Xing Liu1, Lingyan Huang1, Christopher Rensing1, Jie Ye1, Kenneth H Nealson2, Shungui Zhou3. 1. Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, China. 2. Department of Earth Science, University of Southern California, Los Angeles, CA, USA. sgzhou@fafu.edu.cn knealson@usc.edu. 3. Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, China. sgzhou@fafu.edu.cn knealson@usc.edu.
Abstract
In natural anoxic environments, anoxygenic photosynthetic bacteria fix CO2 by photoheterotrophy, photoautotrophy, or syntrophic anaerobic photosynthesis. Here, we describe electroautotrophy, a previously unidentified dark CO2 fixation mode enabled by the electrosyntrophic interaction between Geobacter metallireducens and Rhodopseudomonas palustris. After an electrosyntrophic coculture is formed, electrons are transferred either directly or indirectly (via electron shuttles) from G. metallireducens to R. palustris, thereby providing reducing power and energy for the dark CO2 fixation. Transcriptomic analyses demonstrated the high expression of genes encoding for the extracellular electron transfer pathway in G. metallireducens and the Calvin-Benson-Bassham carbon fixation cycle in R. palustris Given that sediments constitute one of the most ubiquitous and abundant niches on Earth and that, at depth, most of the sedimentary niche is both anoxic and dark, dark carbon fixation provides a metabolic window for the survival of anoxygenic phototrophs, as well as an as-yet unappreciated contribution to the global carbon cycle.
In natural anoxic environments, anoxygenic photosynthetic bacteria fix CO2 by photoheterotrophy, photoautotrophy, or syntrophic anaerobic photosynthesis. Here, we describe electroautotrophy, a previously unidentified dark CO2 fixation mode enabled by the electrosyntrophic interaction between Geobacter metallireducens and Rhodopseudomonas palustris. After an electrosyntrophic coculture is formed, electrons are transferred either directly or indirectly (via electron shuttles) from G. metallireducens to R. palustris, thereby providing reducing power and energy for the dark CO2 fixation. Transcriptomic analyses demonstrated the high expression of genes encoding for the extracellular electron transfer pathway in G. metallireducens and the Calvin-Benson-Bassham carbon fixation cycle in R. palustris Given that sediments constitute one of the most ubiquitous and abundant niches on Earth and that, at depth, most of the sedimentary niche is both anoxic and dark, dark carbon fixation provides a metabolic window for the survival of anoxygenic phototrophs, as well as an as-yet unappreciated contribution to the global carbon cycle.
Authors: Stefano Cestellos-Blanco; Rachel R Chan; Yue-Xiao Shen; Ji Min Kim; Tom A Tacken; Rhesa Ledbetter; Sunmoon Yu; Lance C Seefeldt; Peidong Yang Journal: Proc Natl Acad Sci U S A Date: 2022-06-21 Impact factor: 12.779