evidence for a biogenic, microorganismal origin of rock varnish from the gangdese belt of tibet

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  • Journal Identication = JMIC Article Identication = 1592 Date: March 10, 2011 Time: 5:1pm

    Micron 42 (2011) 401411

    Contents lists available at ScienceDirect

    Micron

    journa l homepage: www.e lsev ier .com

    Evidence for a biogenic, microorganismal origin oGangdese Belt of Tibet

    Xiaohong SchKlaus Pe lerb

    a National Reseb Institute for P , D-55c Institute of Ged Max Planck In

    a r t i c l

    Article history:Received 4 NoReceived in reAccepted 2 De

    Keywords:VarnishTibetBiogenic mineralizationMicroorganismsBiolmMars

    aterie X-rdevelron mae ba

    layer in those samples two forms of bacteria-like microorganisms exist; cocci as tightly packed bacterialaggregates [within varnish bodies], and bacillus-like microorganisms [within the varnish matrix, thatsurrounds the varnish bodies]. The bacillus-like forms are embedded in a network of laments that havediameters between 35 and 45nm. These bacilli with the surrounding laments are assumed to havebeen involved in biolm formation (synthesis of extracellular polymeric substances) prior to their live

    1. Introdu

    Rock va(1807) for tadverse climpotential binish, a termof thin coatmicrometerSharp, 1958et al., 2003clay mineraganese [Mnand Post, 2and electronanalyses th

    Corresponberg UniversitTel.: +49 6131 Correspon

    E-mail add(W.E.G. Mller

    0968-4328/$ doi:10.1016/j.burial. We concluded that the formation of the varnish layers was for the most part biogenically drivenby microorganisms.

    2010 Elsevier Ltd. All rights reserved.

    ction

    rnish has interested geo-biologists since Humboldtwo reasons, rst to understand mineral formation inates and second to obtain further insights into the

    ogenic basis for mineral formation on Mars. Rock var-established by Dorn and Oberlander (1980), consists

    ings on rock surfaces, measuring usually between a fewand 3mm (reviewed in Laudermilk, 1931; Engel and; Broecker and Liu, 2001; Hodge et al., 2005; Perrya, 2004). Varnish is a brown-black layered veneer ofl on rocks that is rich in oxides and hydroxides of man-] and iron [Fe] (Potter and Rossman, 1977; McKeown001; Garvie et al., 2008). In spite of intensive light--microscopic investigations coupledwith geochemicale mechanism of nucleation and growth of rock var-

    ding author at: Institute for Physiological Chemistry, Johannes Guten-y, Medical School, Duesbergweg 6, D-55099 Mainz, Germany.39 25910; fax: +49 6131 39 25243.ding author. Tel.: +49 6131 39 25910; fax: +49 6131 39 25243.resses: wxh0408@hotmail.com (X. Wang), wmueller@uni-mainz.de).

    nish remains uncertain (Israel et al., 1997; Dorn, 1998; Perry et al.,2003a, 2004).

    The main components of rock varnish, Fe and Mn are widelyused in the organic world as cofactors for electron transfer pro-cesses (see Ehrlich, 2002; Tebo et al., 2005; Edwards et al., 2005).Two mechanisms of oxidation have been distinguished: rst theassimilatory metabolism of Mn and Fe, which involves cellularuptake and subsequent function in the cell metabolism, and sec-ond, the dissimilatory metabolism in which Mn and Fe serveeither as energy source or as terminal electron acceptor, depend-ing on the oxidation state (Ehrlich, 2002). While in the assimilatorymetabolism, small quantities of Mn and Fe are involved per cell,in the dissimilatory metabolism, much larger quantities of Mn andFe are involved and consumed per cell. Moreover, in the assimila-tory metabolism, Mn and Fe need to be taken into the cell whilein the dissimilatory metabolism (energy metabolism) Mn and Feappear to be acted upon on or in the cell envelope. During thosemetabolic processes the metal can be deposited in the terres-trial and aquatic environment on organic templates (see Glasby,2006; Wang and Mller, 2009), as has been determined for man-ganese/polymetallic nodules (Wang et al., 2009c) or crusts (Wanget al., 2009a, 2009b). These forms of organic template-driven min-eralization have been termed biomineralization by LowenstamandWeiner (Lowenstam and Weiner, 1989; see also Weiner and Dove,

    see front matter 2010 Elsevier Ltd. All rights reserved.micron.2010.12.001Wanga,b,, Lingsen Zengc, Matthias Wiensb, Uteter Jochumd, Heinz C. Schrderb, Werner E.G. Mlarch Center for Geoanalysis, 26 Baiwanzhuang Dajie, CHN-100037 Beijing, Chinahysiological Chemistry, Johannes Gutenberg University, Medical School, Duesbergweg 6ology, Chinese Academy of Geological Sciences, CHN-100037 Beijing, Chinastitute for Chemistry, J.J. Becherweg 27, D-55128 Mainz, Germany

    e i n f o

    vember 2010vised form 2 December 2010cember 2010

    a b s t r a c t

    In the present study we examined mperformed by use of energy dispersivwhether the varnish layers that hadvarnish bodies and silica glaze. Electis covered both by lamentous hyph/ locate /micron

    f rock varnish from the

    lomacherb,,

    099 Mainz, Germany

    al from the Ashikule Basin of Tibet. Chemical analyses wereay spectroscopy and electron probe microanalysis to clarifyoped on the surface of the rhyolite are indeed composed oficroscopic analyses revealed that the surface of the varnishcterial and cocci-shaped forms. Within the varnish mineral

  • Journal Identication = JMIC Article Identication = 1592 Date: March 10, 2011 Time: 5:1pm

    402 X. Wang et al. / Micron 42 (2011) 401411

    2003). Biomineralization refers to those mineralization processesthat occur in close association with organic molecules or matri-ces or is even (micro)biologically mediated. While mineralizationfollows exclusively chemical and physical principles and results inthe accumuparticipatiotion are indinduced miorganic scaof biologicametallic no2009b) whare themajoton of largeet al., 2008;

    Rock dessemi-arid rDeserts of tPotter and(Krumbeinof WesterntheGangdethe formatibeen proposition of thet al., 1985)the ferromato capillarythermore, tand rain, asand Sharp,Rossman, 1(Perry et altion of micanalysis ofstrong evidhas been pthe presencmanganesevarnish asinitiation oflarge variet2006). In adhas been derole has alsoGeorge et aproposed th(Allen et al.et al., 2002)tion by extrin older var(Perry andsea manganBoussingaurial stromathas been de

    The growabout 40nated layersituations,mtal moisturIn turn roctal processemore, varnitures andvacycle of sul

    rock varnish has attracted archeologists to date petroglyphs thatwere etched into varnish by ancient cultures (Dragovich, 2000;Watchman, 2000).

    In the present study we investigated rock varnish from thele Basin of Tibet. This region has been characterized to showity tally tn ofessue Ml precrrestcentlrnislazen varthreerialNo dregithe vrstlybod

    s tha. Scaia aresubstown000)oilscmaes, list ong elion c

    teria

    ck v

    Linzngdey (70Centet al.he Ysystetheese Bndiay meby rostudyatedmedthe re Oliat 2

    re w-K rRIMPnisht to ef recithilation of inorganic materials from solution without anyn of organic molecules, the processes of biomineraliza-uced on the surfaces of organic templates [biologicallyneralization], or are almost entirely controlled by anffold [biologically controlled mineralization]. Exampleslly induced mineralization are the formations of poly-dules (Wang et al., 2009c) or crusts (Wang et al., 2009a,ereas biologically controlled mineralization processesrprinciple in the formationof thehard, inorganic skele--sized animals (see Weiner and Dove, 2003; SchrderMller et al., 2009).ert varnish coatings are formed in numerous arid and

    egions of the world, including the Sonoran and Mojavehe United States and Mexico (Engel and Sharp, 1958;Rossman, 1977), the Negev Desert in the Middle Eastand Jens, 1981), the Gibson and Great Victoria DesertsAustralia (Beard, 1970), and the Gobi Desert as well asse Belt region in Tibet of China (Krinsley et al., 2009). Foron of varnish abiogenic as well as biogenic origins havesed. The assumption of an inorganic, abiogenic depo-e varnish coatings (Potter and Rossman, 1977; Blumeis based on experiments suggesting that deposition ofnganese oxides within the clay matrix of varnish is duemovement of varnishing solutions from the rocks. Fur-he minerals have been proposed to originate from dustwell as from the surrounding soils (Allen, 1978; Engel

    1958; Scheffer et al., 1963; Krumbein, 1969; Potter and979). In a series of thorough studies the group of Perry., 2003b) provided strong evidence for the participa-roorganisms in growth of these rock coatings, e.g. bythe amino acid composition of varnish. Furthermore,ence for the existence of bacteria within the varnishrovided by Krumbein and Jens (1981) who observede of microorganisms with a potential for iron and/orprecipitation in these coatings on the surface of the

    well as within these minerals. Subsequently, biogenicvarnish formation was frequently suggested when of ay of bacteria was isolation (reviewed by Kuhlman et al.,dition, the isolation of fungi from the surfaces of varnishscribed (Staley et al., 1982; Staley et al., 1983) whosebeen implicated in varnish mineral formation (Taylor-

    l., 1983; Gorbushina et al., 1993). Finally, it had beenat varnish or varnish-like materials may exist on Mars, 2001; Guinness et al., 1997; Israel et al., 1997; Probst, and hence varnish might be a niche for the coloniza-aterrestrial life forms, such as bacteria. Often, especiallynishes a layered botryoidal structure has been observedAdams, 1978) which displayed similarities to the deepese nodules, a view that had already been discussed bylt (1882).Also similarityof thevarnishwithcyanobacte-olites (Monty, 1973; Krumbein and Lange-Giele, 1979)scribed.th rate of the varnish is slow and amounts to 1 to

    m per 1000 years (Liu and Broecker, 2000). The lami-ing of the varnish is surely an indicator for past climaticirroring especially the past alterations in environmen-

    e (Liu and Broecker, 2000; Broecker and Liu, 2001).k varnish harbors historical re