Klymiuk, Ashley , Harper, Carla , Moore, David , Taylor, Edith , Taylor, Thomas , Krings, Michael .
Reinvestigating Carboniferous "actinomycetes": authigenic formation of biomimetic carbonates and implications for microbial paleoecology.
The microbial paleoecology of plant tissues is a field of inquiry that is gaining significant momentum, and these studies continue to offer insight into the interactions between microbes and the plants that host them and act as substrates. However, an understanding of the taphonomy and early diagensis of these associated plant materials is of critical importance when assessing putative body fossils of fungi and prokaryotes. For instance, structures associated with phloem mucilage cells of the Carboniferous fern Botryopteris tridentata have previously been describedas actinomycetes, a group of physiologically diverse high G + C Gram positive bacteria, many of which occur as enodphytes that confer resistance to pathogenic fungi. A re-examination of these Carboniferous specimens demonstrates, however, that there is little justification for considering them exemplars of filamentous actinobacteria. Instead, we suggest that these biomimetic structures (BMS) are authigenic iron carbonate minerals, formed in conjunction with the degradation of plant cell material. Luminescence (monochromatically mapped at 665 nm) observed using spinning disk confocal microscopy suggests that the diverse biomimetic morphologies present within the material were syngenetic. It is possible that minerals initially nucleated upon bacterial exopolysaccharides (EPS) or as a consequence of metabolic processes, and some of the BMS may therefore constitute bacteriogenic mineral precipitates. While there is no evidence of actinomycete remains within these specimens, they are not devoid of microbial fossils, and we re-interpret larger spherical unicells as zoosporangia of saprotrophic chytridiomycetes. As microbial substrates, degrading plant materials form complex hydrogeochemical systems. Understanding the role of saprotrophs in relation to these hydrogeochemical parameters will allow us to further understand the stages of mineralization in the early diagenesis of calcium carbonate concretions within which vascular plant remains are anatomically preserved. This study underscores the necessity of integrating geomicrobiological concepts with plant taphonomy in investigations of microbial paleoecosystems. In turn, the continuing recognition of the diversity of ancient microbes will aid in discerning taphonomic processes that lead to both information loss, and preservation, in the paleobotanical record.
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1 - University of Kansas, Ecology & Evolutionary Biology, Haworth Hall, 1200 Sunnyside Ave, Lawrence, KS, 66045, USA
2 - University Of Kansas, Ecology And Evolutionary Biology, 2041 Haworth Hall, 1200 Sunnyside Avenue, Lawrence, KS, 66045, USA
3 - University of Kansas, Center for Research and Graduate Studies, Microscopy & Analytical Imaging Center, Haworth Hall, 1200 Sunnyside Ave, Lawrence, KS, 66045, USA
4 - University Of Kansas, Department Of Ecology And Evolutionary Biology, 1200 Sunnyside Avenue, Haworth Hall, Lawrence, KS, 66045-7600, USA
5 - University Of Kansas, Department Of Ecology And Evolutionary Biology, 1200 Sunnyside Avenue, Haworth Hall, Lawrence, KS, 66045-2106, USA
6 - Department für Geo- und Umweltwissenschaften, Paläontologie und Geobiologie, Ludwig- Maximilians-Universität, Bayerische Staatssammlung für Paläontologie und Geologie, Richard-Wagner-Straße 10, Munich, 80333, Germany
Presentation Type: Oral Paper:Papers for Sections
Location: Union A/Hyatt
Date: Monday, July 9th, 2012
Time: 9:00 AM