scholarly journals Species Widely Distributed in Halophilic Archaea Exhibit Opsin-Mediated Inhibition of Bacterioruberin Biosynthesis

2018 ◽  
Vol 201 (2) ◽  
Author(s):  
Ronald F. Peck ◽  
Serena M. Graham ◽  
Abby M. Gregory
Keyword(s):  
Regulatory Mechanism ◽  
Halophilic Archaea ◽  
Halobacterium Salinarum ◽  
Efficient Production ◽  
Carotenoid Pigment ◽  
Prosthetic Group ◽  
Content Type ◽  
Genes Encoding ◽  
The Common ◽  
Insight Into

ABSTRACT Halophilic Archaea are a distinctive pink color due to a carotenoid pigment called bacterioruberin. To sense or utilize light, many halophilic Archaea also produce rhodopsins, complexes of opsin proteins with a retinal prosthetic group. Both bacterioruberin and retinal are synthesized from isoprenoid precursors, with lycopene as the last shared intermediate. We previously described a regulatory mechanism by which Halobacterium salinarum bacterioopsin and Haloarcula vallismortis cruxopsin inhibit bacterioruberin synthesis catalyzed by lycopene elongase. In this work, we found that opsins in all three major Halobacteria clades inhibit bacterioruberin synthesis, suggesting that this regulatory mechanism existed in the common Halobacteria ancestor. Halophilic Archaea, which are generally heterotrophic and aerobic, likely evolved from an autotrophic, anaerobic methanogenic ancestor by acquiring many genes from Bacteria via lateral gene transfer. These bacterial “imports” include genes encoding opsins and lycopene elongases. To determine if opsins from Bacteria inhibit bacterioruberin synthesis, we tested bacterial opsins and found that an opsin from Curtobacterium, in the Actinobacteria phylum, inhibits bacterioruberin synthesis catalyzed by its own lycopene elongase, as well as that catalyzed by several archaeal enzymes. We also determined that the lycopene elongase from Halococcus salifodinae, a species from a family of Halobacteria lacking opsin homologs, retained the capacity to be inhibited by opsins. Together, our results indicate that opsin-mediated inhibition of bacterioruberin biosynthesis is a widely distributed mechanism found in both Archaea and Bacteria, possibly predating the divergence of the two domains. Further analysis may provide insight into the acquisition and evolution of the genes and their host species. IMPORTANCE All organisms use a variety of mechanisms to allocate limited resources to match their needs in their current environment. Here, we explore how halophilic microbes use a novel mechanism to allow efficient production of rhodopsin, a complex of an opsin protein and a retinal prosthetic group. We previously demonstrated that Halobacterium salinarum bacterioopsin directs available resources toward retinal by inhibiting synthesis of bacterioruberin, a molecule that shares precursors with retinal. In this work, we show that this mechanism can be carried out by proteins from halophilic Archaea that are not closely related to H. salinarum and those in at least one species of Bacteria. Therefore, opsin-mediated inhibition of bacterioruberin synthesis may be a highly conserved, ancient regulatory mechanism.

scholarly journals Opsin-Mediated Inhibition of Bacterioruberin Synthesis in Halophilic Archaea

2017 ◽  
Vol 199 (21) ◽  
Author(s):  
Ronald F. Peck ◽  
Alexandru M. Pleşa ◽  
Serena M. Graham ◽  
David R. Angelini ◽  
Emily L. Shaw
Keyword(s):  
Organic Molecules ◽  
Regulatory Mechanism ◽  
Colorimetric Assay ◽  
Halophilic Archaea ◽  
Halobacterium Salinarum ◽  
Haloferax Volcanii ◽  
Content Type ◽  
Colony Color ◽  
Ion Pumping ◽  
Limited Oxygen

ABSTRACT Halophilic archaea often inhabit environments with limited oxygen, and many produce ion-pumping rhodopsin complexes that allow them to maintain electrochemical gradients when aerobic respiration is inhibited. Rhodopsins require a protein, an opsin, and an organic cofactor, retinal. We previously demonstrated that in Halobacterium salinarum, bacterioopsin (BO), when not bound by retinal, inhibits the production of bacterioruberin, a biochemical pathway that shares intermediates with retinal biosynthesis. In this work, we used heterologous expression in a related halophilic archaeon, Haloferax volcanii, to demonstrate that BO is sufficient to inhibit bacterioruberin synthesis catalyzed by the H. salinarum lycopene elongase (Lye) enzyme. This inhibition was observed both in liquid culture and in a novel colorimetric assay to quantify bacterioruberin abundance based on the colony color. Addition of retinal to convert BO to the bacteriorhodopsin complex resulted in a partial rescue of bacterioruberin production. To explore if this regulatory mechanism occurs in other organisms, we expressed a Lye homolog and an opsin from Haloarcula vallismortis in H. volcanii. H. vallismortis cruxopsin-3 expression inhibited bacterioruberin synthesis catalyzed by H. vallismortis Lye but had no effect when bacterioruberin synthesis was catalyzed by H. salinarum or H. volcanii Lye. Conversely, H. salinarum BO did not inhibit H. vallismortis Lye activity. Together, our data suggest that opsin-mediated inhibition of Lye is potentially widespread and represents an elegant regulatory mechanism that allows organisms to efficiently utilize ion-pumping rhodopsins obtained through lateral gene transfer. IMPORTANCE Many enzymes are complexes of proteins and nonprotein organic molecules called cofactors. To ensure efficient formation of functional complexes, organisms must regulate the production of proteins and cofactors. To study this regulation, we used bacteriorhodopsin from the archaeon Halobacterium salinarum. Bacteriorhodopsin consists of the bacterioopsin protein and a retinal cofactor. In this article, we further characterize a novel regulatory mechanism in which bacterioopsin promotes retinal production by inhibiting a reaction that consumes lycopene, a retinal precursor. By expressing H. salinarum genes in a different organism, Haloferax volcanii, we demonstrated that bacterioopsin alone is sufficient for this inhibition. We also found that an opsin from Haloarcula vallismortis has inhibitory activity, suggesting that this regulatory mechanism might be found in other organisms.

scholarly journals Versatility in Corrinoid Salvaging and Remodeling Pathways Supports Corrinoid-Dependent Metabolism in Dehalococcoides mccartyi

2012 ◽  
Vol 78 (21) ◽  
pp. 7745-7752 ◽  
Author(s):  
Shan Yi ◽  
Erica C. Seth ◽  
Yu-Jie Men ◽  
Sally P. Stabler ◽  
Robert H. Allen ◽  
...  
Keyword(s):  
De Novo ◽  
Chlorinated Solvents ◽  
Axial Ligand ◽  
Content Type ◽  
Dehalococcoides Mccartyi ◽  
Axial Ligands ◽  
The Common ◽  
Enzyme Cofactors ◽  
Lower Ligand ◽  
Insight Into

ABSTRACTCorrinoids are cobalt-containing molecules that function as enzyme cofactors in a wide variety of organisms but are produced solely by a subset of prokaryotes. Specific corrinoids are identified by the structure of their axial ligands. The lower axial ligand of a corrinoid can be a benzimidazole, purine, or phenolic compound. Though it is known that many organisms obtain corrinoids from the environment, the variety of corrinoids that can serve as cofactors for any one organism is largely unstudied. Here, we examine the range of corrinoids that function as cofactors for corrinoid-dependent metabolism inDehalococcoides mccartyistrain 195.Dehalococcoidesbacteria play an important role in the bioremediation of chlorinated solvents in the environment because of their unique ability to convert the common groundwater contaminants perchloroethene and trichloroethene to the innocuous end product ethene. All isolatedD. mccartyistrains require exogenous corrinoids such as vitamin B12for growth. However, like many other corrinoid-dependent bacteria, none of the well-characterizedD. mccartyistrains has been shown to be capable of synthesizing corrinoidsde novo. In this study, we investigate the ability ofD. mccartyistrain 195 to use specific corrinoids, as well as its ability to modify imported corrinoids to a functional form. We show that strain 195 can use only specific corrinoids containing benzimidazole lower ligands but is capable of remodeling other corrinoids by lower ligand replacement when provided a functional benzimidazole base. This study of corrinoid utilization and modification byD. mccartyiprovides insight into the array of strategies that microorganisms employ in acquiring essential nutrients from the environment.

scholarly journals An Extracytoplasmic Function Sigma Factor Controls Cellulose Utilization by Regulating the Expression of an Outer Membrane Protein inCytophaga hutchinsonii

2018 ◽  
Vol 85 (5) ◽  
Author(s):  
Xia Wang ◽  
Weixin Zhang ◽  
Hong Zhou ◽  
Guanjun Chen ◽  
Weifeng Liu
Keyword(s):  
Membrane Protein ◽  
Outer Membrane ◽  
Outer Membrane Protein ◽  
Regulatory Mechanism ◽  
Outer Membrane Proteins ◽  
Cellulolytic Bacterium ◽  
Content Type ◽  
Cytophaga Hutchinsonii ◽  
Σ Factor ◽  
The Common

ABSTRACTThe common soil cellulolytic bacterium known asCytophaga hutchinsoniimakes use of a unique but poorly understood strategy in order to utilize cellulose. While several genes have been identified as being an active part of the utilization of cellulose, the mechanism(s) by whichC. hutchinsoniiboth (i) senses its environment and (ii) regulates the expression of those genes are not as yet known. In this study, we identified and characterized the geneCHU_3097encoding an extracytoplasmic function (ECF) σ factor (σcel1), the disruption of which compromisedC. hutchinsoniicellulose assimilation to a large degree. The σcel1and its putative partner anti-σcel1, encoded by theCHU_3096gene found immediately downstream fromCHU_3097, copurifiedin vitro. The σcel1was discovered to be associated with inner membrane when cells were cultured on glucose and yet was partially released from the membrane in response to cellulose. This release was found to occur on glucose when the anti-σcel1was absent. Transcriptome analyses found a σcel1-regulated, cellulose-responsive gene regulon, within which an outer membrane protein encoding the geneCHU_1276, essential for cellulose utilization, was discovered to be significantly downregulated byCHU_3097disruption. The expression of CHU_1276 almost fully restored cellulose utilization to theCHU_3097mutant, demonstrating that CHU_1276 represents a critical regulatory target of σcel1. In this way, our study provided insights into the role of an ECF σ factor in coordinating the cellulolytic response ofC. hutchinsonii.IMPORTANCEThe common cellulolytic bacteriumCytophaga hutchinsoniiuses a unique but poorly understood strategy in order to make use of cellulose. Throughout the process of cellulosic biomass breakdown, outer membrane proteins are thought to play key roles; this is evidenced by CHU_1276, which is required for the utilization of cellulose. However, the regulatory mechanism of its expression is not yet known. We found and characterized an extracytoplasmic function σ factor that is involved in coordinating the cellulolytic response ofC. hutchinsoniiby directly regulating the expression ofCHU_1276. This study makes a contribution to our understanding of the regulatory mechanism used byC. hutchinsoniiin order to adjust its genetic programs and so deal with novel environmental cues.

scholarly journals Efficient Production of 2,5-Diketo-d-Gluconate via Heterologous Expression of 2-Ketogluconate Dehydrogenase in Gluconobacter japonicus

2015 ◽  
Vol 81 (10) ◽  
pp. 3552-3560 ◽  
Author(s):  
Naoya Kataoka ◽  
Minenosuke Matsutani ◽  
Toshiharu Yakushi ◽  
Kazunobu Matsushita
Keyword(s):  
Mutant Strain ◽  
Gluconobacter Oxydans ◽  
Efficient Production ◽  
Broad Host Range ◽  
Putative Promoter Region ◽  
Content Type ◽  
Biotransformation Process ◽  
Genes Encoding ◽  
Membrane Bound ◽  
Almost All

ABSTRACT2,5-Diketo-d-gluconate (2,5DKG) is a compound that can be the intermediate ford-tartrate and also vitamin C production. AlthoughGluconobacter oxydansNBRC3293 produces 2,5DKG fromd-glucose viad-gluconate and 2-keto-d-gluconate (2KG), with accumulation of the product in the culture medium, the efficiency of 2,5DKG production is unsatisfactory because there is a large amount of residuald-gluconate at the end of the biotransformation process. Oxidation of 2KG to 2,5DKG is catalyzed by a membrane-bound flavoprotein-cytochromeccomplex: 2-keto-gluconate dehydrogenase (2KGDH). Here, we studied thekgdSLCgenes encoding 2KGDH inG. oxydansNBRC3293 to improve 2,5DKG production byGluconobacterspp. ThekgdS,kgdL, andkgdCgenes correspond to the small, large, and cytochrome subunits of 2KGDH, respectively. ThekgdSLCgenes were cloned into a broad-host-range vector carrying a DNA fragment of the putative promoter region of the membrane-bound alcohol dehydrogenase gene ofG. oxydansfor expression inGluconobacterspp. According to our results, 2KGDH that was purified from the recombinantGluconobactercells showed characteristics nearly the same as those reported previously. We also expressed thekgdSLCgenes in a mutant strain ofGluconobacter japonicusNBRC3271 (formerlyGluconobacter dioxyacetonicusIFO3271) engineered to produce 2KG efficiently from a mixture ofd-glucose andd-gluconate. This mutant strain consumed almost all of the starting materials (d-glucose andd-gluconate) to produce 2,5DKG quantitatively as a seemingly unique metabolite. To our knowledge, this is the first report of aGluconobacterstrain that produces 2,5DKG efficiently and homogeneously.

scholarly journals Regulator RcsB Controls Prodigiosin Synthesis and Various Cellular Processes in Serratia marcescens JNB5-1

2020 ◽  
Vol 87 (2) ◽  
Author(s):  
Xuewei Pan ◽  
Mi Tang ◽  
Jiajia You ◽  
Fei Liu ◽  
Changhao Sun ◽  
...  
Keyword(s):  
Cell Motility ◽  
Serratia Marcescens ◽  
Biofilm Formation ◽  
Capsular Polysaccharide ◽  
Regulatory Mechanism ◽  
Acid Resistance ◽  
Content Type ◽  
Cellular Processes ◽  
Polysaccharide Production ◽  
Insight Into

ABSTRACT Prodigiosin (PG), a red linear tripyrrole pigment normally secreted by Serratia marcescens, has received attention for its reported immunosuppressive, antimicrobial, and anticancer properties. Although several genes have been shown to be important for prodigiosin synthesis, information on the regulatory mechanisms behind this cellular process remains limited. In this work, we identified that the transcriptional regulator RcsB encoding gene BVG90_13250 (rcsB) negatively controlled prodigiosin biosynthesis in S. marcescens. Disruption of rcsB conferred a remarkably increased production of prodigiosin. This phenotype corresponded to negative control of transcription of the prodigiosin-associated pig operon by RcsB, probably by binding to the promoter region of the prodigiosin synthesis positive regulator FlhDC. Moreover, using transcriptomics and further experiments, we revealed that RcsB also controlled some other important cellular processes, including swimming and swarming motilities, capsular polysaccharide production, biofilm formation, and acid resistance (AR), in S. marcescens. Collectively, this work proposes that RcsB is a prodigiosin synthesis repressor in S. marcescens and provides insight into the regulatory mechanism of RcsB in cell motility, capsular polysaccharide production, and acid resistance in S. marcescens. IMPORTANCE RcsB is a two-component response regulator in the Rcs phosphorelay system, and it plays versatile regulatory functions in Enterobacteriaceae. However, information on the function of the RcsB protein in bacteria, especially in S. marcescens, remains limited. In this work, we illustrated experimentally that the RcsB protein was involved in diverse cellular processes in S. marcescens, including prodigiosin synthesis, cell motility, capsular polysaccharide production, biofilm formation, and acid resistance. Additionally, the regulatory mechanism of the RcsB protein in these cellular processes was investigated. In conclusion, this work indicated that RcsB could be a regulator for prodigiosin synthesis and provides insight into the function of the RcsB protein in S. marcescens.

scholarly journals New Insight into HPts as Hubs in Poplar Cytokinin and Osmosensing Multistep Phosphorelays: Cytokinin Pathway Uses Specific HPts

Plants ◽  
2019 ◽  
Vol 8 (12) ◽  
pp. 591 ◽  
Author(s):  
François Héricourt ◽  
Mélanie Larcher ◽  
Françoise Chefdor ◽  
Konstantinos Koudounas ◽  
Inês Carqueijeiro ◽  
...  
Keyword(s):  
Kinase Activity ◽  
Membrane Receptors ◽  
In Planta ◽  
Response Regulators ◽  
Genes Encoding ◽  
The Common ◽  
Almost All ◽  
Activity Dependent ◽  
Two Hybrid ◽  
Insight Into

We have previously identified proteins in poplar which belong to an osmosensing (OS) signaling pathway, called a multistep phosphorelay (MSP). The MSP comprises histidine-aspartate kinases (HK), which act as membrane receptors; histidine phosphotransfer (HPt) proteins, which act as phosphorelay proteins; and response regulators (RR), some of which act as transcription factors. In this study, we identified the HK proteins homologous to the Arabidopsis cytokinin (CK) receptors, which are first partners in the poplar cytokinin MSP, and focused on specificity of these two MSPs (CK and OS), which seem to share the same pool of HPt proteins. Firstly, we isolated five CK HKs from poplar which are homologous to Arabidopsis AHK2, AHK3, and AHK4, namely, HK2, HK3a, HK3b, HK4a, HK4b. These HKs were shown to be functional kinases, as observed in a functional complementation of a yeast HK deleted strain. Moreover, one of these HKs, HK4a, was shown to have kinase activity dependent on the presence of CK. Exhaustive interaction tests between these five CK HKs and the 10 HPts characterized in poplar were performed using two-hybrid and BiFC experiments. The resulting partnership was compared to that previously identified between putative osmosensors HK1a/1b and HPt proteins. Finally, in planta coexpression analysis of genes encoding these potential partners revealed that almost all HPts are coexpressed with CK HKs in four different poplar organs. Overall, these results allowed us to unravel the common and specific partnerships existing between OS and CK MSP in Populus.

scholarly journals Substrate Promiscuity: AglB, the Archaeal Oligosaccharyltransferase, Can Process a Variety of Lipid-Linked Glycans

2013 ◽  
Vol 80 (2) ◽  
pp. 486-496 ◽  
Author(s):  
Chen Cohen-Rosenzweig ◽  
Ziqiang Guan ◽  
Boaz Shaanan ◽  
Jerry Eichler
Keyword(s):  
Chemical Composition ◽  
Halobacterium Salinarum ◽  
Haloferax Volcanii ◽  
Structural Homology ◽  
Haloferax Mediterranei ◽  
Haloarcula Marismortui ◽  
Content Type ◽  
Composition And Structure ◽  
Substrate Promiscuity ◽  
Insight Into

ABSTRACTAcross evolution, N-glycosylation involves oligosaccharyltransferases that transfer lipid-linked glycans to selected Asn residues of target proteins. While these enzymes catalyze similar reactions in each domain, differences exist in terms of the chemical composition, length and degree of phosphorylation of the lipid glycan carrier, the sugar linking the glycan to the lipid carrier, and the composition and structure of the transferred glycan. To gain insight into how oligosaccharyltransferases cope with such substrate diversity, the present study analyzed the archaeal oligosaccharyltransferase AglB from four haloarchaeal species. Accordingly, it was shown that despite processing distinct lipid-linked glycans in their native hosts, AglB fromHaloarcula marismortui,Halobacterium salinarum, andHaloferax mediterraneicould readily replace their counterpart fromHaloferax volcaniiwhen introduced intoHfx. volcaniicells deleted ofaglB. As the four enzymes show significant sequence and apparently structural homology, it appears that the functional similarity of the four AglB proteins reflects the relaxed substrate specificity of these enzymes. Such demonstration of AglB substrate promiscuity is important not only for better understanding of N-glycosylation inArchaeaand elsewhere but also for efforts aimed at transformingHfx. volcaniiinto a glycoengineering platform.

scholarly journals Toxoplasma gondii MAF1b Binds the Host Cell MIB Complex To Mediate Mitochondrial Association

mSphere ◽  
2017 ◽  
Vol 2 (3) ◽  
Author(s):  
Felice D. Kelly ◽  
Brian M. Wei ◽  
Alicja M. Cygan ◽  
Michelle L. Parker ◽  
Martin J. Boulanger ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Host Cell ◽  
Close Association ◽  
Parasitophorous Vacuole ◽  
Secreted Proteins ◽  
Intracellular Pathogens ◽  
Mitochondrial Complex ◽  
Content Type ◽  
The Common ◽  
Insight Into

ABSTRACT Parasites interact intimately with their hosts, and the interactions shape both parties. The common human parasite Toxoplasma gondii replicates exclusively in a vacuole in a host cell and alters its host cell’s environment through secreted proteins. One of these secreted proteins, MAF1b, acts to concentrate mitochondria around the parasite’s vacuole, and this relocalization alters the host immune response. Many other intracellular pathogens also recruit host mitochondria, but the identities of the partners that mediate this interaction have not previously been described in any infection. Here, we show that Toxoplasma MAF1b binds to the multifunctional MIB protein complex on the host mitochondria. Reducing the levels of the proteins in this mitochondrial complex reduces the close association of host cell mitochondria and the parasite’s vacuole. This work provides new insight into a key host-pathogen interaction and identifies possible targets for future therapeutic intervention as well as a more molecular understanding of important biology. Many diverse intracellular pathogens, such as Legionella pneumophila, Chlamydia psittaci, Encephalitozoon sp., and Toxoplasma gondii, manipulate and relocate host cell organelles, including mitochondria. Toxoplasma tachyzoites use a secreted protein, mitochondrial association factor 1b (MAF1b), to drive the association between the host mitochondria and the membrane of the parasitophorous vacuole, in which the parasites grow. The identity of the host partner in this interaction, however, has not previously been identified. By exogenously expressing tagged MAF1b in mouse embryonic fibroblasts, we were able to isolate host cell proteins that specifically interact with MAF1b. We then verified these interactions in the MAF1b-expressing fibroblasts, as well as in the context of parasite infection in human fibroblasts and HeLa cells. The results show that a host cell mitochondrial complex, the mitochondrial intermembrane space bridging (MIB) complex, specifically interacts with MAF1b. We further demonstrate that a version of MAF1b that is deficient in host-mitochondrial association does not efficiently coprecipitate the MIB complex. Validation of the importance of the MAF1b-MIB interaction came from showing that knockdown of two MIB complex components, MIC60 and SAM50, substantially reduces mitochondrial association with the parasitophorous vacuole membrane. This interaction between a secreted membrane-integral parasite protein and a membrane-bound complex of a host organelle represents the first instance of organelle relocalization in which both the host and pathogen molecules are known and provides the foundation for more detailed biochemical studies. IMPORTANCE Parasites interact intimately with their hosts, and the interactions shape both parties. The common human parasite Toxoplasma gondii replicates exclusively in a vacuole in a host cell and alters its host cell’s environment through secreted proteins. One of these secreted proteins, MAF1b, acts to concentrate mitochondria around the parasite’s vacuole, and this relocalization alters the host immune response. Many other intracellular pathogens also recruit host mitochondria, but the identities of the partners that mediate this interaction have not previously been described in any infection. Here, we show that Toxoplasma MAF1b binds to the multifunctional MIB protein complex on the host mitochondria. Reducing the levels of the proteins in this mitochondrial complex reduces the close association of host cell mitochondria and the parasite’s vacuole. This work provides new insight into a key host-pathogen interaction and identifies possible targets for future therapeutic intervention as well as a more molecular understanding of important biology.

What Can Economists Contribute to the Common Good Tradition?

2017 ◽  
Author(s):  
Andrew M. Yuengert
Keyword(s):  
Common Good ◽  
Common Pool Resources ◽  
Economic Approach ◽  
Public And Private ◽  
Private Provision ◽  
The Public ◽  
The Common Good ◽  
The Common ◽  
The Individual ◽  
Insight Into

Although most economists are skeptical of or puzzled by the Catholic concept of the common good, a rejection of the economic approach as inimical to the common good would be hasty and counterproductive. Economic analysis can enrich the common good tradition in four ways. First, economics embodies a deep respect for economic agency and for the effects of policy and institutions on individual agents. Second, economics offers a rich literature on the nature of unplanned order and how it might be shaped by policy. Third, economics offers insight into the public and private provision of various kinds of goods (private, public, common pool resources). Fourth, recent work on the development and logic of institutions and norms emphasizes sustainability rooted in the good of the individual.

scholarly journals Reducing the metabolic energy of walking and running using an unpowered hip exoskeleton

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Tiancheng Zhou ◽  
Caihua Xiong ◽  
Juanjuan Zhang ◽  
Di Hu ◽  
Wenbin Chen ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Design Method ◽  
Metabolic Cost ◽  
Metabolic Energy ◽  
Spring Stiffness ◽  
Spatiotemporal Parameters ◽  
The Common ◽  
Hip Flexion ◽  
Optimal Stiffness ◽  
Insight Into

Abstract Background Walking and running are the most common means of locomotion in human daily life. People have made advances in developing separate exoskeletons to reduce the metabolic rate of walking or running. However, the combined requirements of overcoming the fundamental biomechanical differences between the two gaits and minimizing the metabolic penalty of the exoskeleton mass make it challenging to develop an exoskeleton that can reduce the metabolic energy during both gaits. Here we show that the metabolic energy of both walking and running can be reduced by regulating the metabolic energy of hip flexion during the common energy consumption period of the two gaits using an unpowered hip exoskeleton. Methods We analyzed the metabolic rates, muscle activities and spatiotemporal parameters of 9 healthy subjects (mean ± s.t.d; 24.9 ± 3.7 years, 66.9 ± 8.7 kg, 1.76 ± 0.05 m) walking on a treadmill at a speed of 1.5 m s−1 and running at a speed of 2.5 m s−1 with different spring stiffnesses. After obtaining the optimal spring stiffness, we recruited the participants to walk and run with the assistance from a spring with optimal stiffness at different speeds to demonstrate the generality of the proposed approach. Results We found that the common optimal exoskeleton spring stiffness for walking and running was 83 Nm Rad−1, corresponding to 7.2% ± 1.2% (mean ± s.e.m, paired t-test p < 0.01) and 6.8% ± 1.0% (p < 0.01) metabolic reductions compared to walking and running without exoskeleton. The metabolic energy within the tested speed range can be reduced with the assistance except for low-speed walking (1.0 m s−1). Participants showed different changes in muscle activities with the assistance of the proposed exoskeleton. Conclusions This paper first demonstrates that the metabolic cost of walking and running can be reduced using an unpowered hip exoskeleton to regulate the metabolic energy of hip flexion. The design method based on analyzing the common energy consumption characteristics between gaits may inspire future exoskeletons that assist multiple gaits. The results of different changes in muscle activities provide new insight into human response to the same assistive principle for different gaits (walking and running).

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