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...of images of stacks and extraction of XANES spectra were done using the aXis2000ssoftware (Ver 2.1n). Spectral peak positions, intensities and widths were determined using the Athenassoftware package =-=[50]-=-. The XANES spectra shown in the present contribution correspond toshomogeneous organic-rich areas of several hundreds of nanometers. Although radiation damage persunit of analytical information has b...

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... biologically mediated calcification of bacteria, which is involved in thesformation of stromatolites or microbialites [30–32], has been described as a key process contributingsto their fossilization =-=[27,29,30,33]-=-. The propensity of biogenic organo-mineral assemblages tosovercome degradation during diagenesis might be dependent upon a number of parameters, includingsthe paleoenvironmental and diagenetic condit...

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...ilar perspective, the sizes and morphologies of the discoid, lobed and rhizoid structures formedsby the assemblage of these sticks are consistent with bacterial colonies at different stages ofsgrowth =-=[56,57]-=-. Observations of cross-sections reveal that these epibiotic structures have a meansthickness of about 15 μm with a thicker central part (Figure 4).sMinerals 2015, 5 493sFigure 2. Morphologies of the ...

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... biologically mediated calcification of bacteria, which is involved in thesformation of stromatolites or microbialites [30–32], has been described as a key process contributingsto their fossilization =-=[27,29,30,33]-=-. The propensity of biogenic organo-mineral assemblages tosovercome degradation during diagenesis might be dependent upon a number of parameters, includingsthe paleoenvironmental and diagenetic condit...

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...ture (XANES) measurements of the present study were done usingsthe Scanning transmission X-ray microscope (STXM) located on beamline 5.3.2.2 (STXM Polymersbeamline) at the Advanced Light Source (ALS) =-=[49]-=-. Beamline 5.3.2.2. (ALS) uses soft X-rayss(250–800 eV) generated via a bending magnet while the electron current in the storage ring is heldsMinerals 2015, 5 492sconstant in top-off mode at 500 mA at...

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...he presence of ~1 μm wide stick-like carbonate structures exhibiting ansabsorption peak at 288.6 eV in their C-XANES spectra. This peak could be attributed to the presencesMinerals 2015, 5 499sof EPS =-=[85]-=-. These minerals may thus result from extracellular precipitation of amorphous carbonatessthat may preferentially occur onto EPS molecules. The vertical orientation of the carbonate sticks maysbe rela...

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... been performed at low Ga-ion currents using the FEI STRATAsDB 235 FIB system operating at the IEMN (Lille, France) to prepare electron and soft X-raystransparent ~15 μm × 5 μm × 80 nm cross-sections =-=[40]-=-. This extraction procedure maintains texturalsintegrity, even in the case of loosely consolidated materials [41,42], and prevents shrinkage andsdeformation of microscale to nanoscale pores, even in t...

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...icrometric association of calcite with organic molecules dominated bysproteic moieties exhibited by the contemporary bacterial colonies suggests a formation resulting fromsbiomineralization processes =-=[60,70]-=-. Two main pathways of bacteria-induced/controlled carbonatesprecipitation have been reported in modern environments and laboratory cultures [64,71–74].s(1) The formation of miscellaneous crystalline ...

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... may also be producedsthrough abiotic processes [18,19]. Adding to controversies, bio-alteration and burial-induced processessinevitably alter the original biochemical signatures of organic molecules =-=[20,21]-=-. As a result, thesgeneral paleobiological perception has long been that burial and diagenetic processes are detrimentalsto the preservation of biosignatures. Yet, metamorphic rocks may retain, to som...

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...90.3 eV attributed to 1s → π* electronic transitions ofscarbon in carbonate groups (CO3) (Figure 6) [58] and a second absorption peak at 288.6 eV, generallysattributed to carboxylic functional groups =-=[59]-=-. Such C-XANES spectra have been previouslysattributed to carbonates closely associated with organics [60–62]. These stick-like low Mg-carbonatessclosely associated with organics are consistent with c...

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... for multiple strains of cyanobacteria [73,83], may lead to the accumulation ofscalcium carbonates within bacterial cells. Whereas gas vesicles function as flotation devices insplanktonic prokaryotes =-=[84]-=-, the precipitation of intracellular carbonates has been proposed tospotentially serve as ballasts [73], thus facilitating benthic (or epibiotic) modes of life. Additionally,ssuch carbonate precipitat...

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...iotic structures have been observed on these fossilized shrimps compared tostheir modern counterparts, they cover about 5% of their surface (Figure 1). Fossilization of thesesshrimps occurred rapidly =-=[39]-=-, through a quite common mineralogical diagenetic sequence (apatite,scalcite, gypsum, pyrite, chalcopyrite and galena), indicating quite low diagenetic pressure andstemperature conditions.sFigure 1. I...

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...ilar perspective, the sizes and morphologies of the discoid, lobed and rhizoid structures formedsby the assemblage of these sticks are consistent with bacterial colonies at different stages ofsgrowth =-=[56,57]-=-. Observations of cross-sections reveal that these epibiotic structures have a meansthickness of about 15 μm with a thicker central part (Figure 4).sMinerals 2015, 5 493sFigure 2. Morphologies of the ...

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...noxygenic photosynthesis [63,79–82].s(2) Alternatively, biomineralization may occur intracellularly. Intracellular carbonate precipitation,sas recently evidenced for multiple strains of cyanobacteria =-=[73,83]-=-, may lead to the accumulation ofscalcium carbonates within bacterial cells. Whereas gas vesicles function as flotation devices insplanktonic prokaryotes [84], the precipitation of intracellular carbo...

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...ation and diagenetic processes. Last, trapping of organics within minerals upon diagenesis andseven metamorphism has been shown to allow, to some extent, the preservation of geochemicalsbiosignatures =-=[14,24,25,29,88]-=-.sHere, the morphologies of the fossilized calcifying bacterial colonies appear very similar to the onessof the contemporary colonies, even down to the submicrometer scale. Such fine-scale morphologic...

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...ation and diagenetic processes. Last, trapping of organics within minerals upon diagenesis andseven metamorphism has been shown to allow, to some extent, the preservation of geochemicalsbiosignatures =-=[14,24,25,29,88]-=-.sHere, the morphologies of the fossilized calcifying bacterial colonies appear very similar to the onessof the contemporary colonies, even down to the submicrometer scale. Such fine-scale morphologic...

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...pollenin or chitin [14–17], identification of remains of micro-organismsswithin fossilized structures remains complicated as microbial-like morphologies may also be producedsthrough abiotic processes =-=[18,19]-=-. Adding to controversies, bio-alteration and burial-induced processessinevitably alter the original biochemical signatures of organic molecules [20,21]. As a result, thesgeneral paleobiological perce...

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...d cuticles.sAlthough these carbonates might have first been small amorphous spheres within the bacteria cells,sthey may have merged and evolved towards crystalline calcite after the death of bacteria =-=[78]-=-.s4.2. Fossilization of Calcifying Bacterial ColoniessPreservation of chemical and/or morphological bacterial signatures in fossils is promoted by severalsfactors in addition to limited heterotrophic ...

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... redeposition of the sputtered material on the sample surface [41,42,45–47].sIn addition, milling at low Ga-ion currents prevents significant changes in the speciation of complexscarbon-based polymer =-=[15,48]-=-.s2.5. Transmission Electron Microscopy (TEM)sTransmission electron microscopy (TEM) analyses of FIB section were performed with a 200 kVsJEOL 2100 field emission gun (FEG) microscope (JEOL Ltd, Tokyo...

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...cterial ultrastructures has also been shown to influence the extent of biosignaturespreservation. For instance, periplasm encrustation has been described as favoring bacterial morphologyspreservation =-=[26,61,86]-=-. Specific crystallographic orientation (perpendicular to cell walls) ofscrystalline phases precipitated within bacterial periplasm [61,86,87], at the cell surface or in associationswith cyanobacteria...

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...e) to prepare electron and soft X-raystransparent ~15 μm × 5 μm × 80 nm cross-sections [40]. This extraction procedure maintains texturalsintegrity, even in the case of loosely consolidated materials =-=[41,42]-=-, and prevents shrinkage andsdeformation of microscale to nanoscale pores, even in the case of highly sensitive materials [43,44].sMilling at low Ga-ion currents has allowed preventing common artifact...

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... redeposition of the sputtered material on the sample surface [41,42,45–47].sIn addition, milling at low Ga-ion currents prevents significant changes in the speciation of complexscarbon-based polymer =-=[15,48]-=-.s2.5. Transmission Electron Microscopy (TEM)sTransmission electron microscopy (TEM) analyses of FIB section were performed with a 200 kVsJEOL 2100 field emission gun (FEG) microscope (JEOL Ltd, Tokyo...

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...f the carbonate sticks maysbe related to that of the calcifying bacteria anchored at the surface of the decapod cuticle, as it hassalready been observed for filamentous cyanobacteria in stromatolites =-=[74]-=-. In these formations,sheterotrophic degradation of cyanobacterial EPS is generally invoked to explain the progressivesreplacement of amorphous carbonates by calcite, leading to a porous microstructur...

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...2+sand dissolved inorganic carbon concentrations) that can be controlled by biological activity fromsdifferent metabolisms such as sulfate-reduction, oxygenic or anoxygenic photosynthesis [63,79–82].s=-=(2)-=- Alternatively, biomineralization may occur intracellularly. Intracellular carbonate precipitation,sas recently evidenced for multiple strains of cyanobacteria [73,83], may lead to the accumulation of...

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...ly because of their poor resistance tosdiagenetic degradation. For instance, only some rare fossilized examples of epibiosis have beensreported within Precambrian rocks such as the Gunflint Formation =-=[13]-=-. Nevertheless, documentingssuch interspecific associations over geological timescales may provide new insights into processes andsmechanisms of evolution as well as into paleoenvironments and paleoco...

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...pollenin or chitin [14–17], identification of remains of micro-organismsswithin fossilized structures remains complicated as microbial-like morphologies may also be producedsthrough abiotic processes =-=[18,19]-=-. Adding to controversies, bio-alteration and burial-induced processessinevitably alter the original biochemical signatures of organic molecules [20,21]. As a result, thesgeneral paleobiological perce...

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...ral structures observed on thescarapace of contemporary decapods (shrimps) from La Paz Bay (Mexico) as well as on fossilizedscounterparts from the Callovian Lagerstätte of La Voulte-sur-Rhône, France =-=[34]-=-. Of note, a number ofsstudies have reported the presence of epibiotic micro-organisms, such as diatoms, cliliates andsbacteria, on extant decapods [10,35–38]. Here, the use of advanced analytical tec...

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...cterial ultrastructures has also been shown to influence the extent of biosignaturespreservation. For instance, periplasm encrustation has been described as favoring bacterial morphologyspreservation =-=[26,61,86]-=-. Specific crystallographic orientation (perpendicular to cell walls) ofscrystalline phases precipitated within bacterial periplasm [61,86,87], at the cell surface or in associationswith cyanobacteria...

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... biologically mediated calcification of bacteria, which is involved in thesformation of stromatolites or microbialites [30–32], has been described as a key process contributingsto their fossilization =-=[27,29,30,33]-=-. The propensity of biogenic organo-mineral assemblages tosovercome degradation during diagenesis might be dependent upon a number of parameters, includingsthe paleoenvironmental and diagenetic condit...

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...cesses (i.e., biodegradation of organic matter) [33]. Forsinstance, carbonate and phosphate biomineralization has been shown to efficiently preserve molecularssignatures of biogenic organic molecules =-=[28,29]-=-. In addition, the location of mineral precipitation withsrespect to the bacterial ultrastructures has also been shown to influence the extent of biosignaturespreservation. For instance, periplasm enc...

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... biologically mediated calcification of bacteria, which is involved in thesformation of stromatolites or microbialites [30–32], has been described as a key process contributingsto their fossilization =-=[27,29,30,33]-=-. The propensity of biogenic organo-mineral assemblages tosovercome degradation during diagenesis might be dependent upon a number of parameters, includingsthe paleoenvironmental and diagenetic condit...

Citation Context

...e) to prepare electron and soft X-raystransparent ~15 μm × 5 μm × 80 nm cross-sections [40]. This extraction procedure maintains texturalsintegrity, even in the case of loosely consolidated materials =-=[41,42]-=-, and prevents shrinkage andsdeformation of microscale to nanoscale pores, even in the case of highly sensitive materials [43,44].sMilling at low Ga-ion currents has allowed preventing common artifact...

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...texturalsintegrity, even in the case of loosely consolidated materials [41,42], and prevents shrinkage andsdeformation of microscale to nanoscale pores, even in the case of highly sensitive materials =-=[43,44]-=-.sMilling at low Ga-ion currents has allowed preventing common artifacts like local gallium implantation,smixing of components, creation of vacancies or interstitials, creation of amorphous layers, lo...

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...han in TEM-based electron energy loss spectroscopy (EELS) [51–54], thesC-XANES data shown here have been collected following the procedures for X-ray microscopysstudies of radiation sensitive samples =-=[55]-=-.s3. Resultss3.1. Contemporary Epibiotic Organo-Mineral Structuress3.1.1. MorphologysThe investigated contemporary epibiotic organo-mineral structures appear as rigid, flat andstransparent structures ...

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...cterial ultrastructures has also been shown to influence the extent of biosignaturespreservation. For instance, periplasm encrustation has been described as favoring bacterial morphologyspreservation =-=[26,61,86]-=-. Specific crystallographic orientation (perpendicular to cell walls) ofscrystalline phases precipitated within bacterial periplasm [61,86,87], at the cell surface or in associationswith cyanobacteria...

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...icrometric association of calcite with organic molecules dominated bysproteic moieties exhibited by the contemporary bacterial colonies suggests a formation resulting fromsbiomineralization processes =-=[60,70]-=-. Two main pathways of bacteria-induced/controlled carbonatesprecipitation have been reported in modern environments and laboratory cultures [64,71–74].s(1) The formation of miscellaneous crystalline ...

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... Minerals 2015, 5 489s1. IntroductionsEpibiosis, the association between two species in which one (the epibiont) spends a portion of itsslife attached to the surface of the second one (the basibiont) =-=[1]-=-, has likely involved a broad diversitysof taxa over geological time as evidenced by a number of studies having reported fossilized symbioticsorganisms [2–12]. Yet, identifying such ancient interspeci...

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...grity. Epibiotic organo-mineral structures have beensdetected on the whole carapace (pleon, carapace and telson) of most of the 20 sampled specimens,scovering up to 10% of the whole animal (Figure 1) =-=[11]-=-.sThe investigated fossilized counterparts have been observed on the carapace of two fossil decapodss(Archeosolenocera straeleni Carriol and Riou, 1991, UMPC-150 and Aeger brevirostris Van Straelen,s1...

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... may also be producedsthrough abiotic processes [18,19]. Adding to controversies, bio-alteration and burial-induced processessinevitably alter the original biochemical signatures of organic molecules =-=[20,21]-=-. As a result, thesgeneral paleobiological perception has long been that burial and diagenetic processes are detrimentalsto the preservation of biosignatures. Yet, metamorphic rocks may retain, to som...

Citation Context

...ation and diagenetic processes. Last, trapping of organics within minerals upon diagenesis andseven metamorphism has been shown to allow, to some extent, the preservation of geochemicalsbiosignatures =-=[14,24,25,29,88]-=-.sHere, the morphologies of the fossilized calcifying bacterial colonies appear very similar to the onessof the contemporary colonies, even down to the submicrometer scale. Such fine-scale morphologic...

Citation Context

...ation and diagenetic processes. Last, trapping of organics within minerals upon diagenesis andseven metamorphism has been shown to allow, to some extent, the preservation of geochemicalsbiosignatures =-=[14,24,25,29,88]-=-.sHere, the morphologies of the fossilized calcifying bacterial colonies appear very similar to the onessof the contemporary colonies, even down to the submicrometer scale. Such fine-scale morphologic...

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... crystallographic orientation (perpendicular to cell walls) ofscrystalline phases precipitated within bacterial periplasm [61,86,87], at the cell surface or in associationswith cyanobacterial sheaths =-=[32]-=- may also promote the preservation of specific biosignatures uponsfossilization and diagenetic processes. Last, trapping of organics within minerals upon diagenesis andseven metamorphism has been show...

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...texturalsintegrity, even in the case of loosely consolidated materials [41,42], and prevents shrinkage andsdeformation of microscale to nanoscale pores, even in the case of highly sensitive materials =-=[43,44]-=-.sMilling at low Ga-ion currents has allowed preventing common artifacts like local gallium implantation,smixing of components, creation of vacancies or interstitials, creation of amorphous layers, lo...

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...f nanometers (Figure 6). The C-XANES spectrum of thesstick-like structures exhibits a main peak at 290.3 eV attributed to 1s → π* electronic transitions ofscarbon in carbonate groups (CO3) (Figure 6) =-=[58]-=- and a second absorption peak at 288.6 eV, generallysattributed to carboxylic functional groups [59]. Such C-XANES spectra have been previouslysattributed to carbonates closely associated with organic...

Citation Context

...noxygenic photosynthesis [63,79–82].s(2) Alternatively, biomineralization may occur intracellularly. Intracellular carbonate precipitation,sas recently evidenced for multiple strains of cyanobacteria =-=[73,83]-=-, may lead to the accumulation ofscalcium carbonates within bacterial cells. Whereas gas vesicles function as flotation devices insplanktonic prokaryotes [84], the precipitation of intracellular carbo...

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...n described as favoring bacterial morphologyspreservation [26,61,86]. Specific crystallographic orientation (perpendicular to cell walls) ofscrystalline phases precipitated within bacterial periplasm =-=[61,86,87]-=-, at the cell surface or in associationswith cyanobacterial sheaths [32] may also promote the preservation of specific biosignatures uponsfossilization and diagenetic processes. Last, trapping of orga...