Taphonomy of Silicified Filamentous Microbes in Modern Geothermal Sinters--Implications for Identification

Jones, Brian; Renaut, Robin W.; Rosen, Michael R.

doi:10.1669/0883-1351(2001)016<0580:tosfmi>2.0.co;2

Cited by 87 publications

(48 citation statements)

References 35 publications

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“…As used here, ''silicified microbes'' refer to any microorganisms (bacteria, archaea, fungi) that have been preserved through replacement of their organic soft parts by opal-A, and/or have been externally encrusted with opal-A (Jones et al 1997(Jones et al , 2001.…”

Section: Terminologymentioning

confidence: 99%

Impact of Seasonal Changes on the Formation and Accumulation of Soft Siliceous Sediments on the Discharge Apron of Geysir, Iceland

Jones¹,

Renaut²

2010

Journal of Sedimentary Research

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Unconsolidated, highly porous, permeable siliceous sediments found in shallow-water pools on the middle and distal parts of Geysir's discharge apron are formed of cryogenic opal-A (COA), opal-A spheres, opal-A cement, silicified microbes, and detrital lithic grains. Silicified leaves and silica-coated grass stems and twigs are locally present with these pool sediments, and microbial mats commonly cover the sediment surface. Partially consolidated layers (, 0.5 cm thick) form when the constituent grains are bound together by filamentous microbes, exopolysaccharides, and/or opal-A cement. Most components of the sediment can be related to processes that are controlled largely by seasonal variations. Low temperatures in winter promote freezing of the medial to distal discharge waters and lead to formation of COA in ice. When the ice melts, the released COA grains become part of the pool sediments. Microbial mats trap and bind sediment and provide templates for silica precipitation during spring and summer, but become (semi-)dormant during the constant darkness that Iceland experiences during winter. When the waters are sufficiently supersaturated, opal-A precipitates as spheres in the water column and cement in pool deposits. In some pools, seasonal changes are evident from the alternation of ''soft'' and ''hard'' (partly cemented) laminae. Elsewhere, however, the distinction between the different time-dependent components is lost because they become superimposed on each other or as aperiodic changes in flow patterns affect different pools.

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Section: Terminologymentioning

confidence: 99%

Impact of Seasonal Changes on the Formation and Accumulation of Soft Siliceous Sediments on the Discharge Apron of Geysir, Iceland

Jones¹,

Renaut²

2010

Journal of Sedimentary Research

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“…The former described fossilization in hot spring systems (e.g., cyanobacteria or anoxygenic photosynthetic bacteria) with studies following the early phases of fossilization (Phoenix et al 2000;Schultze-Lam et al 1995) through to the final silicified remains (Cady and Farmer 1996;Handley et al 2005Handley et al , 2008Konhauser and Ferris 1996;Konhauser et al 2001;Jones et al 1998Jones et al , 2001Jones et al , 2003Jones et al , 2004Mountain et al 2003;SchultzeLam et al 1995;Tobler et al 2008;Walter et al 1972).…”

Section: Introductionmentioning

confidence: 99%

Experimental fossilization of the Thermophilic Gram-positive BacteriumGeobacillusSP7A: A Long Duration Preservation Study

Orange

Dupont

Goff

et al. 2014

Geomicrobiology Journal

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Recent experiments to fossilize microorganisms using silica have shown that the fossilization process is far more complex than originally thought; microorganisms not only play an active role in silica precipitation but may also remain alive while silica is precipitating on their cell wall. To better understand the mechanisms that lead to the preservation of fossilized microbes in recent and ancient rocks, we experimentally silicified a Gram-positive bacterium, Geobacillus SP7A, over a period of five years. The microbial response to experimental fossilization was monitored with the use of LIVE/DEAD staining to assess the structural integrity of the cells during fossilization. It documented the crucial role of silicification on the preservation of the cells and of their structural integrity after several years. Electron microscopy observations showed that initial fossilization of Gram-positive bacteria was extremely rapid, thus allowing very good preservation of Geobacillus SP7A cells. A thick layer of silica was deposited on the outer surface of cell walls in the earliest phase of silicification before invading the cytoplasmic space. Eventually, the cell wall was the only recognizable feature. Heavily mineralized cells thus showed morphological similarities with natural microfossils found in the rock record.

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“…As most Precambrian prokaryotic fossils have been found in siliceous sedimentary rocks, silicification would be important for three-dimensional preservation of microfossil morphology (e.g., Schopf & Walter, 1983). Silicification processes of microbes have been reported by observation of modern hydrothermal systems (e.g., Jones, Renaut, & Rosen, 2001;Konhauser, Phoenix, Bottrell, Adams, & Head, 2001). The microbial role during their own silicification has also been a topic of debate (e.g., Benning, Phoenix, Yee, & Konhauser, 2004;Benning, Phoenix, Yee, & Tobin, 2004;Konhauser, Jones, Phoenix, Ferris, & Renaut, 2004;Yee, Phoenix, Konhauser, Benning, & Ferris, 2003).…”

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confidence: 99%

Changes of aliphatic C–H bonds in cyanobacteria during experimental thermal maturation in the presence or absence of silica as evaluated by FTIR microspectroscopy

et al. 2018

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Aliphatic C-H bonds are one of the major organic signatures detected in Proterozoic organic microfossils, and their origin is a topic of interest. To investigate the influence of the presence of silica on the thermal alteration of aliphatic C-H bonds in prokaryotic cells during diagenesis, cyanobacteria Synechocystis sp. PCC6803 were heated at temperatures of 250-450°C. Changes in the infrared (IR) signals were monitored by micro-Fourier transform infrared (FTIR) spectroscopy. Micro-FTIR shows that absorbances at 2,925 cm band (aliphatic CH ) and 2,960 cm band (aliphatic CH ) decrease during heating, indicating loss of the C-H bonds, which was delayed by the presence of silica. A theoretical approach using solid-state kinetics indicates that the most probable process for the aliphatic C-H decrease is three-dimensional diffusion of alteration products under both non-embedded and silica-embedded conditions. The extrapolation of the experimental results obtained at 250-450°C to lower temperatures implies that the rate constant for CH (k ) is similar to or lower than that for CH (k ; i.e., CH decreases at a similar rate or more slowly than CH ). The peak height ratio of 2,960 cm band (CH )/2,925 cm band (CH ; R values) either increased or remained constant during the heating. These results reveal that the presence of silica does affect the decreasing rate of the aliphatic C-H bonds in cyanobacteria during thermal maturation, but that it does not significantly decrease the R values. Meanwhile, studies of microfossils suggest that the R values of Proterozoic prokaryotic fossils from the Bitter Springs Group and Gunflint Formation have decreased during fossilization, which is inconsistent with the prediction from our experimental results that R values did not decrease after silicification. Some process other than thermal degradation, possibly preservation of specific classes of biomolecules with low R values, might have occurred during fossilization.

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Taphonomy of Silicified Filamentous Microbes in Modern Geothermal Sinters--Implications for Identification

Cited by 87 publications

References 35 publications

Impact of Seasonal Changes on the Formation and Accumulation of Soft Siliceous Sediments on the Discharge Apron of Geysir, Iceland

Impact of Seasonal Changes on the Formation and Accumulation of Soft Siliceous Sediments on the Discharge Apron of Geysir, Iceland

Experimental fossilization of the Thermophilic Gram-positive BacteriumGeobacillusSP7A: A Long Duration Preservation Study

Changes of aliphatic C–H bonds in cyanobacteria during experimental thermal maturation in the presence or absence of silica as evaluated by FTIR microspectroscopy

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