scholarly journals The Rnf Complex Is an Energy-Coupled Transhydrogenase Essential To Reversibly Link Cellular NADH and Ferredoxin Pools in the AcetogenAcetobacterium woodii

2018 ◽  
Vol 200 (21) ◽  
Author(s):  
Lars Westphal ◽  
Anja Wiechmann ◽  
Jonathan Baker ◽  
Nigel P. Minton ◽  
Volker Müller
Keyword(s):  
Energy Conservation ◽  
Electron Flow ◽  
Low Energy ◽  
Main Function ◽  
Autotrophic Growth ◽  
Acetobacterium Woodii ◽  
Lactate Oxidation ◽  
Energy Substrates ◽  
Content Type ◽  
Respiratory Enzyme

ABSTRACTThe Rnf complex is a respiratory enzyme that catalyzes the oxidation of reduced ferredoxin to the reduction of NAD+, and the negative free energy change of this reaction is used to generate a transmembrane ion gradient. In one class of anaerobic acetogenic bacteria, the Rnf complex is believed to be essential for energy conservation and autotrophic growth. We describe here a methodology for markerless mutagenesis in the model bacterium of this class,Acetobacterium woodii, which enabled us to delete thernfgenes and to test theirin vivorole. Thernfmutant did not grow on H2plus CO2, nor did it produce acetate or ATP from H2plus CO2, and ferredoxin:NAD+oxidoreductase activity and Na+translocation were also completely lost, supporting the hypothesis that the Rnf complex is the only respiratory enzyme in this metabolism. Unexpectedly, the mutant also did not grow on low-energy substrates, such as ethanol or lactate. Oxidation of these substrates is not coupled to the reduction of ferredoxin but only of NAD+, and we speculated that the growth phenotype is caused by a loss of reduced ferredoxin, indispensable for biosynthesis and CO2reduction. The electron-bifurcating hydrogenase ofA. woodiireduces ferredoxin, and indeed, the addition of H2to the cultures restored growth on ethanol and lactate. This is consistent with the hypothesis that endergonic reduction of ferredoxin with NADH is driven by reverse electron transport catalyzed by the Rnf complex, which renders the Rnf complex essential also for growth on low-energy substrates.IMPORTANCEFerredoxin and NAD+are key electron carriers in anaerobic bacteria, but energetically, they are not equivalent, since the redox potential of ferredoxin is lower than that of the NADH/NAD+couple. We describe by mutant studies inAcetobacterium woodiithat the main function of Rnf is to energetically link cellular pools of ferredoxin and NAD+. When ferredoxin is greater than NADH, exergonic electron flow from ferredoxin to NAD+generates a chemiosmotic potential. This is essential for energy conservation during autotrophic growth. When NADH is greater than ferredoxin, Rnf works in reverse. This reaction is essential for growth on low-energy substrates to provide reduced ferredoxin, indispensable for biosynthesis and CO2reduction. Our studies put a new perspective on the cellular function of the membrane-bound ion-translocating Rnf complex widespread in bacteria.

scholarly journals The Rnf Complex of Clostridium ljungdahlii Is a Proton-Translocating Ferredoxin:NAD+ Oxidoreductase Essential for Autotrophic Growth

mBio ◽  
2012 ◽  
Vol 4 (1) ◽  
Author(s):  
Pier-Luc Tremblay ◽  
Tian Zhang ◽  
Shabir A. Dar ◽  
Ching Leang ◽  
Derek R. Lovley
Keyword(s):  
Energy Conservation ◽  
Atp Synthesis ◽  
Proton Motive Force ◽  
Motive Force ◽  
Proton Gradient ◽  
Heterotrophic Growth ◽  
Deficient Mutant ◽  
Autotrophic Growth ◽  
Content Type ◽  
Clostridium Ljungdahlii

ABSTRACTIt has been predicted that the Rnf complex ofClostridium ljungdahliiis a proton-translocating ferredoxin:NAD+oxidoreductase which contributes to ATP synthesis by an H+-translocating ATPase under both autotrophic and heterotrophic growth conditions. The recent development of methods for genetic manipulation ofC. ljungdahliimade it possible to evaluate the possible role of the Rnf complex in energy conservation. Disruption of theC. ljungdahlii rnfoperon inhibited autotrophic growth. ATP synthesis, proton gradient, membrane potential, and proton motive force collapsed in the Rnf-deficient mutant with H2as the electron source and CO2as the electron acceptor. Heterotrophic growth was hindered in the absence of a functional Rnf complex, as ATP synthesis, proton gradient, and proton motive force were significantly reduced with fructose as the electron donor. Growth of the Rnf-deficient mutant was also inhibited when no source of fixed nitrogen was provided. These results demonstrate that the Rnf complex ofC. ljungdahliiis responsible for translocation of protons across the membrane to elicit energy conservation during acetogenesis and is a multifunctional device also implicated in nitrogen fixation.IMPORTANCEMechanisms for energy conservation in the acetogenClostridium ljungdahliiare of interest because of its potential value as a chassis for the production of biocommodities with novel electron donors such as carbon monoxide, syngas, and electrons derived from electrodes. Characterizing the components implicated in the chemiosmotic ATP synthesis during acetogenesis byC. ljungdahliiis a prerequisite for the development of highly productive strains. The Rnf complex has been considered the prime candidate to be the pump responsible for the formation of an ion gradient coupled with ATP synthesis in multiple acetogens. However, experimental evidence for a proton-pumping Rnf complex has been lacking. This study establishes theC. ljungdahliiRnf complex as a proton-translocating ferredoxin:NAD+oxidoreductase and demonstrates thatC. ljungdahliihas the potential of becoming a model organism to study proton translocation, electron transport, and other functions of the Rnf complex in energy conservation or other processes.

scholarly journals Heterotrimeric NADH-Oxidizing Methylenetetrahydrofolate Reductase from the Acetogenic Bacterium Acetobacterium woodii

2015 ◽  
Vol 197 (9) ◽  
pp. 1681-1689 ◽  
Author(s):  
Johannes Bertsch ◽  
Christian Öppinger ◽  
Verena Hess ◽  
Julian D. Langer ◽  
Volker Müller
Keyword(s):  
Energy Conservation ◽  
Methylenetetrahydrofolate Reductase ◽  
Reductase Activity ◽  
Stable Complex ◽  
Acetobacterium Woodii ◽  
Oxidoreductase Activity ◽  
Content Type ◽  
Acetogenic Bacteria ◽  
Acetogenic Bacterium ◽  
Flavin Mononucleotides

ABSTRACTThe methylenetetrahydrofolate reductase (MTHFR) of acetogenic bacteria catalyzes the reduction of methylene-THF, which is highly exergonic with NADH as the reductant. Therefore, the enzyme was suggested to be involved in energy conservation by reducing ferredoxin via electron bifurcation, followed by Na+translocation by the Rnf complex. The enzyme was purified fromAcetobacterium woodiiand shown to have an unprecedented subunit composition containing the three subunits RnfC2, MetF, and MetV. The stable complex contained 2 flavin mononucleotides (FMN), 23.5 ± 1.2 Fe and 24.5 ± 1.5 S, which fits well to the predicted six [4Fe4S] clusters in MetV and RnfC2. The enzyme catalyzed NADH:methylviologen and NADH:ferricyanide oxidoreductase activity but also methylene-tetrahydrofolate (THF) reduction with NADH as the reductant. The NADH:methylene-THF reductase activity was high (248 U/mg) and not stimulated by ferredoxin. Furthermore, reduction of ferredoxin, alone or in the presence of methylene-THF and NADH, was never observed. MetF or MetVF was not able to catalyze the methylene-THF-dependent oxidation of NADH, but MetVF could reduce methylene-THF using methyl viologen as the electron donor. The purified MTHFR complex did not catalyze the reverse reaction, the endergonic oxidation of methyl-THF with NAD+as the acceptor, and this reaction could not be driven by reduced ferredoxin. However, addition of protein fractions made the oxidation of methyl-THF to methylene-THF coupled to NAD+reduction possible. Our data demonstrate that the MTHFR ofA. woodiicatalyzes methylene-THF reduction according to the following reaction: NADH + methylene-THF → methyl-THF + NAD+. The differences in the subunit compositions of MTHFRs of bacteria are discussed in the light of their different functions.IMPORTANCEEnergy conservation in the acetogenic bacteriumAcetobacterium woodiiinvolves ferredoxin reduction followed by a chemiosmotic mechanism involving Na+-translocating ferredoxin oxidation and a Na+-dependent F1FoATP synthase. All redox enzymes of the pathway have been characterized except the methylenetetrahydrofolate reductase (MTHFR). Here we report the purification of the MTHFR ofA. woodii, which has an unprecedented heterotrimeric structure. The enzyme reduces methylene-THF with NADH. Ferredoxin did not stimulate the reaction; neither was it oxidized or reduced with NADH. Since the last enzyme with a potential role in energy metabolism ofA. woodiihas now been characterized, we can propose a quantitative bioenergetic scheme for acetogenesis from H2plus CO2in the model acetogenA. woodii.

scholarly journals Lactose-Inducible System for Metabolic Engineering of Clostridium ljungdahlii

2014 ◽  
Vol 80 (8) ◽  
pp. 2410-2416 ◽  
Author(s):  
Areen Banerjee ◽  
Ching Leang ◽  
Toshiyuki Ueki ◽  
Kelly P. Nevin ◽  
Derek R. Lovley
Keyword(s):  
Ethanol Production ◽  
Genetic Manipulation ◽  
Electron Flow ◽  
Model Organism ◽  
Inducible Expression ◽  
Carbon Flow ◽  
Wild Type ◽  
Content Type ◽  
Microbial Electrosynthesis ◽  
Clostridium Ljungdahlii

ABSTRACTThe development of tools for genetic manipulation ofClostridium ljungdahliihas increased its attractiveness as a chassis for autotrophic production of organic commodities and biofuels from syngas and microbial electrosynthesis and established it as a model organism for the study of the basic physiology of acetogenesis. In an attempt to expand the genetic toolbox forC. ljungdahlii, the possibility of adapting a lactose-inducible system for gene expression, previously reported forClostridium perfringens, was investigated. The plasmid pAH2, originally developed forC. perfringenswith agusAreporter gene, functioned as an effective lactose-inducible system inC. ljungdahlii. Lactose induction ofC. ljungdahliicontaining pB1, in which the gene for the aldehyde/alcohol dehydrogenase AdhE1 was downstream of the lactose-inducible promoter, increased expression ofadhE130-fold over the wild-type level, increasing ethanol production 1.5-fold, with a corresponding decrease in acetate production. Lactose-inducible expression ofadhE1in a strain in whichadhE1and theadhE1homologadhE2had been deleted from the chromosome restored ethanol production to levels comparable to those in the wild-type strain. Inducing expression ofadhE2similarly failed to restore ethanol production, suggesting thatadhE1is the homolog responsible for ethanol production. Lactose-inducible expression of the four heterologous genes necessary to convert acetyl coenzyme A (acetyl-CoA) to acetone diverted ca. 60% of carbon flow to acetone production during growth on fructose, and 25% of carbon flow went to acetone when carbon monoxide was the electron donor. These studies demonstrate that the lactose-inducible system described here will be useful for redirecting carbon and electron flow for the biosynthesis of products more valuable than acetate. Furthermore, this tool should aid in optimizing microbial electrosynthesis and for basic studies on the physiology of acetogenesis.

Role of BIM and energy simulation tools in designing zero-net energy homes

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Shahryar Habibi
Keyword(s):  
Energy Efficiency ◽  
Built Environment ◽  
Design Process ◽  
Simulation Software ◽  
Energy Simulation ◽  
Low Energy ◽  
Net Energy ◽  
Content Type ◽  
Zero Net Energy

Purpose The purpose of this study is to design a zero-energy home, which is known to be capable of balancing its own energy production and consumption close to zero. Development of low-energy homes and zero-net energy houses (ZEHs) is vital to move toward energy efficiency and sustainability in the built environment. To achieve zero or low energy targets in homes, it is essential to use the design process that minimizes the need for active mechanical systems. Design/methodology/approach The methodology discussed in this paper consists of an interfacing building information modeling (BIM) tool and a simulation software to determine the potential influence of phase change materials on designing zero-net energy homes. Findings BIM plays a key role in advancing methods for architects and designers to communicate through a common software platform, analyze energy performance through all stages of the design and construction process and make decisions for improving energy efficiency in the built environment. Originality/value This paper reviews the literature relevant to the role of BIM in helping energy simulation for the performance of residential homes to more advanced levels and in modeling the integrated design process of ZEHs.

scholarly journals SfnR2 Regulates Dimethyl Sulfide-Related Utilization inPseudomonas aeruginosaPAO1

2018 ◽  
Vol 201 (4) ◽  
Author(s):  
Benjamin R. Lundgren ◽  
Zaara Sarwar ◽  
Kyle S. Feldman ◽  
Joseph M. Shoytush ◽  
Christopher T. Nomura
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Target Genes ◽  
Dimethyl Sulfide ◽  
Sulfur Compound ◽  
Main Function ◽  
Gene Encoding ◽  
Content Type ◽  
First Results ◽  
Terrestrial Environments ◽  
Initial Activation

ABSTRACTDimethyl sulfide (DMS) is a volatile sulfur compound produced mainly from the degradation of dimethylsulfoniopropionate (DMSP) in marine environments. DMS undergoes oxidation to form dimethyl sulfoxide (DMSO), dimethyl sulfone (DMSO2), and methanesulfonate (MSA), all of which occur in terrestrial environments and are accessible for consumption by various microorganisms. The purpose of the present study was to determine how the enhancer-binding proteins SfnR1 and SfnR2 contribute to the utilization of DMS and its derivatives inPseudomonas aeruginosaPAO1. First, results from cell growth experiments showed that deletion of eithersfnR2orsfnG, a gene encoding a DMSO2-monooxygenase, significantly inhibits the ability ofP. aeruginosaPAO1 to use DMSP, DMS, DMSO, and DMSO2as sulfur sources. Deletion of thesfnR1ormsuEDCgenes, which encode a MSA desulfurization pathway, did not abolish the growth ofP. aeruginosaPAO1 on any sulfur compound tested. Second, data collected from β-galactosidase assays revealed that themsuEDC-sfnR1operon and thesfnGgene are induced in response to sulfur limitation or nonpreferred sulfur sources, such as DMSP, DMS, and DMSO, etc. Importantly, SfnR2 (and not SfnR1) is essential for this induction. Expression ofsfnR2is induced under sulfur limitation but independently of SfnR1 or SfnR2. Finally, the results of this study suggest that the main function of SfnR2 is to direct the initial activation of themsuEDC-sfnR1operon in response to sulfur limitation or nonpreferred sulfur sources. Once expressed, SfnR1 contributes to the expression ofmsuEDC-sfnR1,sfnG, and other target genes involved in DMS-related metabolism inP. aeruginosaPAO1.IMPORTANCEDimethyl sulfide (DMS) is an important environmental source of sulfur, carbon, and/or energy for microorganisms. For various bacteria, includingPseudomonas,Xanthomonas, andAzotobacter, DMS utilization is thought to be controlled by the transcriptional regulator SfnR. Adding more complexity, some bacteria, such asAcinetobacter baumannii,Enterobacter cloacae, andPseudomonas aeruginosa, possess two, nonidentical SfnR proteins. In this study, we demonstrate that SfnR2 and not SfnR1 is the principal regulator of DMS metabolism inP. aeruginosaPAO1. Results suggest that SfnR1 has a supportive but nonessential role in the positive regulation of genes required for DMS utilization. This study not only enhances our understanding of SfnR regulation but, importantly, also provides a framework for addressing gene regulation through dual SfnR proteins in other bacteria.

scholarly journals The Staphylococcus aureus KdpDE Two-Component System Couples Extracellular K+Sensing and Agr Signaling to Infection Programming

2011 ◽  
Vol 79 (6) ◽  
pp. 2154-2167 ◽  
Author(s):  
Ting Xue ◽  
Yibo You ◽  
De Hong ◽  
Haipeng Sun ◽  
Baolin Sun
Keyword(s):  
Staphylococcus Aureus ◽  
Uptake System ◽  
Main Function ◽  
Two Component System ◽  
Component System ◽  
Content Type ◽  
Two Component ◽  
Virulence Regulator ◽  
External K

ABSTRACTThe Kdp system is widely distributed among bacteria. InEscherichia coli, the Kdp-ATPase is a high-affinity K+uptake system and its expression is activated by the KdpDE two-component system in response to K+limitation or salt stress. However, information about the role of this system in many bacteria still remains obscure. Here we demonstrate that KdpFABC inStaphylococcus aureusis not a major K+transporter and that the main function of KdpDE is not associated with K+transport but that instead it regulates transcription for a series of virulence factors through sensing external K+concentrations, indicating that this bacterium might modulate its infectious status through sensing specific external K+stimuli in different environments. Our results further reveal thatS. aureusKdpDE is upregulated by the Agr/RNAIII system, which suggests that KdpDE may be an important virulence regulator coordinating the external K+sensing and Agr signaling during pathogenesis in this bacterium.

Conceptualisation, development and validation of green marketing orientation (GMO) of SMEs in India

2014 ◽  
Vol 5 (2) ◽  
pp. 312-337 ◽  
Author(s):  
Hardeep Chahal ◽  
Ramesh Dangwal ◽  
Swati Raina
Keyword(s):  
Supply Chain ◽  
Supply Chain Management ◽  
Energy Conservation ◽  
Green Marketing ◽  
Green Supply Chain Management ◽  
Green Supply Chain ◽  
Chain Management ◽  
Content Type ◽  
Marketing Orientation ◽  
Strategic Policy

Purpose – The purpose of the study is twofold. First, to examine the domain of green marketing construct in the context of small and medium enterprises (SMEs) operating in emerging economies (i.e. India) across electrical industries and, second, to assess its impact on the SMEs performance. Design/methodology/approach – All the owners of electrical industries (SMEs) operating in Jammu District, that is, 152, were contacted using census method. Findings – The study identifies and confirms five factors, namely, greening the process, green supply chain management, green strategic policy initiative, proactive energy conservation and green innovation of green marketing as important dimensions of green marketing orientation (GMO) scale. All the dimensions of the GMO scale have positive and significant impacts on performance of the firms. In addition, there exists stronger impact of green marketing dimensions on the customer business to business (B2B) satisfaction and employee retention. Research limitations/implications – The research has certain unavoidable limitations. First, the study is based on only one sector, that is, electrical industries operating in developing industrial region of India and hence future research is suggested to comprehend green marketing in other green-savvy manufacturing sectors like pharmaceutical sector and service sector like hotels and hospitals. Further, the study has focussed on the development of GMO scale and future studies need to extend research to include variables like green satisfaction, green trust and green loyalty to understand their mediating role in green marketing and performance relationship. Furthermore, the moderating role of variables such as nature and age of the SMEs can also be studied in future research. Practical implications – GMO allows managers to understand how their firms facilitate green environment and they affect the business outcomes. Furthermore, GMO takes into consideration all important aspects (greening the process, green supply chain management, green strategic policy initiatives, proactive energy conservation and green promotion) which provide better explanatory power and identification of priority areas for managerial attention. GMO can be used by managers to determine which strategies and practices will have the most positive influence on employees’ outcome. Originality/value – This paper can help managers in identifying the perspectives of GMO in electrical sector for the developing countries. Unlike the three dimensions confirmed by studies, this study established five dimensions of green marketing, namely, greening the process green supply chain management, green strategic policy initiatives, proactive energy conservation and green promotion.

scholarly journals Brachiopod-dominated communities and depositional environment of the Guanshan Konservat-Lagerstätte, eastern Yunnan, China

2020 ◽  
Vol 178 (1) ◽  
pp. jgs2020-043 ◽  
Author(s):  
Feiyang Chen ◽  
Glenn A. Brock ◽  
Zhiliang Zhang ◽  
Brittany Laing ◽  
Xinyi Ren ◽  
...  
Keyword(s):  
Depositional Environment ◽  
Sedimentary Environment ◽  
Low Energy ◽  
Cambrian Explosion ◽  
Early Cambrian ◽  
Tissue Preservation ◽  
Content Type ◽  
Guanshan Biota ◽  
Supplementary Material ◽  
Later Phase

The Guanshan Biota is an unusual early Cambrian Konservat-Lagerstätte from China and is distinguished from all other exceptionally preserved Cambrian biotas by the dominance of brachiopods and a relatively shallow depositional environment. However, the faunal composition, overturn and sedimentology associated with the Guanshan Biota are poorly understood. This study, based on collections through the best-exposed succession of the basal Wulongqing Formation at the Shijiangjun section, Wuding County, eastern Yunnan, China recovered six major animal groups with soft tissue preservation; brachiopods vastly outnumbered all other groups. Brachiopods quickly replace arthropods as the dominant fauna following a transgression at the base of the Wulongqing Formation. A transition from a botsfordiid-, eoobolid- and acrotretid- to an acrotheloid-dominated brachiopod assemblage occurs up-section. Four episodically repeated lithofacies reveal a relatively low-energy, offshore to lower shoreface sedimentary environment at the Shijiangjun section, which is very different from the Wulongqing Formation in the Malong and Kunming areas. Multiple event flows and rapid obrution are responsible for faunal overturn and fluctuation through the section. A detailed lithofacies and palaeontological investigation of this section provides a better understanding of the processes and drivers of faunal overturn during the later phase of the Cambrian Explosion.Supplementary material: Composition and comparison of the Malong Fauna and the Guanshan Biota is are available at: https://doi.org/10.6084/m9.figshare.c.5080799

Workplace energy conservation at Michigan State University

2018 ◽  
Vol 19 (1) ◽  
pp. 114-129 ◽  
Author(s):  
Summer Allen ◽  
Sandra T. Marquart-Pyatt
Keyword(s):  
Energy Conservation ◽  
Energy Use ◽  
Ordinary Least Squares ◽  
Policy Support ◽  
Abc Model ◽  
Least Squares Regression ◽  
Content Type ◽  
Positive Attitudes ◽  
Tpb Model ◽  
Employee Behaviors

Purpose This research contributes to the literature on workplace energy conservation by examining the predictors of individual employee behaviors and policy support in a university. The purpose of this research is to better understand what factors influence energy conservation behaviors in this setting to inform programs and interventions. Design/methodology/approach This project gathered survey data from employee-occupants of three campus buildings. Ordinary least squares regression analyses were used to investigate the theory of planned behavior (TPB) and attitudes-behavior-constraints (ABC) models examining what drives energy behaviors. Findings This study finds a large proportion of respondents would support energy use reduction policies, more technology-based interventions and increased use of renewable sources. Respondents report positive attitudes toward individual energy conservation behavior but mild agreement with the influence of social norms. Self-efficacy reports also are positive. Although the TPB model is not fully supported in this group, the ABC model appears to perform well. Originality/value In addition to adding to the relatively limited data on employee energy-saving behaviors in the university workplace, this study provides initial evidence that the ABC model is pertinent to this behavioral context. It also provides specific, usable data about policies and actions that campus community members might deem feasible and acceptable to relevant university offices.

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