Genome-wide gene regulation of biosynthesis and energy generation by a novel transcriptional repressor in Geobacter species

Ueki, Toshiyuki; Lovley, Derek R.

doi:10.1093/nar/gkp1085

Cited by 52 publications

(40 citation statements)

References 60 publications

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“…The reason for this general response might be that the hydrogen-dependent growth transcriptional regulator HgtR is down- regulated. HgtR has been shown to repress genes involved in biosynthesis and energy generation (39). Although HgtR is downregulated under cocultivation conditions, the typical uptake hydrogenase, HybAB (40), of G. sulfurreducens is strongly upregulated (average upregulation of hyb genes, 17.5-fold).…”

Section: Resultsmentioning

confidence: 99%

Resilience, Dynamics, and Interactions within a Model Multispecies Exoelectrogenic-Biofilm Community

Prokhorova

Sturm-Richter

Doetsch

et al. 2017

Appl Environ Microbiol

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Anode-associated multispecies exoelectrogenic biofilms are essential for the function of bioelectrochemical systems (BESs). The individual activities of anodeassociated organisms and physiological responses resulting from coculturing are often hard to assess due to the high microbial diversity in these systems. Therefore, we developed a model multispecies biofilm comprising three exoelectrogenic proteobacteria, Shewanella oneidensis, Geobacter sulfurreducens, and Geobacter metallireducens, with the aim to study in detail the biofilm formation dynamics, the interactions between the organisms, and the overall activity of an exoelectrogenic biofilm as a consequence of the applied anode potential. The experiments revealed that the organisms build a stable biofilm on an electrode surface that is rather resilient to changes in the redox potential of the anode. The community operated at maximum electron transfer rates at electrode potentials that were higher than 0.04 V versus a normal hydrogen electrode. Current densities decreased gradually with lower potentials and reached half-maximal values at Ϫ0.08 V. Transcriptomic results point toward a positive interaction among the individual strains. S. oneidensis and G. sulfurreducens upregulated their central metabolisms as a response to cultivation under mixed-species conditions. G. sulfurreducens was detected in the planktonic phase of the bioelectrochemical reactors in mixed-culture experiments but not when it was grown in the absence of the other two organisms.IMPORTANCE In many cases, multispecies communities can convert organic substrates into electric power more efficiently than axenic cultures, a phenomenon that remains unresolved. In this study, we aimed to elucidate the potential mutual effects of multispecies communities in bioelectrochemical systems to understand how microbes interact in the coculture anodic network and to improve the community's conversion efficiency for organic substrates into electrical energy. The results reveal positive interactions that might lead to accelerated electron transfer in mixedspecies anode communities. The observations made within this model biofilm might be applicable to a variety of nonaxenic systems in the field.KEYWORDS bioelectrochemical systems, Shewanella, Geobacter, exoelectrogenic biofilm, transcriptome analysis S everal microorganisms have the ability to transfer respiratory electrons to an extracellular electron acceptor. Extracellular respiration is highly relevant for a number of biogeochemical cycles, because these electron transport chains were developed for reducing metal oxides as well as for nonmembrane-permeable environmental electron shuttles, such as humic substances (1-4). It is likely that the selective pressure to evolve terminal reductases that catalyze electron transfer to solid electron

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Section: Resultsmentioning

confidence: 99%

Resilience, Dynamics, and Interactions within a Model Multispecies Exoelectrogenic-Biofilm Community

Prokhorova

Sturm-Richter

Doetsch

et al. 2017

Appl Environ Microbiol

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“…1). The likely explanation for this difference is that the expression of citrate synthase in G. sulfurreducens is inhibited in the presence of H 2 , preventing acetate metabolism (4,38). Thus, the availability of H 2 in P. carbinolicus-G. sulfurreducens cocultures would be expected to limit acetate metabolism of G. sulfurreducens, whereas no such inhibition of acetate metabolism is expected in G. metallireducens-G. sulfurreducens cocultures because of the lack of H 2 production during DIET.…”

Section: Resultsmentioning

confidence: 99%

Interspecies Electron Transfer via Hydrogen and Formate Rather than Direct Electrical Connections in Cocultures of Pelobacter carbinolicus and Geobacter sulfurreducens

Rotaru

Shrestha

Liu

et al. 2012

Appl Environ Microbiol

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143

138

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Direct interspecies electron transfer (DIET) is an alternative to interspecies H 2 /formate transfer as a mechanism for microbial species to cooperatively exchange electrons during syntrophic metabolism. To understand what specific properties contribute to DIET, studies were conducted with Pelobacter carbinolicus, a close relative of Geobacter metallireducens, which is capable of DIET. P. carbinolicus grew in coculture with Geobacter sulfurreducens with ethanol as the electron donor and fumarate as the electron acceptor, conditions under which G. sulfurreducens formed direct electrical connections with G. metallireducens. In contrast to the cell aggregation associated with DIET, P. carbinolicus and G. sulfurreducens did not aggregate. Attempts to initiate cocultures with a genetically modified strain of G. sulfurreducens incapable of both H 2 and formate utilization were unsuccessful, whereas cocultures readily grew with mutant strains capable of formate but not H 2 uptake or vice versa. The hydrogenase mutant of G. sulfurreducens compensated, in cocultures, with significantly increased formate dehydrogenase gene expression. In contrast, the transcript abundance of a hydrogenase gene was comparable in cocultures with that for the formate dehydrogenase mutant of G. sulfurreducens or the wild type, suggesting that H 2 was the primary electron carrier in the wild-type cocultures. Cocultures were also initiated with strains of G. sulfurreducens that could not produce pili or OmcS, two essential components for DIET. The finding that P. carbinolicus exchanged electrons with G. sulfurreducens via interspecies transfer of H 2 /formate rather than DIET demonstrates that not all microorganisms that can grow syntrophically are capable of DIET and that closely related microorganisms may use significantly different strategies for interspecies electron exchange.

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“…The fgrM gene from the KN400 strain was amplified by PCR with primers fgrM-DB1 and fgrM-DB2 (supplemental Table S1) and cloned in pET24b (Novagen). FgrM protein was prepared with a histidine tag at the C terminus as described previously (32).…”

Section: Methodsmentioning

confidence: 99%

Identification of Multicomponent Histidine-Aspartate Phosphorelay System Controlling Flagellar and Motility Gene Expression in Geobacter Species

Ueki

Leang

Inoue

et al. 2012

Journal of Biological Chemistry

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Genome-wide gene regulation of biosynthesis and energy generation by a novel transcriptional repressor in Geobacter species

Cited by 52 publications

References 60 publications

Resilience, Dynamics, and Interactions within a Model Multispecies Exoelectrogenic-Biofilm Community

Resilience, Dynamics, and Interactions within a Model Multispecies Exoelectrogenic-Biofilm Community

Interspecies Electron Transfer via Hydrogen and Formate Rather than Direct Electrical Connections in Cocultures of Pelobacter carbinolicus and Geobacter sulfurreducens

Identification of Multicomponent Histidine-Aspartate Phosphorelay System Controlling Flagellar and Motility Gene Expression in Geobacter Species

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