andconcentrationofdissolvedorganiccarbon(DOC)(Fig.13). Wehavefoundasignificantnegativerelationshipbetweenenzymeactivityandtheper- centageofphytoplanktonextracellularrelease(PER)ofphotosyntheticorganiccarbonin thestudiedlakes.ThisnegativecorrelationbetweenPERandesteraseactivityindicated thatenzymesynthesiswaspartiallyinhibitedinbacteriabylow-molecular-weightphoto- syntheticproductsofphytoplanktonthatwerereadilyutilizedbythesemicroheterotrophs: i.e.,catabolicrepressionofesterasesynthesiswasfoundinlakescharacterizedbyhigh PERofphytoplankton(29,33). VIII.ECTOENZYMEACTIVITYANDLAKEWATEREUTROPHICATION Theimportanceoforganicmatterasavariableforevaluatingthetrophicstatusoflakes hasbeenrecognizedsincethebeginningofthe20thcentury(145,146).Increasingconcen- trationsoforganicconstituentsinwaterarethedistinctindicatorsofacceleratedeutrophi- cationprocessesinmanylakes(147–149).Ourstudiesclearlydemonstratedthatenzyme activitiesweresignificantlypositivelyproportionaltoDOCcontentoflakes(Fig.13C). Asdescribedearlierinthischapter,severalmicrobialectoenzymesareresponsiblefor rapidtransformationanddegradationofbothdissolvedorganicmatterandPOMinfresh- waterecosystems.Therefore,wehypothesizethatan‘‘enzymaticapproach’’canbevery usefulinthestudiesoflakeeutrophication. Severalreportspointedoutthatmicrobialenzymaticactivitieswerecloselyrelated totheindicesofwatereutrophicationand/orthetrophicstatusofaquaticecosystems (25,27,29,31,33,38,52,58,62,78).Ourstudiesalongthetrophicgradientoflakes(from oligo/mesotrophictohypereutrophiclakes[Fig.14A]supportourhypothesis(andthe assumptionsofothers)thatselectedenzymaticmicrobialactivitiesareverypracticalfor arapidrecognitionofthecurrenttrophicstatusoflakes.Activitiesofalkalinephosphatase, esterase,andaminopeptidaseincreasedexponentiallyalongatrophicgradientandcorre- latedsignificantlywiththetrophicstateindexofthestudiedlakes(Fig.14B,C,D).We alsofoundastrongrelationshipbetweenactivitiesofectoenzymesandphytoplankton primaryproductionintheselakes.Rapidincreasesinectoenzymeactivitieswereobserved especiallyinarangeofgraduallyeutrophiclakeswhenthevalueofCarlson’strophic stateindex(TSI)wasabove55(150)(Fig.14). Moreover, ... lakewater.Figures2Band2CshowthatectoenzymesynthesisinDOM-enrichedsamples wasnolongerrepressedwhentheconcentrationofthereadilyutilizablelowmolecular- weightmoleculesfellbelowacriticallevel,andpolymericsubstrateshadtobeusedto supportthegrowthandmetabolismofbacteria.Similarinsituobservationsduringphyto- planktonbloomdevelopmentandbreakdownwerereportedfor-glucosidaseactivityin eutrophicLakePluòsee(24),for-glucosidaseandaminopeptidaseactivitiesinmeso- trophicLakeScho ă hsee(25),andforlipaseactivityineutrophicLakeMikoajskie(40). Despitethewidespreadoccurrenceofcatabolicrepression,withtheexceptionof thoseforentericbacteria,themoleculardetailsoftherepressionarepoorlyunderstood. Somestudieshaveindicatedthatcyclicadenosinemonophosphate(cAMP),togetherwith itsreceptorprotein,mayplayacentralroleincontrolofcatabolicrepression(41,42). Usingtherepressionstrategyforectoenzymesynthesis,microorganismscanavoidthe wastefulproductionofinducibleenzymes,whicharenotusefulwhentheirgrowthisnot limitedbyUDOM(3,19,24,35). B.InhibitionofActivity Itisimportanttoconsiderthattherepression/derepressionofanectoenzymenotbe equatedtothereversibleinhibitionofactivity.Evenifanectoenzymeissynthesized,its activitymaybeinhibitedbytheaccumulationoftheendproductorbyhighconcentrations ofthesubstrate(19).Twogeneraltypesofreversibleinhibitionareknown:competitive andnoncompetitiveinhibition. Competitiveinhibitionoccurswhenaninhibitingcompoundisstructurallysimilar tothenaturalsubstrateand,bymimicry,bindstotheenzyme.Indoingso,itcompetes withanenzymesnaturalsubstratefortheactivesubstrate-bindingsite.Thehallmarkof competitiveinhibitionofmanyectoenzymes(e.g.,alkalinephosphatase,-glucosidase, aminopeptidase)isthatitdecreasestheafnityofanectoenzyme(anincreaseofthe apparentMichaelisconstantisobserved)forthesubstrateand,therefore,inhibitstheinitial velocityofthereaction(Fig.3)(13,26,37).Competitiveinhibitionisreversibleandcan beovercomebyincreasedsubstrateconcentration,andthereforethemaximumvelocity (V max )ofthereactionisunchanged(Fig.3A). Noncompetitive ... lakewater.Figures2Band2CshowthatectoenzymesynthesisinDOM-enrichedsamples wasnolongerrepressedwhentheconcentrationofthereadilyutilizablelowmolecular- weightmoleculesfellbelowacriticallevel,andpolymericsubstrateshadtobeusedto supportthegrowthandmetabolismofbacteria.Similarinsituobservationsduringphyto- planktonbloomdevelopmentandbreakdownwerereportedfor-glucosidaseactivityin eutrophicLakePluòsee(24),for-glucosidaseandaminopeptidaseactivitiesinmeso- trophicLakeScho ă hsee(25),andforlipaseactivityineutrophicLakeMikoajskie(40). Despitethewidespreadoccurrenceofcatabolicrepression,withtheexceptionof thoseforentericbacteria,themoleculardetailsoftherepressionarepoorlyunderstood. Somestudieshaveindicatedthatcyclicadenosinemonophosphate(cAMP),togetherwith itsreceptorprotein,mayplayacentralroleincontrolofcatabolicrepression(41,42). Usingtherepressionstrategyforectoenzymesynthesis,microorganismscanavoidthe wastefulproductionofinducibleenzymes,whicharenotusefulwhentheirgrowthisnot limitedbyUDOM(3,19,24,35). B.InhibitionofActivity Itisimportanttoconsiderthattherepression/derepressionofanectoenzymenotbe equatedtothereversibleinhibitionofactivity.Evenifanectoenzymeissynthesized,its activitymaybeinhibitedbytheaccumulationoftheendproductorbyhighconcentrations ofthesubstrate(19).Twogeneraltypesofreversibleinhibitionareknown:competitive andnoncompetitiveinhibition. Competitiveinhibitionoccurswhenaninhibitingcompoundisstructurallysimilar tothenaturalsubstrateand,bymimicry,bindstotheenzyme.Indoingso,itcompetes withanenzymesnaturalsubstratefortheactivesubstrate-bindingsite.Thehallmarkof competitiveinhibitionofmanyectoenzymes(e.g.,alkalinephosphatase,-glucosidase, aminopeptidase)isthatitdecreasestheafnityofanectoenzyme(anincreaseofthe apparentMichaelisconstantisobserved)forthesubstrateand,therefore,inhibitstheinitial velocityofthereaction(Fig.3)(13,26,37).Competitiveinhibitionisreversibleandcan beovercomebyincreasedsubstrateconcentration,andthereforethemaximumvelocity (V max )ofthereactionisunchanged(Fig.3A). Noncompetitive...

... Investigationsofextracellularenzymesfrommarineanimalsandenzymesisolatedfrom prokaryotesareconsideredonlyifaclearconnectiontomarineecologyisestablished. Thetermextracellularenzymesisusedthroughoutthischapter,whereasChro st(5)distin- guishesbetweenectoenzymesandextracellularenzymes.Ectoenzymesaredenedby Chro st(5)andinChapter2asenzymeslocatedintheperiplasmicspaceorattachedto theoutermembraneofthebacterialcell.Extracellularenzymesareenzymesfreelydis- solvedinthewaterorattachedtoparticlesotherthantheenzyme-synthesizingcell .In thischapter,however,thetermextracellularenzymesreferstobothectoenzymesand extracellularenzymes,unlessotherwisestated. Earlystudiesonthefateoforganicaggregatesanddissolvedpolymersinthesea werepresentedbyRiley(6),Walsh(7),andKhailovandFinenko(8).Overbeck(9)re- viewedtheearlystudiesonextracellularenzymeactivityintheaquaticenvironment. II.ECOLOGICALPRINCIPLESOFENZYMATICPATTERNS INTHESEA A.TheConceptoftheMicrobialLoopandtheRoleofExtracellular Enzymes Themicrobialloop(10)encompassesthecombinedactivitiesofautotrophicandheterotro- phiceukaryoticaswellasprokaryoticorganismssmallerthan20àm.Theseorgan- isms,representedbybacteria,nanoagellates,ciliates,andphototrophicprochlorophytes, aswellascyanobacteria,formafoodweboftheirown,looselyconnectedtothefood webofthelargergrazers.Ingeneral,thenutritionalbasisofthemicrobialfoodwebis providedbythepoolofdissolvedorganicmatter(DOM)andparticulateorganicmatter (POM).TheDOMpoolisapriorireservedforbacterialutilization,whereascompetition withmetazoansoccursforPOM.Thiscompetitionisdeterminedbythebacterialpotential forenzymaticdissolutionofPOMontheonehandandthefeedingactivityofthemetazo- ansontheotherhand.Thebulkofboththedissolvedandparticulateresources,however, requiresenzymatichydrolysispriortouptakebybacteria(Fig.1).Thustheenzymatic activitiesofbacteriainitiateorganiccarbon(C)remineralizationanddenethetypeand quantityofsubstrateavailabletothetotalmicrobialfoodweband,tocertainextent,also tothetoppredatorsinthesystem. B.FreeandAttachedEnzymeActivity Generally,extracellularenzymesmaybeboundtothecell(denedasectoenzymesby Chro st[5])orinthefreeandadsorbedstate(11,12).Mostofthetotalenzymeactivity inseawaterhasbeenfoundtobeassociatedwiththeparticlesizeclassdominatedby bacteria(0.2àm3àm)(13,14)(Table1).Dissolvedenzymes(15)andlargeparticles 8 ... environment. In the salinity gradient between the Sac- ramento River and the central San Francisco Bay, increasing salinity was positively corre- lated with aminopeptidase activity and negatively correlated ... inthefreeform,andconsequentlyavailableforrapiduptake,remainsunknown.This adsorptionandtheconcurrentloweravailabilityforbacterialuptakemightcauseanunder- estimationoftheactualbacterialproductiononandinpolysaccharide-richmaterialsuch asmarinesnow(44),relativetobacterialenzymeactivity. ThecouplingbetweenhydrolysisanduptakeofDOMinparticle-associatedandfree bacteriaisstillnotfullyunderstood.Thereasonswhytheattachedbacteriabenetsolittle fromtheirstronghydrolyticactivities,iftherearenolimitingfactorsinterferingwiththe uptakeofenzymatichydrolysisproducts,areunknown.Thisfundamentaldiscrepancy shouldbemorethoroughlyinvestigatedinordertoimproveunderstandingofthebiogeo- chemicaluxoforganicmatterandtheroleofbacteriainthecyclingofDOMintheocean. Inanycase,itiswellacceptedthatparticledecomposition(45)contributessignicantlyto thelossoforganicmaterialfromsettlingparticlesduringsinkingandthusdeterminesthe efciencyofthebiologicalCpump(organicmattertransportfromtheseasurfacetothe seabed). D.EnvironmentalFactorsInuencingEnzymaticActivity Themagnitudeofthemainextracellularenzymeactivitiesinmarinewaterisfrequently intheorderaminopeptidasephosphatase-glucosidasechitobiaseesterase -glucosidase.However,exceptionsmayoccur,asobservedbyChristianandKarl(46) intheequatorialPacic,where-glucosidasewasaboutfourtimeshigherthanaminopep- tidase.Thissuggeststhattheremaybefactorsregulatingactivitiesonalargescale.How- ever,knowledgeofglobalregulatingfactorsisscarce.ChristianandKarl(47)foundthat histidineandphenylalanineinhibitedaminopeptidaseexpressioninAntarcticwaters.Like- wise,KimandLipscomb(48)suggestedthatmetalsmayberegulatingfactorsforproteases (leucineaminopeptidaseseemstobeprincipallyaZn 2 -dependentenzyme).Thiswas especiallyduetoZn 2 (whichisrareinmarinewaters),butMn 2 ,Co 2 ,Fe 2 ,andMg 2 mightalsoplayarole(4750).Inthesurfacelayeroftheocean,ultraviolet-Bradiation canbeimportant,mainlythroughphotochemicaldegradationoftheextracellularenzymes (51,52).Withrespecttophosphataseactivity,theabundanceofinorganicPisregardedas aregulatingfactor,particularlyfortheP-limitedregionsintheoceans(5355).However, dissolvedorganicphosphorus(DOP)andparticulateorganicPalsoshouldbeconsidered (56).Furthermore,mechanismsofphosphataseregulationaredifferentforbacteriaand phytoplankton.Whilethephosphatasesofphytoplanktonseemtoberegulatedstrictly byinorganicPconcentrations(49,5759),thismechanismisnotsoclearforbacterial phosphatases.ThelattermaytargetCandNratherthanPsupply,aspointedoutforthe limneticenvironmentbySiudaandGu ă de(60)andforthedeepandC-limited,butphos- phate-replete,oceanbyHoppeandUllrich(61).Inanycase,regardlessofenvironmental factors,variationofspeciescompositionwithinthebacterialcommunitycansignicantly inuencethedistributionofenzymeactivitiesinthesea(62,63). Theeffectsofenvironmentalfactorsonenzymeregulationarereectedbythediver- sityofextracellularenzymes,asexpressedinthepossiblerangesofK m andthepatterns ofindividualcell-specicenzymepotentials(Table2,Table3).InformationontheK m values...

... Althoughthisstudyinvolvedtheuseofageneticallymodifiedmicrobe,themodifi- cationswerenotintendedtohaveafunctionalimpact;theywereinsertedasgeneticmark- ers.Asecondstudycomparingtheeffectofthesamegeneticallymarkedstraintothatof afunctionallymodifiedstrainshowedeffectsthataremoreinteresting(36).Theaimof thisworkwastodeterminetheimpactintherhizosphereofwildtypealongwithfunction- allyandnonfunctionallymodifiedPseudomonasfluorescensstrains.Thewild-typeF113 straincarriedageneencodingtheproductionoftheantibiotic2,4-diacetylphloroglucinol (DAPG),usefulinplantdiseasecontrol,andwasmarkedwithalacZYgenecassette .The firstmodifiedstrainwasafunctionalmodificationofstrainF113withrepressedproduction ofDAPG,creatingtheDAPGnegativestrainF113G22.Thesecondpairedcomparison wasanonfunctionalmodificationofwild-type(unmarked)strainSBW25,constructedto carrymarkergenesonly,creatingstrainSBW25EeZY-6KX. Significantperturbationswererecordedintheindigenousbacterialpopulationstruc- ture;theF113(DAPGϩ)straincausedashifttowardslower-growingcolonies(Kstrate- gists)comparedwiththenon-antibiotic-producingderivative(F113G22)andSBW25 strains.TheDAPGϩstrainalsosignificantlyreduced,incomparisonwiththoseofthe otherinocula,thetotalPseudomonassp.populations,butdidnotaffectthetotalmicrobial populations.ThesurvivalofF113andF113G22wasanorderofmagnitudelowerthan thatoftheSBW25strains.TheDAPGϩstraincausedasignificantdecreaseintheshoot- to-rootratioincomparisontothatofthecontrolandotherinoculants,indicatingplant stress.F113increasedsoilalkalinephosphatase,phosphodiesterase,andarylsulfataseac- tivities(Table2)comparedtothoseofthecontrols.Theotherinoculareducedthesame enzyme ... beensteadyprogressinourunderstanding ofthe rhizosphereduringthelast 100yearsandanincreasingrealizationthatitcanhavemany in uencesoncrop productivity(Table1).However,therehasbeen a sudden increase in interest and ... Theresultsshowedlargedifferencesbetweenthe2daysofsamplinginsoilenzyme activities(e.g.,alkalinephosphatase,Fig.2)andavailablesoilnutrients(e.g.,nitrate,Fig. 3).Differenceswerefoundalsobetweenthevariousoilseedrapevarietieswithmostsoil enzymesmeasuredandwiththeavailablesoilnutrients.However,therewaslittlediffer- encebetweentheenzymeactivitiesintherhizosphereoftheGMandnon-GMplants. Themajorfactorinfluencingtheenzymeactivitiesandsoilnutrientsbetweenthetwo samplingdayswasthesoilmoisturecontent,whichwasincreasedbyovernightrain. Therefore,inthisfieldtrial,thedifferencesbetweensoilenzymeactivitieswerenotattrib- utabletoplantgeneticmodification,buttoenvironmentalvariationandtodifferencesin plantvariety. V.CONCLUSIONS Clearlyenzymeactivitiesareusefulindeterminingperturbationsinthesoilenvironment broughtaboutbychangesinagriculturalpractices,theuseofagrochemicals,pollution events,ortheexploitationofgeneticallymodifiedorganisms.Biocontrolofpestsand diseasesisameansbywhichenzymefunctionhasbeenexploited(43),butthereiseven greateropportunitytomonitorandmanipulateenzymesasgenerationsofplantnutrients, plant-growth-promotingagents,soilstructurestimulants,andbioremediationcatalysts. Althoughbioremediationhashadlessattentionthanbiocontrol,thepotentialfor exploitationisenormous(44).Mostresearchhasbeenfocusedonmicrobialinoculants (bioaugmentation),butitisequallyrelevanttoconsiderhowtooptimizethefunctionof theindigenousorganisms(biostimulation).Phytoremediation,byplantrootsthemselvesor associatedmicrobiota(rhizoremediation),isbecominganincreasinglyinterestingcleanup solutionforsoils.Mostattentionhasbeenpaidtoheavymetaldecontamination ,and whereasthereisinevitablysomeenzymeinvolvement,littlehasbeencharacterized.How- ever,rhizospheremicroorganismsproduceenzymesthathavethecapacitytocatabolize awiderangeoforganicpollutants.Microbialdehalogenationisdescribedindetailin Chapters1 8and1 9,butofspecialinterestarehydrogencyanideandothernitriles.Not only...

... delivered to the apoplast by the host cell. Then sucrose is hydrolyzed in the apoplastic interface by an acid invertase of plant origin, and the resulting hexoses are absorbed by the fungus (59), and ... 4)-glucans(53).Xyloglucansare-1,4-glucanswithsidechainsthatcanhydrogenbond tocellulosemicrobrils,cross-linkingthemandrestrainingcellexpansion.Inadditionto astructuralrole,xyloglucanscanbehydrolyzedbyhydrolyticenzymes,andtheoligosac- charidesproducedmayactassignalmolecules(15,54). Theplantcellwallcontainsglucanasesandglycosidasesthathydrolyzexyloglucan intomonosaccharides.Endo--1,4-glucanaseactivityisresponsiblefortherststepof degradationwherebythexyloglucanisendohydrolyzedintolargefragmentsandexo-1,4- glucanaseactivityliberateslow-molecular-weightfractionsfromtheendsoflongpolysac- charidechains(41).Theproductionofhemicellulolyticenzymeshasbeenobservednot onlyinparasitesbutalsoinmutualisticmicroorganismssuchasRhizobiumspecies(24) andarbuscularmycorrhiza(28). Endoxyloglucanaseactivityincreasesduringgrowthanddevelopmentofroots(55). Thisactivitywasconsistentlyhigheratthebeginningofcolonizationandthelogarithmic stageofdevelopmentofmycorrhizalfungus(55).Theincreaseinfungalstructuresthat penetratethecellwallduringthelogarithmicstageofrootcolonizationmayexplainthe increaseinthedifferentactivitiesatthistime(56).Theevolutionofendoxyloglucanase activitiesinplantsparalleledthechangesintheexternalmycelium.Therewere,however, bandsofxyloglucanaseactivityinnonmycorrhizalrootsthatwereabsentinmycorrhizal roots;thatmaysuggestqualitativeinhibitionbythefungusofsomeplantactivity.Inhibi- tionofplantproteinsynthesisbyAMfungihasbeenobservedinseveralplantAMfungi associations(57,58). III.ENZYMESINTHEPHYSIOLOGYOFTHEASSOCIATION A.PhosphorusUptake Itnowisestablishedthatmycorrhizalcolonizationcanenhancetheuptakefromsoilof solubleinorganicPbyplantroots(59).Althoughparticularlyimportantinlow-Psoils, anincreasedrateofPuptakecanoccuroverarangeofsoilPlevelsevenwhenmycorrhizal growthresponsesnolongeroccur.TheenhancedPuptakebymycorrhizalplantsismost likelytheresultoftheexternalfungalhyphaesactingasanextensionoftherootsystem, therebyprovidingamoreefcient(moreextensiveandbetterdistributed)absorbingsur- faceforuptakeofnutrientsfromthesoilandfortranslocationtothehostroot(60).External hyphaeofAMfungimustabsorborthophosphate(Pi)byactivetransport(59,61).They haveanactiveH -ATPaseintheplasmamembranethatwouldbecapableofgenerating therequiredproton-motiveforcetodriveH -phosphatecotransport,andPcertainlyis accumulatedtohighconcentration(62). Polyphosphate(poly-P)isamajorPreserveinmanyfungianditaccumulatesin vacuolesofAMfungi(63).Transferofmycorrhizalrootsfromlow-tohigh-Pmedia resultsinarapidaccumulationofpoly-P(64).Enzymesofpoly-Psynthesishavebeen foundinmycorrhizaltissue(63,65).Polyphosphatekinase,whichcatalyzesthetransfer oftheterminalphosphatefromATPtopoly-P,wasdetectedinbothexternalhyphaeand mycorrhizalrootsbutnotinuninfectedroots,indicatingthatpoly-Pcanbesynthesized onlybythefungalcomponentofthemycorrhiza. AlthoughitnowseemslikelythatPistranslocatedbyprotoplasmicstreaminginto theintraradicalhyphaeaspoly-P(66),littleisyetknownofthebiochemicalmechanisms involved.Thetransportthroughthehyphaeandunloadingstepswithinthearbusculemay belinkedtopoly-Pmetabolism(Fig.2).Highproportionoflong-chainpoly-Ptototal Copyright ... ThepatternsofenzymeactivityandmRNAaccumulationsuggestthatchitinases and -1,3-glucanasesmightbepartoftheearlydefenseresponsebytheplanttotheinvad- ingfungus,whichisthensuppressedassymbioticinteractionsdevelop.Inthiscontext, planthydrolasesmaybeinvolvedintheregulationofAMdevelopment.Nevertheless, someexperimentaldatarevealedthatitisnotlikelythatplantchitinasesandglucanases areessentialtothecontrolofthegrowthofAMfungi.Transgenicplantsconstitutively expressinghighlevelsofdifferentacidicformsoftobaccoPRs(includingchitinasesand β-1,3-glucanases)becamenormallycolonizedbytheAMfungi(122,123).Thefactthat chitinasesandβ-1,3-glucanasesinducedbytheAMsymbioticfungiorbyconstitutive geneexpression,donotpreventrootcolonizationsuggeststhattheyareineffectivein controllingfungaldevelopment.ThelowenzymaticaffinityforAMfungalcomponents orinaccessibilityoftheseenzymestofungalcellwallcomponentsmaycausethisineffec- tiveness(112). Conversely,specificacidicformsofchitinaseandβ-1,3-glucanaseareactivatedin severalplantscolonizedbyAMfungi.Thesesymbiotic,specificisoenzymeshavebeen reportedinpea(124),tobacco(118),andtomato(125–127)rootsandaredifferentfrom pathogen-inducedisoformsorconstitutiveenzymes.Inaddition,newchitosanaseisoforms havebeenshowninpea(128)andtomato(126).Chitosanasesarehydrolyticenzymes actingonchitosan,aderivativepartiallyorfullydeacetylatedofchitin(129).Interestingly, themycorrhizal-relatedchitinaseisoformdescribedintomato-colonizedrootsappearedto displaychitosanaseactivity.Thisbifunctionalcharacterwasnotfoundfortheconstitutive enzymes,orinPhytophthorasp.–inducedchitinases(126).Mycorrhizal-specificplantchi- tinasesarenotactiveinpathogen-infectedroots(118,124–125)orinRhizobiumsp.legume symbiosis(130),indicatingadifferentialinductionandfunction. Althoughtheprecisefunctionofplanthydrolaseactivitiesintheestablishmentof AMsymbioticinteractionisstillunclear,theirstimulationseemstobeakeypointinthe mechanismofrecognitionandsignalingbetweenplantrootsandAMfungi.Aregulatory roleoftheseenzymesduringestablishmentofAMandotherrootsymbiosishasbeen proposed.Stimulationofspecificplantchitinaseshasbeenreportedinsoybean/Rhizobium sp.(131)andectomycorrhiza(132).Ithasbeenpostulatedthatchitinasesmaybeinvolved intherecognitionoftherhizobialnodulationsignalsand,thus,intheregulationofthe nodulationprocess(133).Thedatasuggestaspecificrolefortheseenzymes,onethat couldberelatedintheAMsymbiosistothedetection,modification ,and/ orreleaseof chitinorchitosanoligomersfromthefungalcellwallthatcanactassignalingcompounds duringthedevelopmentofAM(Fig.3).Inthisprocessofsignalexchange,themodulation of...

... 2.Glucanases β-1,3-glucan,orlaminarin,isapolymerofd-glucoseinaβ-1,3configuration,arranged ashelicalcoils.Fungalcellwallscontainmorethan60%laminarin.Whereaschitinis arrangedinregularlyorderedlayers,laminarinfibrilsarearrangedinanamorphicmanner. Therearechemicalbondsbetweenthelaminarinandchitin,andtogethertheyforma complexnetofglucanandGlcNAcoligomers(103).Laminarinishydrolyzedmainlybyβ- 1,3-glucanases,alsoknownaslaminarinases.Theseenzymes,describedinfungi,bacteria, actinomycetes,algae,mollusks,andhigherplants,arefurtherclassifiedasexo-andendo- β-glucanases.Exo-β-1,3-glucanases(β-1,3-glucanglucanohydrolase,[EC3.2.1.58])hy- drolyzelaminarinbysequentiallycleavingglucoseresiduesfromthenonreducingendsof polymersoroligomers.Consequently,thesolehydrolysisproductsareglucosemonomers. Endo-β-1,3-glucanases(β-1,3-glucanglucanohydrolase[EC3.2.1.6orEC3.2.1.39]) cleaveβ-1,3linkagesatrandomsitesalongthepolysaccharidechain,releasingsmaller oligosaccharides.Bothenzymetypesarenecessaryforthefulldigestionoflaminarin (104).Theseenzymeshaveseveralfunctionsinfungiincludingnutritioninsaprotropism, mobilizationofβ-glucansunderconditionsofC-andenergy-sourceexhaustion,anda physiologicalroleinmorphogeneticprocessesduringfungaldevelopmentanddifferentia- tion(105). Glucanaseshavebeensuggestedasanothergroupofkeyenzymesinvolvedinthe mycoparasitismofGliocladiumandTrichodermaspp.againstfungalplantpathogens(Ta- ble1).Thesubstrateoftheseenzymes,β-1,3-glucan,isoneofthemajorcomponentsof fungal ... against plant-pathogenic fungi. The free enzyme can be introduced into the irrigation water or incorporated into the seed coating to protect germinating seedlings. However, the activity of free enzymes in the soil ... expression in T. harzianum is regulated by (i) binding of Cre1 to two single sites in the ech42 promoter, (ii) binding of a ‘‘mycoparasitic’’ protein–protein complex to the ech42 promoter near the Cre1...

... affecting the efficiency of interaction of the substrate and enzyme molecules. In other words, a portion of the enzyme molecules existing in the field soil may not be actively engaged in catalyzing their ... enzymes, laccase and tyrosinase. The potential role of these enzymes in the humification of anilinic and phenolic compounds and reduction of their bioavilability with the passage of time (aging) is sufficient ... invertase, and protease have been found to be stimulated in the detritosphere (the soil litter interphase) (67). In another study, xylanase and invertase levels were ele- vated in the soil particle-size...

... wererepressedbyaddedN;formapleandoak,theseactivitiesincreased.Theresults suggestedthatwhiterotfungi,whichproduceligninasesinresponsetolowNavailability, weredisplacedbysupplementalN,slowingthedecompositionofrecalcitrantlitter. HenriksenandBreland(27)alsofocusedontheroleofNinthedecomposition process.Usingamicrocosmsystemofwheatstrawandsoil,theyfoundthatcarbonminer- alization,fungalbiomass,andactivitiesofcellulolyticandhemicellulolyticenzymesde- creasedwithNavailability. Intheareaofcomparativeecosystemstudies,Sinsabaughetal.(62,63)followed massloss,NandPimmobilization,andactivityof11typesofextracellularenzymesfor birchsticks(Betulapapyfera)decomposingateightupland,riparian,andloticsitesover arst-orderwatershed.Masslossratesamongsitesvariedbyafactorof5andwere correlatedwithlignocellulaseactivities.Incontrast,relationshipsbetweenmasslossand activitiesofacidphosphataseand-1,4-N-acetylglucosaminidasevariedwidelyamong sites.TheserelationshipsalongwithanalysesoftheNandPcontentofthestickssuggested thatdifferencesinmasslossratesamongsitesweretiedtodifferencesinnutrientavail- ability. Inanotherexperiment,litterbagscontainingsenescentleavesofAgeratumconi- zoidesandMallotusphilippinensiswereplacedontheoorofayoungtropicalforestsite innortheastIndia(38).OtherlitterbagscontainingleavesofHolarrhenaantidysenterica andVitexglabratawereplacedatamaturetropicalforestsite.Athigher-elevationsubtrop- icalsites,litterbagscontainingPinuskesiyaandMyricaesculentaleaveswereplacedin ayoungforestandbagscontainingPinuskesiyaandAlnusnepalensisleaveswereplaced inamatureforest.Sampleswereanalyzedformassloss,bacterialandfungalnumbers, cellulosecontent,Ncontent,solublesugarcontent,andactivitiesofcellulase,amylase, andinvertase.Cellulaseandamylaseactivitieswerecorrelatedwithmicrobialnumbers. Invertaseactivitycorrelatedwithsolublesugarcontent.Enzymeactivitiesandmassloss rateswerehigheratthelowerelevationsitesbutwerenotrelatedtostandage.Inasimilar study,thedecompositionofPinuskesiyaandAlnusnepalensisatadisturbedroadside forestsitewascomparedwiththatatanundisturbedsite(30).Againcellulaseandamylase activitieswerecorrelatedwithmicrobialnumbers,whereasinvertaseactivitywaslinked tosolublesugars. DillyandMunch(18)studiedenzymeactivitiesandmicrobialrespirationforAlnus glutinosa(blackalder)leavesdecomposingatwetanddrysiteswithinafenforest.Mass lossratesweremorethantwiceasfastatthewetsite.Microbialbiomassandrespiration decreasedovertime(16to2.3àmolg 1 h 1 ),buttheefciencyofCutilizationincreased. Thesetrendswereparalleledbydecreasing-glucosidaseactivityandincreasingprotease activity. III.COMPARATIVEANALYSES Inthecontextofthesuccessionalloopmodel(Fig.1),therearethreedimensionsfor comparing ... wererepressedbyaddedN;formapleandoak,theseactivitiesincreased.Theresults suggestedthatwhiterotfungi,whichproduceligninasesinresponsetolowNavailability, weredisplacedbysupplementalN,slowingthedecompositionofrecalcitrantlitter. HenriksenandBreland(27)alsofocusedontheroleofNinthedecomposition process.Usingamicrocosmsystemofwheatstrawandsoil,theyfoundthatcarbonminer- alization,fungalbiomass,andactivitiesofcellulolyticandhemicellulolyticenzymesde- creasedwithNavailability. Intheareaofcomparativeecosystemstudies,Sinsabaughetal.(62,63)followed massloss,NandPimmobilization,andactivityof11typesofextracellularenzymesfor birchsticks(Betulapapyfera)decomposingateightupland,riparian,andloticsitesover arst-orderwatershed.Masslossratesamongsitesvariedbyafactorof5andwere correlatedwithlignocellulaseactivities.Incontrast,relationshipsbetweenmasslossand activitiesofacidphosphataseand-1,4-N-acetylglucosaminidasevariedwidelyamong sites.TheserelationshipsalongwithanalysesoftheNandPcontentofthestickssuggested thatdifferencesinmasslossratesamongsitesweretiedtodifferencesinnutrientavail- ability. Inanotherexperiment,litterbagscontainingsenescentleavesofAgeratumconi- zoidesandMallotusphilippinensiswereplacedontheoorofayoungtropicalforestsite innortheastIndia(38).OtherlitterbagscontainingleavesofHolarrhenaantidysenterica andVitexglabratawereplacedatamaturetropicalforestsite.Athigher-elevationsubtrop- icalsites,litterbagscontainingPinuskesiyaandMyricaesculentaleaveswereplacedin ayoungforestandbagscontainingPinuskesiyaandAlnusnepalensisleaveswereplaced inamatureforest.Sampleswereanalyzedformassloss,bacterialandfungalnumbers, cellulosecontent,Ncontent,solublesugarcontent,andactivitiesofcellulase,amylase, andinvertase.Cellulaseandamylaseactivitieswerecorrelatedwithmicrobialnumbers. Invertaseactivitycorrelatedwithsolublesugarcontent.Enzymeactivitiesandmassloss rateswerehigheratthelowerelevationsitesbutwerenotrelatedtostandage.Inasimilar study,thedecompositionofPinuskesiyaandAlnusnepalensisatadisturbedroadside forestsitewascomparedwiththatatanundisturbedsite(30).Againcellulaseandamylase activitieswerecorrelatedwithmicrobialnumbers,whereasinvertaseactivitywaslinked tosolublesugars. DillyandMunch(18)studiedenzymeactivitiesandmicrobialrespirationforAlnus glutinosa(blackalder)leavesdecomposingatwetanddrysiteswithinafenforest.Mass lossratesweremorethantwiceasfastatthewetsite.Microbialbiomassandrespiration decreasedovertime(16to2.3àmolg 1 h 1 ),buttheefciencyofCutilizationincreased. Thesetrendswereparalleledbydecreasing-glucosidaseactivityandincreasingprotease activity. III.COMPARATIVEANALYSES Inthecontextofthesuccessionalloopmodel(Fig.1),therearethreedimensionsfor comparing ... acid analysis), and activities of xylanase, laminarinase, phosphatase, urease, and chitinase. They found a correspondence between functional diversity and structural diversity, both peaking in spring. Others...

... enzymes in the upper part of the profile could be due to the presence of fungi (chitin in the cell walls) and arthropods (chitin in the exoskeleton) serving as substrates. Enzyme determination using ... the years; these include vanilin, indulin, ferrulic acid, and, most importantly, 14 C-labeled synthetic lignins. Various fungal enzymes are involved in lignin degradation, including lignin peroxidase, ... soils and horizons; for determining the effects of pollution and changes in climate and land use; and for using biomass data in decomposition models (13). The mycelium is often well hidden in soil...