Sino-Dan international joint research team discovered a new mechanism for cable bacteria-driven biogeochemical cycling in sediments
Recently, the Institute of Microbiology, Guangdong Academy of Science, in collaboration with the School of Environmental Science and Engineering, Sun Yat-sen University, and the Center for Electromicrobiology of Aarhus University (Denmark), have made a new discovery in the study of electroactive microorganism-driven element cycling in sediments namely Electric Oxygen Extension (EOE). The EOE model proposes that overlaying water oxygen fluctuation affects distant anoxic sediment biogeochemistry mediated by cable bacteria, a recently discovered centimeter-long electro-conductive microbe. This study was published on the ISME journal entitled “Cable bacteria extend the impacts of elevated dissolved oxygen into anoxic sediments” on Jan. 21st, 2021 (https://doi.org/10.1038/s41396-020-00869-8).
Profound biogeochemical responses of anoxic sediments to the fluctuation of dissolved oxygen (DO) in overlaying water are often observed, despite oxygen having a limited permeability in sediments. This contradiction is indicative of previously unrecognized mechanism that bridging the oxic and anoxic sediment layers. Using sediments from an urban river suffering from long-term polycyclic aromatic hydrocarbons (PAHs) contamination, the research team analyzed the physicochemical and microbial responses to artificially elevated dissolved oxygen (eDO) in the overlying water over nine weeks of incubation. Significant changes in key environmental parameters and microbial diversity were detected over the 0-6 cm sediment depth, along with accelerated degradation of PAHs, despite that eDO only increased the porewater DO in the millimeter subfacial layer. The dynamics of physicochemical and microbial properties coincided well with significantly increased presence of sulfide-oxidizing cable bacteria filaments under eDO, and were predominantly driven by cable bacteria metabolic activities. Phylogenetic ecological network analyses further revealed that eDO reinforced cable bacteria associated inter-specific interactions with functional microorganisms such as sulfate reducers, PAHs-degraders, and electroactive microbes, suggesting enhanced microbial syntrophy taking advantage of cable bacteria metabolism for the regeneration of SO42- and long-distance electron transfer. Thereby, these results suggest cable bacteria may mediate the impacts of eDO in anaerobic sediments by altering sediment physiochemical properties and by reinforcing community interactions.
This newly discovered electric oxygen extension (EOE) mechanism would greatly advance researches in in-situ bioremediation of sediments. Grants from several agencies have supported this research including the NSFC Major Research Plan: Mechanisms Underlining Elemental Cycling on the Earth by Microbes in Hydrosphere (key project), Guangdong Provincial Programs for Science and Technology Development, GDAS’ Special Project of Science and Technology Development, and Guangdong MEPP Fund.