Energetic and Molecular Constraints on the Mechanism of Environmental Fe(III) Reduction by Geobacter

Levar, Caleb E.; Rollefson, Janet B.; Bond, Daniel R.

doi:10.1007/978-3-642-32867-1_2

Cited by 18 publications

(28 citation statements)

References 116 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The Gram-negative obligate anaerobic δ-proteobacterium G. sulfurreducens is used as a model organism for investigating electroactive microorganisms ( Levar et al, 2012 ). Since its genome was sequenced it is easier to analyze the detailed molecular mechanism of EET and to construct molecular models.…”

Section: Varieties Of Microbial Electron Transport Chainsmentioning

confidence: 99%

“…In its genome more than 110 genes coding for putative c-type cytochromes have been identified, which likely play an important role in the electron transport pathway of this bacterium ( Methe et al, 2003 ). It is assumed that several multiheme c-type cytochromes enable the transport of redox equivalents between the cellular menaquinone (MQ) pool and the extracellular insoluble metals to create a proton gradient for energy conservation ( Levar et al, 2012 ). The interaction between the cytochrome complexes in the electron transport chain is based on the redox potential of the different multiheme molecules of the cytochromes, whereby each heme has its own specific redox potential.…”

Section: Varieties Of Microbial Electron Transport Chainsmentioning

confidence: 99%

See 1 more Smart Citation

Microbial electron transport and energy conservation â€“ the foundation for optimizing bioelectrochemical systems

2015

View full text Add to dashboard Cite

Microbial electrochemical techniques describe a variety of emerging technologies that use electrode–bacteria interactions for biotechnology applications including the production of electricity, waste and wastewater treatment, bioremediation and the production of valuable products. Central in each application is the ability of the microbial catalyst to interact with external electron acceptors and/or donors and its metabolic properties that enable the combination of electron transport and carbon metabolism. And here also lies the key challenge. A wide range of microbes has been discovered to be able to exchange electrons with solid surfaces or mediators but only a few have been studied in depth. Especially electron transfer mechanisms from cathodes towards the microbial organism are poorly understood but are essential for many applications such as microbial electrosynthesis. We analyze the different electron transport chains that nature offers for organisms such as metal respiring bacteria and acetogens, but also standard biotechnological organisms currently used in bio-production. Special focus lies on the essential connection of redox and energy metabolism, which is often ignored when studying bioelectrochemical systems. The possibility of extracellular electron exchange at different points in each organism is discussed regarding required redox potentials and effect on cellular redox and energy levels. Key compounds such as electron carriers (e.g., cytochromes, ferredoxin, quinones, flavins) are identified and analyzed regarding their possible role in electrode–microbe interactions. This work summarizes our current knowledge on electron transport processes and uses a theoretical approach to predict the impact of different modes of transfer on the energy metabolism. As such it adds an important piece of fundamental understanding of microbial electron transport possibilities to the research community and will help to optimize and advance bioelectrochemical techniques.

show abstract

Section: Varieties Of Microbial Electron Transport Chainsmentioning

confidence: 99%

Section: Varieties Of Microbial Electron Transport Chainsmentioning

confidence: 99%

Microbial electron transport and energy conservation â€“ the foundation for optimizing bioelectrochemical systems

2015

View full text Add to dashboard Cite

show abstract

“…Use of environmental metal oxides as terminal electron acceptors by Geobacter requires cell-metal contact to facilitate electron transfer, and while attachment to surfaces is typically regulated by cdiG signaling, our results demonstrate that a separate mechanism has emerged for metal particle attachment. In retrospect, permanent biofilm-like attachment as driven by cdiG signaling would be a poor choice for interacting with environmental metal oxides, as Fe(III) oxides are usually nanophase (<100 nm), and a single metal particle cannot provide enough energy to support cell division (Levar et al, 2013;Zacharoff et al, 2017). Thus, based on energetics and size, metal oxides present a conundrum for metal-reducing bacteria: a surface that requires transient, rather than permanent, contact.…”

Section: Discussionmentioning

confidence: 99%

cGAMP signaling controls a transient surface-associated lifestyle

Zf¹,

Chen

Ta³

et al. 2018

Preprint

View full text Add to dashboard Cite

SUMMARYA newfound signaling pathway employs a GGDEF enzyme with unique activity compared to the majority of homologs associated with bacterial cyclic di-GMP signaling. This system provides a rare opportunity to study how signaling proteins natively gain distinct function. Using genetic knockouts, riboswitch reporters, and RNA-Seq, we show that GacA, the Hypr GGDEF in Geobacter sulfurreducens, specifically regulates cyclic GMP-AMP (3′,3′-cGAMP) levels in vivo to stimulate gene expression associated with metal reduction separate from electricity production. To reconcile these in vivo findings with prior in vitro results that showed GacA was promiscuous, we developed a full kinetic model combining experimental data and mathematical modeling to reveal mechanisms that contribute to in vivo specificity. A 1.4 Å-resolution crystal structure of the Geobacter Hypr GGDEF domain was determined to understand the molecular basis for those mechanisms, including key cross-dimer interactions. Together these results demonstrate that specific signaling can result from a promiscuous enzyme.3

show abstract

“…178 Since its genome was sequenced it is easier to analyse the detailed molecular mechanism of EET and to construct molecular models. In its genome, more than 110 genes coding for putative ctype cytochromes have been identified, which likely play an important role in the electron transport pathway of this bacterium.…”

Section: G Sulfurreducens: Branched Omcs Systemmentioning

confidence: 99%

“…179 It is assumed that several multiheme c-type cytochromes enable the transport of redox equivalents between the cellular menaquinone pool and the extracellular insoluble metals to create a proton gradient for energy conservation. 178 The interaction between the cytochrome complexes in the electron transport chain is based on the redox potential of the different multiheme molecules of the cytochromes, whereby each heme has its own specific redox potential. In this way, wide windows of potential ranges are created that overlap with each other and allow a bioenergetic transfer of electrons.…”

Section: G Sulfurreducens: Branched Omcs Systemmentioning

confidence: 99%

Understanding extracellular electron transport of industrial microorganisms and optimization for production application

Kracke¹

View full text Add to dashboard Cite

Microbial electrosynthesis (MES) and electro-fermentation are novel approaches to increase microbial production by stimulating the metabolism of the cells electrically. The technique is still in its infancy and while already hyped as promising method to convert CO 2 or cheap carbon sources and electrical energy into valuable chemicals and fuels, little is known about its true potential. This project uses a combination of in silico and in vivo approaches to gather novel information about the benefits and limitations of microbial electrosynthesis as well as its fundamental mechanisms.Understanding microbial electron transport mechanisms is the key to optimization of any bioelectrochemical technology. Therefore, this work analyses the different electron transport chains that nature offers for organisms such as metal respiring bacteria and acetogens, but also standard biotechnological organisms currently used in bioproduction.Special focus lies on the essential connection of redox and energy metabolism, which is often ignored when studying bioelectrochemical systems. The possibility of extracellular electron exchange at different points in each organism is discussed regarding required redox potentials and effect on cellular redox and energy levels. Key compounds such as electron carriers (e.g. cytochromes, ferredoxins, quinones, flavins) are identified and analysed regarding their possible role in electrode-microbe-interactions.Based on these findings a stoichiometric network analysis is performed analysing the effect of electrical stimulation on the microbial metabolism theoretically. Escherichia coli is used as model organism for production with the aim to identify target processes for MES.For the first time, 20 different valuable products were screened for their potential to show increased yields during anaerobic electrically enhanced fermentation. Surprisingly it was found that an increase in product formation by electrical enhancement is not necessarily dependent on the degree of reduction of the product but rather the metabolic pathway it is derived from. Contrary to the usual assumption a reduced product would always require electron supply by a cathode this study shows that a complex metabolic analysis is needed to identify the overall redox state of each process. A variety of beneficial processes is presented with product yield increases of maximal +36% in reductive and +84% in oxidative fermentations and final theoretical product yields up to 100%. This includes compounds that are already produced at industrial scale such as succinic acid, ii lysine and diaminopentane as well as potential novel bio-commodities such as isoprene, para-hydroxybenzoic acid and para-aminobenzoic acid. Furthermore, it is shown that the way of electron transport has major impact on achievable biomass and product yields. The coupling of electron transport to energy conservation could be identified as crucial for most processes.The in vivo approach of this project introduces the development of a standardised reactor platfor...

show abstract

Energetic and Molecular Constraints on the Mechanism of Environmental Fe(III) Reduction by Geobacter

Cited by 18 publications

References 116 publications

Microbial electron transport and energy conservation â€“ the foundation for optimizing bioelectrochemical systems

Microbial electron transport and energy conservation â€“ the foundation for optimizing bioelectrochemical systems

cGAMP signaling controls a transient surface-associated lifestyle

Understanding extracellular electron transport of industrial microorganisms and optimization for production application

Contact Info

Product

Resources

About