Enrichment of Marinobacter sp. and Halophilic Homoacetogens at the Biocathode of Microbial Electrosynthesis System Inoculated With Red Sea Brine Pool
AuthorsAlQahtani, Manal Faisal
Ragab, Alaa I.
KAUST DepartmentEnvironmental Science and Engineering Program
Water Desalination and Reuse Research Center (WDRC)
King Abdullah University of Science and Technology, Water Desalination and Reuse Center, Biological and Environmental Science and Engineering Division, Thuwal, Saudi Arabia
Biological and Environmental Sciences and Engineering (BESE) Division
KAUST Grant NumberURF/1/2985-01-01
Permanent link to this recordhttp://hdl.handle.net/10754/660090
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AbstractHomoacetogens are efficient CO2 fixing bacteria using H2 as electron donor to produce acetate. These organisms can be enriched at the biocathode of microbial electrosynthesis (MES) for electricity-driven CO2 reduction to acetate. Studies exploring homoacetogens in MES are mainly conducted using pure or mix-culture anaerobic inocula from samples with standard environmental conditions. Extreme marine environments host unique microbial communities including homoacetogens that may have unique capabilities due to their adaptation to harsh environmental conditions. Anaerobic deep-sea brine pools are hypersaline and metalliferous environments and homoacetogens can be expected to live in these environments due to their remarkable metabolic flexibility and energy-efficient biosynthesis. However, brine pools have never been explored as inocula for the enrichment of homacetogens in MES. Here we used the saline water from a Red Sea brine pool as inoculum for the enrichment of halophilic homoacetogens at the biocathode (−1 V vs. Ag/AgCl) of MES. Volatile fatty acids, especially acetate, along with hydrogen gas were produced in MES systems operated at 25 and 10% salinity. Acetate concentration increased when MES was operated at a lower salinity ∼3.5%, representing typical seawater salinity. Amplicon sequencing and genome-centric metagenomics of matured cathodic biofilm showed dominance of the genus Marinobacter and phylum Firmicutes at all tested salinities. Seventeen high-quality draft metagenome-assembled genomes (MAGs) were extracted from the biocathode samples. The recovered MAGs accounted for 87 ± 4% of the quality filtered sequence reads. Genome analysis of the MAGs suggested CO2 fixation via Wood–Ljundahl pathway by members of the phylum Firmicutes and the fixed CO2 was possibly utilized by Marinobacter sp. for growth by consuming O2 escaping from the anode to the cathode for respiration. The enrichment of Marinobacter sp. with homoacetogens was only possible because of the specific cathodic environment in MES. These findings suggest that in organic carbon-limited saline environments, Marinobacter spp. can live in consortia with CO2 fixing bacteria such as homoacetogens, which can provide them with fixed carbon as a source of carbon and energy.
CitationAlqahtani, M. F., Bajracharya, S., Katuri, K. P., Ali, M., Ragab, A., Michoud, G., … Saikaly, P. E. (2019). Enrichment of Marinobacter sp. and Halophilic Homoacetogens at the Biocathode of Microbial Electrosynthesis System Inoculated With Red Sea Brine Pool. Frontiers in Microbiology, 10. doi:10.3389/fmicb.2019.02563
SponsorsThis work was supported by Competitive Research Grant (URF/1/2985-01-01) from King Abdullah University of Science and Technology to PS. DD acknowledges KAUST support through baseline funding and Red Sea Research Center competitive fund.
The authors would like to thank Dr. Srikanth Pedireddy for conducting SEM and EDX analysis and the crew of R/V Thuwal for their help during brine pool sampling.
PublisherFrontiers Media SA
JournalFrontiers in Microbiology
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Except where otherwise noted, this item's license is described as Copyright © 2019 Alqahtani, Bajracharya, Katuri, Ali, Ragab, Michoud, Daffonchio and Saikaly. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.