Oxygen-Dependent Morphogenesis of Modern Clumped Photosynthetic Mats and Implications for the Archean Stromatolite Record

Geosciences

Min Sub Sim³  Biqing Liang³  Alexander P. Petroff³  Alexander Evans³  Vanja Klepac-Ceraj²  David T. Flannery¹  Malcolm R. Walter¹ 

[1] Australian Centre for Astrobiology, School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW 2052, Australia;;Applied Molecular Photomedicine Laboratory, The Forsyth Institute, Cambridge, MA 02142, USADepartment of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA;

关键词: stromatolite;    oxygen;    photosynthesis;    cyanobacteria;    morphogenesis;    Archean;    evolution;   

DOI  :  10.3390/geosciences2040235

来源: mdpi

【 摘 要 】

Some modern filamentous oxygenic photosynthetic bacteria (cyanobacteria) form macroscopic tufts, laminated cones and ridges that are very similar to some Archean and Proterozoic stromatolites. However, it remains unclear whether microbes that constructed Archean clumps, tufts, cones and ridges also produced oxygen. Here, we address this question by examining the physiology of cyanobacterial clumps, aggregates ~0.5 mm in diameter that initiate the growth of modern mm- and cm-scale cones. Clumps contain more particulate organic carbon in the form of denser, bowed and bent cyanobacterial filaments, abandoned sheaths and non-cyanobacterial cells relative to the surrounding areas. Increasing concentrations of oxygen in the solution enhance the bending of filaments and the persistence of clumps by reducing the lateral migration of filaments away from clumps. Clumped mats in oxic media also release less glycolate, a soluble photorespiration product, and retain a larger pool of carbon in the mat. Clumping thus benefits filamentous mat builders whose incorporation of inorganic carbon is sensitive to oxygen. The morphogenetic sequence of mm-scale clumps, reticulate ridges and conical stromatolites from the 2.7 Ga Tumbiana Formation likely records similar O₂-dependent behaviors, preserving currently the oldest morphological signature of oxygenated environments on Early Earth.

【 授权许可】

CC BY   
© 2012 by the authors; licensee MDPI, Basel, Switzerland.