The Fossil Record of Microbial Life

Knoll, Andrew H.

doi:10.1002/9781118280874.ch16

Cited by 19 publications

(9 citation statements)

References 111 publications

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“…Hydrothermal vents have been suggested as the probable environments within which life may have originated [ 5 – 7 ], and microbial fossils, in addition to stromatolites considered to be fossil microbial mats, constitute the earliest morphological evidence for life on Earth [ 8 – 10 ]. Many of the oldest proposed microbial fossils occur within hydrothermally influenced settings [ 11 – 13 ], yet microbial fossils from ancient high-temperature vents are extremely rare [ 14 , 15 ].…”

Section: Introductionmentioning

confidence: 99%

Microbial-tubeworm associations in a 440 million year old hydrothermal vent community

et al. 2018

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Microorganisms are the chief primary producers within present-day deep-sea hydrothermal vent ecosystems, and play a fundamental role in shaping the ecology of these environments. However, very little is known about the microbes that occurred within, and structured, ancient vent communities. The evolutionary history, diversity and the nature of interactions between ancient vent microorganisms and hydrothermal vent animals are largely undetermined. The oldest known hydrothermal vent community that includes metazoans is preserved within the Ordovician to early Silurian Yaman Kasy massive sulfide deposit, Ural Mountains, Russia. This deposit contains two types of tube fossil attributed to annelid worms. A re-examination of these fossils using a range of microscopy, chemical analysis and nano-tomography techniques reveals the preservation of filamentous microorganisms intimately associated with the tubes. The microfossils bear a strong resemblance to modern hydrothermal vent microbial filaments, including those preserved within the mineralized tubes of the extant vent polychaete genus Alvinella. The Yaman Kasy fossil filaments represent the oldest animal–microbial associations preserved within an ancient hydrothermal vent environment. They allude to a diverse microbial community, and also demonstrate that remarkable fine-scale microbial preservation can also be observed in ancient vent deposits, suggesting the possible existence of similar exceptionally preserved microfossils in even older vent environments.

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Section: Introductionmentioning

confidence: 99%

Microbial-tubeworm associations in a 440 million year old hydrothermal vent community

et al. 2018

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“…At least some Archean microstructures could be nonbiological features that reflect hydrothermal alteration and associated migration of organic carbon (e.g., Brasier et al 2005;Sforna et al 2014). Migrating organics can be adsorbed onto mineral grains, and this is clearly evident in early Archean cherts (Knoll 2012); spheroidal and solid filamentous structures can also selforganize during metamorphism. Careful investigation shows that some Archean cherts contain multiple generations of silica and organic matter, underscoring the need for caution in paleobiological interpretation (Marshall et al 2012).…”

Section: Problems Of Archean Paleobiologymentioning

confidence: 99%

Paleobiological Perspectives on Early Microbial Evolution

Knoll

2015

Cold Spring Harb Perspect Biol

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Microfossils, stromatolites, and chemical biosignatures indicate that Earth became a biological planet more than 3.5 billion years ago, making most of life's history microbial. Proterozoic rocks preserve a rich record of cyanobacteria, including derived forms that differentiate multiple cell types. Stromatolites, in turn, show that microbial communities covered the seafloor from tidal flats to the base of the photic zone. The Archean record is more challenging to interpret, particularly on the question of cyanobacterial antiquity, which remains to be resolved. In the late Neoproterozoic Era, increasing oxygen and radiating eukaryotes altered the biosphere, with planktonic algae gaining ecological prominence in the water column, whereas seaweeds and, eventually, animals spread across shallow seafloors. From a microbial perspective, however, animals, algae, and, later, plants simply provided new opportunities for diversification, and, to this day, microbial metabolisms remain the only essential components of biogeochemical cycles.

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“…This approach provides information on both the absolute timescale and the relative variation of the evolutionary rates across the phylogeny (Fig.1a). Yet, because most life is microbial, and most microbes do not leave discernable fossils, major uncertainties remain about the ages of microbial groups and the timing of some of the earliest and most important events in life's evolutionary history6,7.…”

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confidence: 99%

Gene transfers can date the tree of life

et al. 2018

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Biodiversity has always been predominantly microbial and the scarcity of fossils from Bacteria, Archaea and microbial Eukaryotes has prevented a comprehensive dating of the tree of life. Here we show that patterns of lateral gene transfer deduced from the analysis of modern genomes encode a novel and abundant source of information about the temporal coexistence of lineages throughout the history of life. We use state-of-the-art species tree aware phylogenetic methods to reconstruct the history of thousands of gene families and demonstrate that dates implied by gene transfers are consistent with estimates from relaxed molecular clocks in Bacteria, Archaea and Eukaryotes. We present the order of speciations according to LGT calibrated to geological time for three datasets comprised of 40 genomes for Cyanobacteria, 60 genomes for Archaea and 60 genomes for Fungi. An inspection of discrepancies between transfers and clocks and a comparison with mammal fossils show that gene transfer in microbes is potentially as informative for dating the tree of life as the geological record in macroorganisms.

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The Fossil Record of Microbial Life

Cited by 19 publications

References 111 publications

Microbial-tubeworm associations in a 440 million year old hydrothermal vent community

Microbial-tubeworm associations in a 440 million year old hydrothermal vent community

Paleobiological Perspectives on Early Microbial Evolution

Gene transfers can date the tree of life

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