Polarforschung58 (2/3): 189-/91,1988
2.9 Incorporation of Inorganic Carbon by Antarctic Cryptoendolithic Fungi
By Roben J. Palrner, Jr. ancl E. Imrc Frieelmann*
Summary: Fungiisolatcd from the cryptocndolithic community 01' thc Ross Desort arc offixmg inorganic carbon. Rcsults suggcst thutlichcn mycobionts and parasyrnbionts arc adaptcd(0different e-urer rcgimesin thccryprocndclith tc cnvironmcnt.
Zusammenfassung: Kryptocndolithischc die aus Sandstein der RossDescrt isoliert worden sind, können nicht Kohlenstoff fixieren. Es ist anzunehmen. diese Pilze als Mvkohiontcn oder als Parasvmbionten von Flechten hierin an verschiedene
hältnisscimGesteinsporenraum angcpußts i n d . ' -
1.INTRODUCTION
The main features ofthe cryptoenelolithic microbial community01'Antarctica 's Ross Desert have been elescribeel earlier (FRIEDMANN 1982), and the nanoclimate ofthe cryptoenelolithic microenvironment has becn studiccl to some extcnt (FRIEDMANN et al. 1987, NIENO\,Y et al. 1988a, b). PALMER (1987), YESTAL (1988), anel PALMER& FRIEDMANN (in press) founel significant uptake01'C02 by the community in the dark. In the present paper, we re port preliminary results indicating that fungal metabolism is responsible, ar least in part. for this heterotrophic carbon incorporation.
2. MATERIALS AND METHODS 2.1 Cultures
Fungal cultures are maintained in the Culture Collection 01' Microorganisms from Extreme Environments (CCMEE) at the Polar Desert Research Center. Floriela State University,
Strain F2 (A801-146) is a dark-pigmentcd fungus isolated from the Antarctic cryptoenelolithic community. In laboratory experiments, it eloes not form lichens anel is probably a parasymbionr (KORIEM& FRIEDMANN unpubl.).
Strain FIO is a hyaline fungus isolateel by Dr.V.Ahmadjian from the Antarctic cryptoenelolithic community. In laboratory experiments, it forms a liehen association and is therefore a mycobiont (AHMADJIAN&JACOBS 1987).
2.21l1corporaliol1 Oj'HC03-
Cultures were grown in malt-yeast extract medium in ISO-mi batches at 8-C.Pieces01'mycelia (5-30 mg elry weight) were transferreel aseptically to 5-ml aliquots01'10 mM NaP04 buffer (pH 6.8) in IO-ml screw-capped test tubes. After incubation at 8- C for 24 or 120 hours, 10!JI ofHI 4C03-solution was aeleleel to each tube, resulting in a final 14C concentration01'2.0--3.6 x 105
CPM (counts per minnte) mrI
Following one ho ur01'exposure to labelleel bicarbonate, the mycelia were washeel by centrifugation arid resuspension: twice with buffer. then twice with 0.1 N HCI to rcmove unincorporateel bicarbonate. Mycelia were collected on glass fiber filters, elrieel overnigh: at 60- C, and placeel in 5-ml aliquots01'liquiel scintillation fluid. Incorporation01'bicarbonate was assayeel in a Packarel 2045 scintillation spectrometer,
'" 01'.Robert1.Palmcr.11'. and Prof. Dr.E.Imre Priedmarm. Polar Desert Research Center. Dcpartment01'Biological Scicncc. Florida Stare Univcrsity.
Tallahassce.PI. 32306-2043. U.S.A. Currcnt addressforDr. Palrner: Institut für Alleemeine Mikrcbioloaic. Universitär Kiel. Biologiezentrum.
Ölshausenstraße40/60.D~2300Kiel,FcderalRepublic01'Gcnnany ~ ~
189
2.3 lncorporationO(C02
Pieces01'mycelia (7-30 mg dry weight) were collecteel on Nucleopore filters (24 mrn dia .. O.2,um pore size) anel washcd rhoroughly with elistilleel water. The filters were placeel on a paper towel to e1raw away excess water, transferred to an incubation chamber with controlleel matric water potential (PALMER et a!. 1987), and cquilibrated at lOOCke relative hurnidity at 8' C for 24 hours. After this incubation, 14C02/air, prepared anel assayed by the method01'BELLY&BROCK (1967), was injecteel into the system to the same final
"c
conccntration as in the bicarbonarc-incorporation experimcnts. After one hour in the presence01'labelleel C02. the Filters were storcd over concentrateel HCI for four hours to remove unicorporared bicarbonate anel elrieel ovcrnight at 60' C.Incorporation of raelioactivity was assayeel as in the bicarbonate experiments.
3. RESULTS
lncarporation01'HCO, - anclOfC02 by the fungal strains (Tab. I) took place unelerlow-nutricntconelitions becausc the mycelia were washeel ancl incubateel prior to introduction of the labelied carbon. Bicarbonate was taken up in significant amounts by strain F 10, but in only trace amountsbystrain F2. Strain F I0 appeared to incorporate bicarbonate sligluly rnore efficiently after 120 ho urs of incubation than after 24110urs of incubation, although the ditference was not statistically significant. Thc incorporation pauern for C02 (in air) was the opposite01'that for bicarbonate (in liquid medium): strain F2 incorporated significant. The incorporation pattern for C02 (in air) was thc opposite ofthat for bicarbonate (inliquielmeelium): strain F2 incorporateel significant amounts OfC02 .. whereas strain FIO incorparated only trace amounts.
CCME stmin
lncubanon pcriod
Cl-Mx mgdrywt1X111
IT'CO, "CC\
1'10 F2
24 hours 120110m;.;
24 hours 120 hours
327(:'ir}") 512(210) tracc tracc
u-acc ND.
120 (20) N.D.
Tab. 1: carhonbyAntarctic cyptocndolithicIungi.
or inIOWi; humiditv addition 01" '.leG,.lncorporation thcscs) for11=3. Trace=:lcss thnn twicc bnckground: =not~lctcrminccl.
4. DlSCUSSION
werc incubatcd Ior 24 or !20 hours in 10 n-MNaPO~ buffcr nonnalizcd10dry (6ft Cl wcight.stnndarddcviation (in parcn-
lncorporation of C02 in the e1ark is a notablc Feature01'carbon merabolism in the cryptoendolithic community.
C02 fixationbyfungi has been reported before; MOSES et a!. (1959) elemonstrated thatZvgorrhvnchus moelleri incorporates labeleel C02 by carboxylation01'pyruvate, ancl MIROCHA & DE VAY (1971) anel TRlBE&
MABADEJE (1972) showed that several fungi are able to grow using C02 or BCO,' as a carbon source. The fineling that fungi in the cryptoendolithic cornmunity arc capable01'fixing inorganic ca rbon is cornparible with these results, anel a metabolic pathway similar to that described by MOSES et al. (1959) may ex ist in the Antarctic cryptoendolithic community.
The different responses of strains F2 anel F10 under mall'ic (air) anel osmotic (liquid) conditions may be eeologically significant. FI 0 is a lichenmycobiont, anel lichens are known to prefer wet·dry cycIes (see LAWREY 19841'01'review). In aeldition, certain fungi are known to tolerate extremely low weller potentials (GRIFFIN&
LUARD 1979). Because wateI'availability in the cryptoendolithic environment is constantly changing, one coulel speClIlate that Iiehen fungi anel parasymbionts re1y on different water sources. Lichens may use liquiel water available after the short periods of snowme]t, whereas parasymbionts may be able to utilize water vapor anelmay therefore be bettel' aelapted to metabolism e1uring e1rought.
5. ACKNOWLEDGEMENT
This research was supporteel by NSF grant DPP·8314180 and NASA gnU1t NSG·7337 to ElF.
190
ncrc rcn cc s
Ahm a d i an. V.& Ja c0b s .J. B. Studios on thc dcvclopmcnt01'symhetic lichcns. Progress and problcms in lichcnology in thc - Bibl. Lichcnol. 25:
Belly. R. & B r0ck .T.(1967): Ecology of iron-oxidizing bactcria in pyritic matertals associatedwithcoal. .---J.BaU. 117:n(}--732.
Frie d man n E. I.(1982):Endolitlucmicroorgunisms in thc Antarcüc colddcsen.~·Scicncc 215: 1045-1053.
Frie d man n . E. I.. M c K u C.P.& Nie n0w .J.A. Tbc cryptocudolithic rnicrobial cnvironmcnt in thc Ross dcscrt01"Anmrctica:
Sntcllitc trunsmincd nanocfimatc datn. Polar Biol. 7: 273-287.
Gr iffin. D. M. & LIIa r d . E. 1. (1979): Watcr strcss and rnicrobial ccolouv. In:Shilo. M. (cd.) Strarcaics or Microhial Lifc in Extreme
Environments:49~",-"(-H-.Neo, York , ~. ~
La xv r cy.J. D. (1984): The Biology ofLichenixcd Fungi. NcwYork.
Mir0ch a .C.J.8: [)cV u v . J.E.(1971):Growth01'fungi on an inorgnnic medium. --- Can. J. Microbiol. 17: I~73--.. 1378.
1'0'10s c s . Y.. Hol m -I-Ians c n . O. 8:Ca 1 v in. M. (19,')9): Nonphotosynthctic fixanon of carbon dioxidcbyrhrcc microorgunisms. - 1.
Bactcriol. 77:70·~~7R.
Nie n0w ,1.A .. M c K a y . C. E 8:Fric d m n n11.E. nucrobial cnvironmcmInthc Ross Dcscrt01' Antarctica: Muthcmaticnl models01'thc thermal rcgimc.
Nic n0w .J. A.. lvi c K av. C. P.& Fric cl man1\. E. I. microbia! cnvironmcnt in thc Ross Desort of Antarctica: Light in thc photosynthetically activc region.-
Pa! m cr. R. J.. Jr. (1987): Water rclaüons und photosynthcsis of dcscn microorgnisms and lichcns. Ph. D. disscruuion. Florida Stare Univcrsity, Tallahassee. Horida.USA.
Pa 1m er. R. Jr.& Fricclrn n n n . E. I.(in Water rclations nnd photosynthexis of descrtmicroorgnnismsand lichcns. 11. Thc cryptocndolithic hnbitat01'hot und cold dcscrts. -- Ecol.
Pa 1 m cr. R. J..J r..Nie n0w .J. A.& Fricd m n11n . E. I. (1987): Control01'matncc-atcrpotentialhytcmpcraturc differential. J.
Microbiol. Mcthods 6: 323·---:n6.
Tri b c . H. T. & M a badeje. S. A. (1972): Growth01'molds onmcdiu prcparcdwithourorgnuic nutricnts. Trans. BI'. Mvcol. 50e. ,')g (I):
127-137.
V e stal .1.R. (1981'\): Carbon metabolism ofthc cryptocndohtluc ruicrobiota frorn thc Antnrctic Dosen. - App.Env.Microbiol. 54: 960-965.
191
