Using Oxidative Electrodes to Enrich Novel Members in the Desulfobulbaceae Family from Intertidal Sediments.

Cheng Li,Clare E Reimers,Yvan Alleau

doi:10.3390/microorganisms9112329

Abstract

Members in the family of Desulfobulbaceae may be influential in various anaerobic microbial communities, including those in anoxic aquatic sediments and water columns, and within wastewater treatment facilities and bioelectrochemical systems (BESs) such as microbial fuel cells (MFCs). However, the diversity and roles of the Desulfobulbaceae in these communities have received little attention, and large portions of this family remain uncultured. Here we expand on findings from an earlier study (Li, Reimers, and Alleau, 2020) to more fully characterize Desulfobulbaceae that became prevalent in biofilms on oxidative electrodes of bioelectrochemical reactors. After incubations, DNA extraction, microbial community analyses, and microscopic examination, we found that a group of uncultured Desulfobulbaceae were greatly enriched on electrode surfaces. These Desulfobulbaceae appeared to form filaments with morphological features ascribed to cable bacteria, but the majority were taxonomically distinct from recognized cable bacteria genera. Thus, the present study provides new information about a group of Desulfobulbaceae that can exhibit filamentous morphologies and respire on the oxidative electrodes. While the phylogeny of cable bacteria is still being defined and updated, further enriching these members can contribute to the overall understanding of cable bacteria and may also lead to identification of successful isolation strategies.

Highlights

IntroductionVarious microorganisms conserve energy by passing electrons over distances greater than their cell-length [1,2]
The present study has demonstrated the possibility of using bioelectrochemical reactors to enrich a group of novel Desulfobulbaceae that were observed to form filaments and respire on the oxidative electrodes
Desulfobulbaceae will help us to learn their role in ecology and elemental cycling and may provide a successful strategy to fully isolate these and other electrogenic taxa that can perform direct extracellular electron transfer (DEET)

Summary

Introduction

Various microorganisms conserve energy by passing electrons over distances greater than their cell-length [1,2]. By tightly coupling electron donors and acceptors, mechanisms of direct extracellular electron transfer (DEET) grant microbial cells competitive advantages in locations where the diffusive transfer of chemical shuttles is limited. DEET mechanisms have been extensively characterized in several model microorganisms and systems, including Geobacter, a genus classified under the Deltaproteobacteria, Shewanella, a genus of Gammaproteobacteria, and the consortia of anaerobic methane-oxidizing archaea and sulfate-reducing bacteria [3–5]. Culture-independent molecular techniques such as catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH), 16S rRNA gene surveys, and metagenome analyses have suggested that there are many diverse microorganisms in a variety of environments that have the functional ability to perform

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Discussion

Conclusion