Carbonaceous Filaments Research Articles

Rapid colonization of a space‐returned Ryugu sample by terrestrial microorganisms

AbstractThe presence of microorganisms within meteorites has been used as evidence for extraterrestrial life, however, the potential for terrestrial contamination makes their interpretation highly controversial. Here, we report the discovery of rods and filaments of organic matter, which are interpreted as filamentous microorganisms, on a space‐returned sample from 162173 Ryugu recovered by the Hayabusa 2 mission. The observed carbonaceous filaments have sizes and morphologies consistent with microorganisms and are spatially associated with indigenous organic matter. The abundance of filaments changed with time and suggests the growth and decline of a prokaryote population with a generation time of 5.2 days. The population statistics indicate an extant microbial community originating through terrestrial contamination. The discovery emphasizes that terrestrial biota can rapidly colonize extraterrestrial specimens even given contamination control precautions. The colonization of a space‐returned sample emphasizes that extraterrestrial organic matter can provide a suitable source of metabolic energy for heterotrophic organisms on Earth and other planets.

Comment on “Biogenicity of Earth's earliest fossils: a resolution of the controversy” by J. William Schopf and Anatoliy B. Kudryavtsev, Gondwana Research 22 (2012), 761–771

Recently, Schopf and Kudryavtsev (2012) have published an exhaustive review on the biogenicity of the most controversial evidence of ancient life on Earth to date: an assemblage of carbonaceous filaments found in the ~3465 Ma Apex chert of northwestern Australia (Schopf and Packer, 1987; Schopf, 1993). The morphology of the filaments, their carbon isotopic composition and the sedimentary environment interpreted as shallow marine, suggested to Schopf (1993) that these filaments were fossilized cyanobacteria. This discovery sparkled a large controversy among the scientific community that lasted for more than 25 years (see Pinti and Altermann, 2011 for a review on the subject). In the synopsis of the controversy (page 762), Schopf andKudryavtsev (2012) wrote: “the Apex fossils have subsequently been suggested to be”... “inorganic silica or clay mineral needle-like crystals (Pinti et al., 2009)”. Again at page 769, the authors reported that “Needles composed of halloysite (Al2Si2O5[OH]4), a clay mineral, and of quartz (SiO2), have been compared with the Apex fossils (Pinti et al., 2009)”. These are two serious misstatements because we never compared any of the pseudofossils that we observed in Apex chert to the microfossils of Schopf (1993). Schopf and Kudryavtsev (2012) themselves report at

Microfossil assemblage from the 3400 Ma Strelley Pool Formation in the Pilbara Craton, Western Australia: Results form a new locality

A new microfossil locality for the ca. 3400Ma Strelley Pool Formation (SPF), in the Pilbara Craton, Western Australia, was discovered in the Panorama greenstone belt. Large and morphologically diverse microfossils (>20μm, up to 100μm, along the major dimension) are abundant in a carbonaceous laminated black chert of shallow water origin that was originally collected in 2010 and relocated in 2011 just south of the Trendall Reserve (State Geoheritage Reserve, R50149). Over 300 small, spherical and lenticular (flanged and non-flanged lenses) carbonaceous cellular microfossils are present in each replicated thin section measuring 2.5cm×3.4cm. In addition, film-like structures and tubular filaments were discovered. Narrow carbonaceous filaments of several types are also present in and around the secondary cavity-fill cherts, although their biogenicity is uncertain. Colonies of spherical and lenticular structures are often observed. Colonies composed of small spheroids can be classified into at least two groups based on the sizes of the individuals. Their mode of clustering is variable, ranging from tight to loose and from spherical to random. Colonies of lenticular structures are often composed of a mixture of flanged and non-flanged lenses, in addition to those solely composed of either flanged or non-flanged lenses. The size ranges of these three types are not statistically distinguishable. Therefore, it is currently unknown whether flanged and non-flanged lenses represent different species or different life stages of the same species. Although more research will be needed to establish the taxonomic framework for these ancient microfossils, they provide evidence that the coastal region of the 3.4Ga “Strelley Pool Sea” was inhabited by various microbial communities, reflecting the early stage diversification of life on Earth.

Ni- and Fe-based catalysts for hydrogen and carbon nanofilament production by catalytic decomposition of methane in a rotary bed reactor

Four catalysts, consisting of Ni, Ni:Cu, Fe or Fe:Mo as the active phase and Al 2O 3 or MgO as a textural promoter, were tested for the catalytic decomposition of methane in a rotary bed reactor, obtaining both CO 2-free hydrogen and carbon nanostructures in a single step. Hydrogen yields of up to 14.4 Ndm 3 H 2·(h·g cat) − 1 were obtained using the Ni-based catalysts, and methane conversions above 80% were observed with the Fe-based catalysts. In addition to hydrogen production, the Ni-based catalysts allowed the large-scale production of fishbone-like carbon nanofibres, whereas the use of the Fe-based catalysts promoted the production of carbonaceous filaments having a high degree of structural order, consisting of both chain-like carbon nanofibres and carbon nanotubes.

Erratum: Hydrothermal alteration and microfossil artefacts of the 3,465-million-year-old Apex chert

The earliest fossils of cyanobacteria have been controversially reported from the 3,465-million-year-old Apex chert in Western Australia. Mineralogical analyses of the rock near the fossil site indicate that the site experienced repeated alterations at low and medium temperatures, and is therefore unlikely to have preserved any early forms of life. The 3,465-million year-old Apex chert of the Pilbara Craton in Western Australia has been controversially reported to contain some of the oldest fossil evidence for life: tiny carbonaceous filaments interpreted as cyanobacteria1. Yet, on the basis of the presence of barite and native metals, it has been suggested that the chert formed from hydrothermal fluids at temperatures greater than 250 ∘C (refs 2, 3), an unlikely environment for cyanobacteria. Here we use scanning electron microscopy to assess the mineralogy and depositional setting of the chert veins surrounding the nodes that contain the microfossils. In addition to rare native metals, we find an assemblage of iron oxides and clay minerals, which we interpret to have formed during repeated pulses of hydrothermal alteration at low to medium temperatures. We also find micrometre-sized silica structures that resemble microbial exopolymers4, and textures formed by the partial dissolution of tubular minerals that look similar to fossilized microbial mats5. Other branched microstructures suggest post-depositional colonization of microcracks and fissures by microbes5. These observations are not directly applicable to the carbonaceous filaments purported to be the earliest fossil evidence of life, as we did not recover any in our sample. However, because of the observed hydrothermal and groundwater alteration, we conclude that the Apex chert is unlikely to have preserved any early forms of life.

Microbial weathering of Fe-rich phyllosilicates and formation of pyrite in the dolomite precipitating environment of a Miocene lacustrine system

Sedimentary sequences composed of selenite gypsum, mudstone, and dolomite microbialites cropping out in the eastern part of the Madrid Basin were deposited in a mudflat – saline-lake system during the Miocene. In some dolomite beds enriched in detrital grains, dolomite crystals occur intergrown with framboidal pyrite clusters that in many cases are arranged along the associated phyllosilicate cleavages, which accounts for the mineral disaggregation, and eventually for the mineral replacement. High-resolution FE-SEM investigations across the interface between the pyrite and the phyllosilicate show that a single phyllosilicate is replaced by iron sulphides in different microsites, with retention of some aspects of the parent structure. Pyrite formed in the sediment as texturally complex framboids, coexisting with amorphous to poorly crystalline iron-rich sulphide phases, and include carbonaceous filaments with biogenic isotopic signatures (δ13C = −22.95‰). Microprobe analytical data indicate the weathered phyllosilicates to be significantly depleted in Fe relative to Si and Al. The selective release of Fe has not involved the mineral transformation to secondary phyllosilicates, which suggests a preferential microbial colonization of the Fe-bearing minerals rather than a thermodynamically driven degradation of those minerals. Depleted δ34S values in pyrite further suggest that sulphate microbial reduction to sulphide was active within the sediment during the alteration of the silicates. This paper gives new insight into the microbial weathering of phyllosilicates and the subsequent formation of pyrite through a sequence of intermediate products enriched in iron. These processes were coeval with the microbially-mediated precipitation of dolomite, which further reinforces the role of the microbes in the formation of the sulphides.

On CH 4 decomposition during separation from H 2 mixtures with thin Pd membranes

The influence of high CH 4 concentrations (8–31%) on the H 2 permeation through a 2 μm thick Pd membrane was investigated between 473 and 823 K at 100 kPa pressure difference at the maximum H 2 extraction limit, with the retentate H 2 concentration always staying above 50%. The permeate flux was slightly higher in CH 4/H 2 mixtures than in equimolar N 2/H 2 mixtures. This is attributed to decomposition of CH 4 on the Pd surface as indicated by trace amounts of C 2H 6. At 723 K and below H 2 permeation remained stable during 6 h experiments in CH 4/H 2 mixtures, whereas it gradually decreased with time above that threshold. TPO, SEM and XRD revealed several types of carbon forming on the surface of membrane pieces during exposure to pure CH 4. Following CH 4 treatment below 723 K two types of carbon deposits were found, which are designated as carbidic carbon and disordered carbon aggregates. Carbonaceous filaments were observed after CH 4 exposure above 723 K and graphite platelets after treatment at 823 K. Furthermore, metastable Pd 0.9C 0.1 and/or Pd 0.85C 0.15 phases were detected after CH 4 treatment at 573, 623, and 773 K. Carbidization of the membrane was most severe at 623 K, but the carbides could be readily decomposed by heat treatment in N 2 between 623 and 723 K. Mechanisms for deactivation of the Pd membrane during separation of CH 4/H 2 mixtures at elevated temperatures are discussed.

Micro-scale variations of iron isotopes in fossilized microorganisms

AbstractLaser-ablation inductively coupled plasma mass spectroscopy analyses have been performed on carbonaceous filamentous structures that have been interpreted as fossilized microorganisms containing ~10–50 wt% Fe and on non-carbonaceous filamentous structures that have been interpreted to have been formed abiotically containing ~80 wt% Fe. The obtained laser-ablation profiles of the two structural types show a distinct difference in the iron isotopic variations. The centers of the carbonaceous filaments are enriched in 57Fe and 58Fe and depleted in 56Fe. The surficial parts of the filaments display an opposite behavior of the iron isotopes and are thus enriched in 56Fe and depleted in 57Fe and 58Fe. 54Fe usually follows 57Fe and 58Fe but in some cases it follows 56Fe instead. The outer, surficial parts enriched in 56Fe have been interpreted as iron oxides precipitated on the surfaces of the microorganisms as they mediate oxidation of the iron to achieve metabolic energy. The laser-ablation profiles of the abiotically formed non-carbonaceous filamentous structures do not show the same characteristics as the carbonaceous filaments but only irregular elevations of 56Fe. The characteristic profile patterns of the isotope variations in the microfossils suggest that microbially formed iron oxides may be enriched in 56Fe. If that is the case the isotopic profiles could be used to distinguish abiotically formed iron oxides from biologically formed oxides.

Carbon Isotopic Signatures of Individual Archean Microfossils(?) from Western Australia

New types of carbonaceous filamentous microstructures have been identified in silica veins at two new localities in the ∼3.5 Ga North Pole area of Western Australia. Their carbon isotopic compositions were measured in situ by secondary-ion mass spectrometry. The carbonaceous filaments are ∼1μm wide, 10 to 100 μm long, and are permineralized in a fine-grained (∼1 μm) silica matrix. They are morphologically divided into three types (i.e., spiral, threadlike, and branched filaments). Their sizes and morphologies resemble modern and previously reported fossil bacteria. These similarities and their complex three-dimensional geometry suggest that they may represent morphologically preserved fossil bacteria. δ13C values of the carbonaceous filaments range from −42 to −32‰, which strongly suggest that they are composed of biologically fixed organic compounds, possibly via the reductive acetyl-CoA pathway or the Calvin cycle. This is consistent with the hypothesis that autotrophs already existed on the Archean Earth.

Model parametric Hamiltonians and bonding theoretical tools in simulation of catalytic reaction steps. Hydrotreatment of oil components

Quantum chemistry calculations of hydrocarbons components and hydrogen have been carried out using model surface adsorption sites on aggregates and model parametric Hamiltonians. Bader's topological analysis of the charge density in the valence region is used to describe the adsorption site on which reactions may occur. A description of the adsorbate and surface bindings with diatomic binding energies (DBE) and orbital interactions are presented. Chemisorption and hydrogenation reactions of molecular fragments that are intermediates in hydrocarbon formation on a nickel aggregate were calculated. Also, the growing of hydrocarbon chains and the building of carbonaceous filaments were studied. The modeling of hydrogen dissociation on HDS catalyst was analyzed. In addition, the hydrogenation step of the HDN reaction on a modeled MoS 2 catalyst, employing pyridine as model molecule, is presented.

Neoproterozoic rocks of the Newfoundland Avalon Zone

A ca. 15 km thick succession of volcanic and sedimentary Neoproterozoic rocks are exposed within the Avalon Terrane of Newfoundland. Petrologic and geochemical study of volcanic suites and sedimentological analyses indicate that most deposition took place in ensialic rift basins and associated continental arc settings. On the Avalon Peninsula, over 7500 m of volcaniclastic strata include initial submarine fan and slope deposits, which pass upward into a prograded wedge of deltaic and fluvial deposits. This flysch-to-molasse transition, and associated folding and volcanism, mark the Neoproterozoic Avalonian Orogeny. Post-orogenic erosion was followed by deposition of extensive Cambrian siliciclastic deposits. Recent U Pb zircon dating of many of the Neoproterozoic volcanic units provides some constraints on both intra-Avalon and global correlations. More precise dates are needed to improve correlation and better constrain the geologic history of this region. Glaciogenic diamictites of the Gaskiers Formation exposed on the Avalon Peninsula may eventually also prove useful for global correlation. Biostratigraphic study of the latest Neoproterozoic-Lower Cambrian deposits has resulted in ratification of the Precambrian-Cambrian Boundary Stratotype in an exposure on the Burin Peninsula. Older Neoproterozoic rocks contain well-preserved Ediacara-type fossils and a low-diversity suite of microfossils including acritarchs and carbonaceous filaments, the latter of which have little biostratigraphic utility. Aside from work on the Precambrian-Cambrian boundary section, little or no chemostratigraphic, magnetostratigraphic or sequence stratigraphic work has been completed on the Neoproterozoic of the Newfoundland Avalon Terrane.

Carbonaceous filaments from North Pole, Western Australia: Are they fossil bacteria in archean stromatolites? A discussion

Abstract A sample of chert from North Pole in the Archaean Pilbara block of Western Australia contains carbonaceous filaments that resemble microfossils. These occur in alternating light and dark laminae that look stromatolitic. However, the filaments are too simple in form for their origin to be determined, so they should be regarded as dubiofossils, perhaps biogenic, perhaps inorganic. Their host laminae were inorganically precipitated in a concordant fissure and thus cannot be stromatolitic. This fissure is younger than the surrounding silicified sediments of the ca. 3500 Ma old Warrawoona Group and possibly formed towards the end of the uplift and associated fracturing of the North Pole Dome, perhaps ca. 2750 Ma ago. The filaments are therefore contaminants in secondary chert. The filament-bearing rock was collected less than a metre from one of the localities (B) from which Awramik et al. reported early Archaean microfossils and possible microfossils. Their filaments from this locality were almost identical to those described here and were found in similar laminae. This suggests that their locality B filaments may also be contaminants in secondary chert. Other filaments found by Awramik et al. at North Pole come from an imprecisely located sample site (locality A) where the rock relationships are unknown. Since the host laminae of these filaments are not demonstrably primary and as cryptic concordant fissures filled with secondary minerals are common in locality A rocks, the filaments from this sample site could be contaminants too. Those that were assigned to Archaeotrichion should be treated as dubiofossils. Thus, the filaments described by Awramik et al. may not be fossil bacteria in ca. 3500 Ma old stromatolites, as they proposed, and are not necessarily the oldest known fossil organisms, as has been claimed.

Simulation of the behavior of supported metal catalysts in real reaction atmospheres by means of model catalysts

Model catalysts formed of small crystallites of Ni, Co, or Fe supported on thin, electron transparent films of nonporous alumina were heated in chemical atmospheres having compositions in the range encountered in the steam-reforming reaction. Electron microscopy and electron diffraction were used to investigate the physical and chemical changes that occurred. For a better understanding of the phenomena involved, the effect of the mixture is compared to the effects caused by the individual components and by their combinations. It is shown that, depending upon the nature of the catalyst as well as upon the composition of the mixture, sintering or/and coking can occur much more rapidly in mixtures than in single-component atmospheres. This suggests that a cooperative action of the reaction components is the cause of the early deactivation of the steam-reforming catalysts. Various phenomena such as carbon deposition (as films or patches on the surface of the catalyst and on the substrate or as filaments), deformation of the crystallites, severe sintering, and permanent loss of metal to the gas stream were observed. Explanations are provided for the behavior of the Ni Al 2O 3 , Co Al 2O 3 , and Fe Al 2O 3 catalysts, in various atmospheres, by considering the competition between carbon deposition and its gasification, as well as the strength of the interactions between crystallites and substrate. Two kinds of filaments were observed: carbonaceous filaments and metal oxide filaments which probably contain some carbon. A thermodynamic condition for the formation of filamentous carbon is suggested. If the sum of the interfacial free energies between carbon and crystallite, and carbon and substrate is smaller than that between crystallite and substrate, then carbon could penetrate between crystallites and substrate and filaments would be generated. Indeed, carbonaceous filaments were identified only when the catalyst particles were present as metals. In such cases, the interfacial free energy between the metal crystallite and alumina is much greater than that between the oxidized metal and alumina and the above thermodynamic condition is more likely to be satisfied. Permanent loss of active metal to the gas stream occurred, either because of the disintegration of the crystallites caused by carbon precipitation inside the particles, and/or possibly because of the formation of volatile Carbonyls.

Carbonaceous filaments from North Pole, Western Australia: Are they fossil bacteria in Archaean stromatolites?

Carbonaceous filaments from North Pole, Western Australia: Are they fossil bacteria in Archaean stromatolites?

Significance of diagenesis for the origin of Witwatersrand-type uraniferous conglomerates

A petrographic study of pyrite may be the key to the understanding of the Witwatersrand (South Africa) gold-uranium deposits: the sediments of the Witwatersrand Supergroup contain at least nine types of pyrite, namely (1) Laminated pyrite seams; (2) pyrite nodules in shales; (3) pyrite nodules in quartzite and conglomerate; (4) pyrite as overgrowths on carbonaceous filaments; (5) pyrite filling pore spaces and replacing clasts; (6) pyrite replacing detrital magnetite; (7) allogenic fragments of laminated pyrite; (8) allogenic fragments of pyrite nodules; and (9) allogenic fragments of coarse-grained pyrite. Types 1-6 probably formed during diagenesis of the sediment due to the activity of sulphate-reducing bacteria; types 7 and 8 are transported fragments of diagentic pyrite; type 9 may be of diverse origin, but may also in part be transported fragments of diagenetic pyrite. Pyrite petrography suggests a multi-stage history of ore enrichment: diagenetic precipitation of gold, uraninite and pyrite in sediments containing organic matter, followed by erosion, transport of allogenic fragments of ore minerals for short distances, and concentration in lag gravels at channel bottoms and unconformities. Repeated cycles of weathering, diagenetic precipitation from weathering solutions, erosion, minor transport and redeposition may have caused the extraordinary enrichment of the ores on major unconformities in the Upper Witwatersrand Supergroup.