Biomineralization in natural environments : the effect of microorganisms inhabiting hot spring water and biomats on mineral formation
著者 Belkova Natalia journal or
publication title
博士学位論文要旨 論文内容の要旨および論文審査 結果の要旨/金沢大学大学院自然科学研究科
volume 平成18年1月
page range 100‑104 year 2006‑01‑01
URL http://hdl.handle.net/2297/16713
氏名 学位の種類 学位記番号 学位授与の日付 学位授与の要件 学位授与の題目
BELKOVANATALIA
博士(学術)
博甲第691号 平成16年9月30日
課程博士(学位規則第4条第1項)
Biomineralizationinnaturalenvironments:theeffectofmicroorganisms
inhabitinghotspringwaterandbiomatsonmineralformation
(自然環境下における生体鉱物化作用:温泉水およびバイオマットに生息する 微生物が鉱物形成に及ぼす影響について)
田崎和江(自然科学研究科・教授)
奥野正幸(自然科学研究科・教授),加藤道雄(自然科学研究科・教授),
古本宗充(自然科学研究科・教授),中村省吾(富山大学・教授)
論文審査委員(主査)
論文審査委員(副査)
学位論文要旨
Abstract:BacterialmineralizationorbiomineralizationisaconⅡnonand
widespreadphenomenonoccurringinvarlousgeotllennalsystelns・Ani〃s〃
visualizationofthefbssilizedmicroorganismsintllegreenbiomatsanddepositsof tlleKotelnikovskyhotsprings(LakeBaikal,Russia),allowedconcludingtllat silicificationandcalcificationoftllemicroorgamsmsextensivelyappearedmthe biolnatsanddepositsunderpH8.Ohydrothemalconditions・Thetllermalwaterof theVilyuchinskiesprings,Kamchatkapeninsula,Russia,showedtlleoxidativeeffect oftheoxidation-reductionpotential,hadatemperatureof56oC,aneutralpHand lligdlcontentsofironandsilicicacids,FerricironpredominatedovertlleferrousfbrTn ataratioof52:7mthebrownbiomats・Theacceleratedprocessesofironoxidation,
silicification,anddepositionofFe-Simineralsthatoccurinthebrownbiolnatscan beattributedtotlleimpactofrod-shapedbacteriainhabitingthehotspringwaterand bionlats、ApositivecorrelationbetweentlleactivityofFe-bacteriaintllewater,tlleir presencemthebiomats,andthechemicalcontentofwateranddepositswasfbund fbrOksmskie,Nalychevskie,andDaclmyehotsprings(Kamchatkapeninsula,
Russia).Inchemolithotropllicenvironlnents,tllenlicrobialabundanceandtlletypes ofbacterialactivitiesreflectthebiologicalcomponentsoftllebiogeoCllemical
-100-
processesoccurnngintheecosystem・
Bacterialnlineralizationorbionlineralizationisaconunonandwidespread phenolnenonoccurringinvarlousgeotllennalsystelns・TheimportantlDleof nncroorganlsmsmtllefbnnationofmodernhydrothennaldepositswasdenoted recentlyBacteriaareverysmall(~1.5卜Im3),buthavetllelargestsurfacetovolume ratioofanylifefbnnTherefbre,tlleyprovidealargecontactareatllatcaninteract withlnetalsintllesunDundmgenvironments・Microbialactivityisresponsiblefbrtlle transfbnnationofatleastonetllirdoftlleelelnentsintlleperiodictable・Themain ol。jectiveofthepresentstudywastoinvestigatehotspringwater,biomatsand depositsmordertoobservenllcroorganlsnlsthatcouldbeactivelyinvolvedin biogemcn血eralfbrmationandwereassociatedwitlllnmcralparticles・
Samplesofwater,greenbiomatsandmodernhydrotllennaldepositswere collectedfiomtwosamplingareasnamelyLakeBaikal,SiberiaandKamchatka peninsula,Russia、Physicochemicalvariablesofthehotspringwater[pH,oxidation‐
reCluctionpotential(E11),electricalconductivity(EC),dissolvedoxygen(DO),water temperature(WT)]weremeasuredmthefieldWater,biomats,anddepositswere analyzedchemicallywitllenergydispersiveX-rayspectrometer・Mineralogical colnpositionofgreenbiomatsanddepositswasidentifiedwitllX-raydiffieactolneter・
Microscopicobservationofbacteriainhabitinghotspringwaterandbiolnatswas donewitllopticalmicroscopy、Fossilizedmicroorganisnlsingreenbiomatsand depositsaswellasdolninantbacterialspeciesinhotspringwaterswerestudiedwith scannlngandtranSInissionelectronlniclDscopyequippedwitllenergydispersiveX‐
rayspectrometer・Additionally,tllermoplliliclnicroorgamsmsisolated丘omwater andbiomatsofKotelmkovsky,Khakusy,andZmeinayahotsprings(LakeBaikal,
Russia)andconsortiulnofculturableiron-oxidizingbacteriafiDInVilyuchinskiehot
Springs(Kamchatkapemnsula,Russia)weresmdiedinlaboratoryexperilnents.
Activityofmicroorgamsnlswasestinlatedノ川j〃innaturalsamplesofhotspring
watersandfbrculturabletllennopllilicbacteria・
A1kalineandneutralpHfbrBaikalandtlleKamchatkahotSprings,respectively,
wererevealedduringmeasurementsofphysicochemicalvariables・Lowvaluesof dissolvedoxygenandhigilwatertelnperatureweremainlydetennmed・General featureofchelnicalcompositionofhotspringwatersishigllcontentofSi・Calcium andsiliconweredetectedinllighcontentindepositsaswellasingreenbionlatsfiom theKotelnikovskyhotsprings,while,ironandsiliconwerefbundnlainlyintlle Vilyuchinskiehotsprings、Additionally,biolnatswereenrichedinbio-elementssuch aspotassium,magnesiuln,iron,phosphorus,andsulfhr・
Ani川j〃visualizationoftllefbssilizednlicroorganislnsintllegreenbiomatsand depositsoftheKotelnikovskyhotspringslocatedontllenorthwestcoasto缶Lake Baikal,Russia,allowedconcludingtllatsilicificationandcalcificationofthe nncroorgamsmsextensivelyappearedinthebiolnatsanddCpositsunderpH8.O 11ydrothermalconditions・Thebiologicallymducedprecipitationcouldbeproposed fbrcalcitefbrmationinthehotSpringwaters,whereas,biologicallycontrolled lnineralizationofSi-Camaterialscouldbedenotedfbrgreenbiomatsanddeposits・
nleessentialroleofsilicateionshasbeenproposedfbrthefbnnationofamorphous
structureswhicharerichincalcium
TY1eculturecollectionofculturablethennophilicbacteriaisolatedfiomwaterand
biolnatsofKotelnikovsky,Khakusy,andZ1neinayahotspringsincludestotally91 strainswllichweregrownat53oCMostofisolatedstrainsweregram-positivespore‐
fbrnmngrodsandbelongedtogenusBacjノルs、Itwasdenotethattllemghestfiaction ofstrainsshowedhigherdegreeofvariableenzymaticactivitiesratherattemperature
of50oCthantllatat20oC.
ThetllermalwaterofUleVilyuchinskiesprings,nalnelyV3site,Kamchatka
-102-
peninsula,Russia,showedtheoxidativeeffbctoftheoxidation-reductionpotential,
hadneutralpH,watertemperatureof56oCandallighironconcentration・Ferriciron predonmnatedoverthefelrousfbnnataratioof5Z:7intllebrownbiolnats、Respiring iron-oxidizmgbacteriawerepresentintllewaterfromtlleV3springandiron‐
bacteriawereisolatedfiomtllebiomats・hculturediron-oxidizmgbacteria,
arnolphouslnineralparticleswereobservedaroundtllebacterialce11s,sUggestmgtllat Fe(IDoxidationiscatalyzedormediatedbytllesenlicroorgamsnls、Moreover,tlle
watersoftlleVilyuchinskieSpringsareriChin silicicacidandthereisarapidrateof silicificationduringwaterdischargeand coolmgTheacceleratedplocessesofiron oxidation,silicification,amdepositionofFe-
Simineralsthatoccurmtllebrownbiomats
oftlleVilyuchinskayahydrotllerlnalsystem canbeattributedtotheilnpactofrod-shaped bacteriainhabitingtllehotspringwatersand biomats(Fig.1).
Fig.1.Scanmngelectronmicrographofrod- shapedbacteriainhabitingbiomatsofthe Vilyuchmskiehotsprmgs,KaInchatka peninsula,Russia,thoseareresponsiblefbr
Fe-mineralfbImation.
Additionalandvelyilnportantdatawereobtamedfronlbacterialenumerations、A positivecolrelationwasfbundbetweenthepercentofCFDA+cellsandtllepHoftlle waters・Respiringiron-oxidizingbacteriawereobservedinthewateroftlleOksmskie,
Nalychevskie,andDachnyespnngs,andgrowthofFe-oxidizingbacteriawas obtainedonFe-agarplateswitllinoculationsfiolntlleNalychevskieandDachnyehot springbiomats・Tllus,tllereisapositivecorrelationbetweentlleactivityofFe‐
bacteriamthehotspringwater,theirpresenceinthehotspringbiomats,andthe
chemicalcontentofhotspringwateranddeposits、misilnportanttopointouttllattlle
lnetabolicactivityoflnicroorgamslns,suchasiron-oxidizingbacteria,canmduce
mineralprecipitationasasecondaryby-product;aprocessreferredtoasbiologically
l
mducedmineralization.
学位論文審査結果の要旨
平成16年7月15曰に第1回学位論文審査委員会を開催し,7月28曰に口頭発表を行い,同曰 最終の審査委員会を開催した.協議の結果以下のとおり判定した.本学位論文は,ロシア・バイカル 湖畔のKotelnikovsky温泉及びロシア・カムチヤツカ半島の4つの温泉(Vilyuchinskie,Oksinskie,
Nalychevskie,Dachnye)についてそれぞれに生成する多様な温泉バイオマットを地球科学的また微生物学 的な視点から研究し,生体鉱物化作用の特徴を議論したものである。バイカル湖のKotelnikovsky温泉の緑 色パイオマット及び堆積物中の微生物の観察から,pH80以下の熱水条件下では微生物により蛍石と方解石 が形成される.カムチャツカ半島のVilyuchinskie温泉は鉄と珪酸に富む中'性の温泉である。ここでは,褐
色パイオマツト中の第一鉄:第二鉄の比が52:7でありフェリハイドライトが形成するが,これはバイオマッ ト中の桿菌の酸化作用によると考えられる.カムチャツカ半島のOksinskie,Nalychevskie,Dachnye温泉 では鉄バクテリアの存在およびその活性,温泉水と堆積物中の鉄の含有量の間には正の相関関係があること が明らかになった.これらの温泉環境下では,微生物の存在割合と微生物学的活性度が生体鉱物の形成に関 与する.参考論文は二つが受理ざれ印刷中である。以上5名の審査員はいずれも学位に相当する質の高い
論文であると評価し,博士(学術)に値するものと認定した.づ、