scholarly journals The Complete Genome Sequence of Clostridium aceticum: a Missing Link between Rnf- and Cytochrome-Containing Autotrophic Acetogens

mBio ◽  
2015 ◽  
Vol 6 (5) ◽  
Author(s):  
Anja Poehlein ◽  
Martin Cebulla ◽  
Marcus M. Ilg ◽  
Frank R. Bengelsdorf ◽  
Bettina Schiel-Bengelsdorf ◽  
...  
Keyword(s):  
Electron Transport Chain ◽  
Proton Translocation ◽  
Acetobacterium Woodii ◽  
Content Type ◽  
Moorella Thermoacetica ◽  
Sustainable Products ◽  
Transport Chain ◽  
Acetogenic Bacteria ◽  
Biotechnological Processes ◽  
Clostridium Aceticum

ABSTRACTClostridium aceticumwas the first isolated autotrophic acetogen, converting CO2plus H2or syngas to acetate. Its genome has now been completely sequenced and consists of a 4.2-Mbp chromosome and a small circular plasmid of 5.7 kbp. Sequence analysis revealed major differences from other autotrophic acetogens.C. aceticumcontains an Rnf complex for energy conservation (via pumping protons or sodium ions). Such systems have also been found inC. ljungdahliiandAcetobacterium woodii. However,C. aceticumalso contains a cytochrome, as doesMoorella thermoacetica, which has been proposed to be involved in the generation of a proton gradient. Thus,C. aceticumseems to represent a link between Rnf- and cytochrome-containing autotrophic acetogens. InC. aceticum, however, the cytochrome is probably not involved in an electron transport chain that leads to proton translocation, as no genes for quinone biosynthesis are present in the genome.IMPORTANCEAutotrophic acetogenic bacteria are receiving more and more industrial focus, as CO2plus H2as well as syngas are interesting new substrates for biotechnological processes. They are both cheap and abundant, and their use, if it results in sustainable products, also leads to reduction of greenhouse gases.Clostridium aceticumcan use both gas mixtures, is phylogenetically not closely related to the commonly used species, and may thus become an even more attractive workhorse. In addition, its energy metabolism, which is characterized here, and the ability to synthesize cytochromes might offer new targets for improving the ATP yield by metabolic engineering and thus allow use ofC. aceticumfor production of compounds by pathways that currently present challenges for energy-limited acetogens.

scholarly journals Physiological Evidence for Isopotential Tunneling in the Electron Transport Chain of Methane-Producing Archaea

2017 ◽  
Vol 83 (18) ◽  
Author(s):  
Nikolas Duszenko ◽  
Nicole R. Buan
Keyword(s):  
Escherichia Coli ◽  
Electron Transport ◽  
Stationary Phase ◽  
Exponential Growth ◽  
Electron Transport Chain ◽  
Methanosarcina Barkeri ◽  
Metabolic Efficiency ◽  
Methanosarcina Acetivorans ◽  
Content Type ◽  
Transport Chain

ABSTRACT Many, but not all, organisms use quinones to conserve energy in their electron transport chains. Fermentative bacteria and methane-producing archaea (methanogens) do not produce quinones but have devised other ways to generate ATP. Methanophenazine (MPh) is a unique membrane electron carrier found in Methanosarcina species that plays the same role as quinones in the electron transport chain. To extend the analogy between quinones and MPh, we compared the MPh pool sizes between two well-studied Methanosarcina species, Methanosarcina acetivorans C2A and Methanosarcina barkeri Fusaro, to the quinone pool size in the bacterium Escherichia coli. We found the quantity of MPh per cell increases as cultures transition from exponential growth to stationary phase, and absolute quantities of MPh were 3-fold higher in M. acetivorans than in M. barkeri. The concentration of MPh suggests the cell membrane of M. acetivorans, but not of M. barkeri, is electrically quantized as if it were a single conductive metal sheet and near optimal for rate of electron transport. Similarly, stationary (but not exponentially growing) E. coli cells also have electrically quantized membranes on the basis of quinone content. Consistent with our hypothesis, we demonstrated that the exogenous addition of phenazine increases the growth rate of M. barkeri three times that of M. acetivorans. Our work suggests electron flux through MPh is naturally higher in M. acetivorans than in M. barkeri and that hydrogen cycling is less efficient at conserving energy than scalar proton translocation using MPh. IMPORTANCE Can we grow more from less? The ability to optimize and manipulate metabolic efficiency in cells is the difference between commercially viable and nonviable renewable technologies. Much can be learned from methane-producing archaea (methanogens) which evolved a successful metabolic lifestyle under extreme thermodynamic constraints. Methanogens use highly efficient electron transport systems and supramolecular complexes to optimize electron and carbon flow to control biomass synthesis and the production of methane. Worldwide, methanogens are used to generate renewable methane for heat, electricity, and transportation. Our observations suggest Methanosarcina acetivorans, but not Methanosarcina barkeri, has electrically quantized membranes. Escherichia coli, a model facultative anaerobe, has optimal electron transport at the stationary phase but not during exponential growth. This study also suggests the metabolic efficiency of bacteria and archaea can be improved using exogenously supplied lipophilic electron carriers. The enhancement of methanogen electron transport through methanophenazine has the potential to increase renewable methane production at an industrial scale.

scholarly journals Vibrio cholerae VciB Mediates Iron Reduction

2017 ◽  
Vol 199 (12) ◽  
Author(s):  
Eric D. Peng ◽  
Shelley M. Payne
Keyword(s):  
Electron Transport ◽  
Vibrio Cholerae ◽  
Ferrous Iron ◽  
Electron Transport Chain ◽  
Iron Reduction ◽  
Iron Transport ◽  
Ferric Iron ◽  
Transport Systems ◽  
Content Type ◽  
Transport Chain

ABSTRACT Vibrio cholerae is the causative agent of the severe diarrheal disease cholera. V. cholerae thrives within the human host, where it replicates to high numbers, but it also persists within the aquatic environments of ocean and brackish water. To survive within these nutritionally diverse environments, V. cholerae must encode the necessary tools to acquire the essential nutrient iron in all forms it may encounter. A prior study of systems involved in iron transport in V. cholerae revealed the existence of vciB, which, while unable to directly transport iron, stimulates the transport of iron through ferrous (Fe2+) iron transport systems. We demonstrate here a role for VciB in V. cholerae in which VciB stimulates the reduction of Fe3+ to Fe2+, which can be subsequently transported into the cell with the ferrous iron transporter Feo. Iron reduction is independent of functional iron transport but is associated with the electron transport chain. Comparative analysis of VciB orthologs suggests a similar role for other proteins in the VciB family. Our data indicate that VciB is a dimer located in the inner membrane with three transmembrane segments and a large periplasmic loop. Directed mutagenesis of the protein reveals two highly conserved histidine residues required for function. Taken together, our results support a model whereby VciB reduces ferric iron using energy from the electron transport chain. IMPORTANCE Vibrio cholerae is a prolific human pathogen and environmental organism. The acquisition of essential nutrients such as iron is critical for replication, and V. cholerae encodes a number of mechanisms to use iron from diverse environments. Here, we describe the V. cholerae protein VciB that increases the reduction of oxidized ferric iron (Fe3+) to the ferrous form (Fe2+), thus promoting iron acquisition through ferrous iron transporters. Analysis of VciB orthologs in Burkholderia and Aeromonas spp. suggest that they have a similar activity, allowing a functional assignment for this previously uncharacterized protein family. This study builds upon our understanding of proteins known to mediate iron reduction in bacteria.

scholarly journals Genomic, Proteomic, and Biochemical Analysis of the Organohalide Respiratory Pathway in Desulfitobacterium dehalogenans

2014 ◽  
Vol 197 (5) ◽  
pp. 893-904 ◽  
Author(s):  
Thomas Kruse ◽  
Bram A. van de Pas ◽  
Ariane Atteia ◽  
Klaas Krab ◽  
Wilfred R. Hagen ◽  
...  
Keyword(s):  
Electron Transport ◽  
Electron Acceptor ◽  
Electron Transport Chain ◽  
Biochemical Analysis ◽  
Active Components ◽  
Organohalide Respiration ◽  
Content Type ◽  
Membrane Complex ◽  
Redox Active ◽  
Transport Chain

Desulfitobacterium dehalogenansis able to grow by organohalide respiration using 3-chloro-4-hydroxyphenyl acetate (Cl-OHPA) as an electron acceptor. We used a combination of genome sequencing, biochemical analysis of redox active components, and shotgun proteomics to study elements of the organohalide respiratory electron transport chain. The genome ofDesulfitobacterium dehalogenansJW/IU-DC1Tconsists of a single circular chromosome of 4,321,753 bp with a GC content of 44.97%. The genome contains 4,252 genes, including six rRNA operons and six predicted reductive dehalogenases. One of the reductive dehalogenases, CprA, is encoded by a well-characterizedcprTKZEBACDgene cluster. Redox active components were identified in concentrated suspensions of cells grown on formate and Cl-OHPA or formate and fumarate, using electron paramagnetic resonance (EPR), visible spectroscopy, and high-performance liquid chromatography (HPLC) analysis of membrane extracts. In cell suspensions, these components were reduced upon addition of formate and oxidized after addition of Cl-OHPA, indicating involvement in organohalide respiration. Genome analysis revealed genes that likely encode the identified components of the electron transport chain from formate to fumarate or Cl-OHPA. Data presented here suggest that the first part of the electron transport chain from formate to fumarate or Cl-OHPA is shared. Electrons are channeled from an outward-facing formate dehydrogenase via menaquinones to a fumarate reductase located at the cytoplasmic face of the membrane. When Cl-OHPA is the terminal electron acceptor, electrons are transferred from menaquinones to outward-facing CprA, via an as-yet-unidentified membrane complex, and potentially an extracellular flavoprotein acting as an electron shuttle between the quinol dehydrogenase membrane complex and CprA.

scholarly journals Tolerance and Metabolic Response of Acetogenic Bacteria toward Oxygen

2002 ◽  
Vol 68 (2) ◽  
pp. 1005-1009 ◽  
Author(s):  
Arno Karnholz ◽  
Kirsten K�sel ◽  
Anita G��ner ◽  
Andreas Schramm ◽  
Harold L. Drake
Keyword(s):  
Metabolic Response ◽  
Nadh Oxidase ◽  
Lag Phase ◽  
Acetobacterium Woodii ◽  
Acetyl Coenzyme A ◽  
Moorella Thermoacetica ◽  
Cell Extracts ◽  
Low Concentrations ◽  
Acetogenic Bacteria ◽  
Thermoanaerobacter Kivui

ABSTRACT The acetogens Sporomusa silvacetica, Moorella thermoacetica, Clostridium magnum, Acetobacterium woodii, and Thermoanaerobacter kivui (i) grew in both semisolid and liquid cultivation media containing O2 and (ii) consumed small amounts of O2. Low concentrations of O2 caused a lag phase in growth but did not alter the ability of these acetogens to synthesize acetate via the acetyl coenzyme A pathway. Cell extracts of S. silvacetica, M. thermoacetica, and C. magnum contained peroxidase and NADH oxidase activities; catalase and superoxide dismutase activities were not detected.

scholarly journals Insights into the Fundamental Physiology of the Uncultured Fe-Oxidizing BacteriumLeptothrix ochracea

2018 ◽  
Vol 84 (9) ◽  
Author(s):  
E. J. Fleming ◽  
T. Woyke ◽  
R. A. Donatello ◽  
M. M. M. Kuypers ◽  
A. Sczyrba ◽  
...  
Keyword(s):  
Electron Transport ◽  
Single Cell ◽  
Electron Transport Chain ◽  
Natural Waters ◽  
Iron Oxidation ◽  
Complex Iii ◽  
Total Carbon ◽  
Bisphosphate Carboxylase ◽  
Content Type ◽  
Transport Chain

ABSTRACTLeptothrix ochraceais known for producing large volumes of iron oxyhydroxide sheaths that alter wetland biogeochemistry. For over a century, these delicate structures have fascinated microbiologists and geoscientists. BecauseL. ochraceastill resists long-termin vitroculture, the debate regarding its metabolic classification dates back to 1885. We developed a novel culturing technique forL. ochraceausingin situnatural waters and coupled this with single-cell genomics and nanoscale secondary-ion mass spectrophotometry (nanoSIMS) to probeL. ochracea's physiology. In microslide culturesL. ochraceadoubled every 5.7 h and had an absolute growth requirement for ferrous iron, the genomic capacity for iron oxidation, and a branched electron transport chain with cytochromes putatively involved in lithotrophic iron oxidation. Additionally, its genome encoded several electron transport chain proteins, including a molybdopterin alternative complex III (ACIII), a cytochromebdoxidase reductase, and several terminal oxidase genes.L. ochraceacontained two key autotrophic proteins in the Calvin-Benson-Bassham cycle, a form II ribulose bisphosphate carboxylase, and a phosphoribulose kinase.L. ochraceaalso assimilated bicarbonate, although calculations suggest that bicarbonate assimilation is a small fraction of its total carbon assimilation. Finally,L. ochracea's fundamental physiology is a hybrid of those of the chemolithotrophicGallionella-type iron-oxidizing bacteria and the sheathed, heterotrophic filamentous metal-oxidizing bacteria of theLeptothrix-Sphaerotilusgenera. This allowsL. ochraceato inhabit a unique niche within the neutrophilic iron seeps.IMPORTANCELeptothrix ochraceawas one of three groups of organisms that Sergei Winogradsky used in the 1880s to develop his hypothesis on chemolithotrophy.L. ochraceacontinues to resist cultivation and appears to have an absolute requirement for organic-rich waters, suggesting that its true physiology remains unknown. Further,L. ochraceais an ecological engineer; a fewL. ochraceacells can generate prodigious volumes of iron oxyhydroxides, changing the ecosystem's geochemistry and ecology. Therefore, to determineL. ochracea's basic physiology, we employed new single-cell techniques to demonstrate thatL. ochraceaoxidizes iron to generate energy and, despite having predicted genes for autotrophic growth, assimilates a fraction of the total CO2that autotrophs do. Although not a true chemolithoautotroph,L. ochracea's physiological strategy allows it to be flexible and to extensively colonize iron-rich wetlands.

scholarly journals Neutralization of Mitochondrial Superoxide by Superoxide Dismutase 2 Promotes Bacterial Clearance and Regulates Phagocyte Numbers in Zebrafish

2014 ◽  
Vol 83 (1) ◽  
pp. 430-440 ◽  
Author(s):  
E. M. Peterman ◽  
C. Sullivan ◽  
M. F. Goody ◽  
I. Rodriguez-Nunez ◽  
J. A. Yoder ◽  
...  
Keyword(s):  
Superoxide Dismutase ◽  
Electron Transport ◽  
Mitochondrial Dysfunction ◽  
Electron Transport Chain ◽  
Bacterial Burden ◽  
Content Type ◽  
Mitochondrial Ros ◽  
Transport Chain ◽  
Severe Infections ◽  
Superoxide Dismutase 2

Mitochondria are known primarily as the location of the electron transport chain and energy production in cells. More recently, mitochondria have been shown to be signaling centers for apoptosis and inflammation. Reactive oxygen species (ROS) generated as by-products of the electron transport chain within mitochondria significantly impact cellular signaling pathways. Because of the toxic nature of ROS, mitochondria possess an antioxidant enzyme, superoxide dismutase 2 (SOD2), to neutralize ROS. If mitochondrial antioxidant enzymes are overwhelmed during severe infections, mitochondrial dysfunction can occur and lead to multiorgan failure or death.Pseudomonas aeruginosais an opportunistic pathogen that can infect immunocompromised patients. Infochemicals and exotoxins associated withP. aeruginosaare capable of causing mitochondrial dysfunction. In this work, we describe the roles of SOD2 and mitochondrial ROS regulation in the zebrafish innate immune response toP. aeruginosainfection.sod2is upregulated in mammalian macrophages and neutrophils in response to lipopolysaccharidein vitro, andsod2knockdown in zebrafish results in an increased bacterial burden. Further investigation revealed that phagocyte numbers are compromised in Sod2-deficient zebrafish. Addition of the mitochondrion-targeted ROS-scavenging chemical MitoTEMPO rescues neutrophil numbers and reduces the bacterial burden in Sod2-deficient zebrafish. Our work highlights the importance of mitochondrial ROS regulation by SOD2 in the context of innate immunity and supports the use of mitochondrion-targeted ROS scavengers as potential adjuvant therapies during severe infections.

scholarly journals Nitric Oxide Protects Bacteria from Aminoglycosides by Blocking the Energy-Dependent Phases of Drug Uptake

2011 ◽  
Vol 55 (5) ◽  
pp. 2189-2196 ◽  
Author(s):  
Bruce D. McCollister ◽  
Matthew Hoffman ◽  
Maroof Husain ◽  
Andrés Vázquez-Torres
Keyword(s):  
Nitric Oxide ◽  
Electron Transport ◽  
Electron Transport Chain ◽  
Respiratory Activity ◽  
Inflammatory Responses ◽  
Drug Uptake ◽  
No Donor ◽  
Content Type ◽  
Transport Chain ◽  
Energy Dependent

ABSTRACTOur investigations have identified a mechanism by which exogenous production of nitric oxide (NO) induces resistance of Gram-positive and -negative bacteria to aminoglycosides. An NO donor was found to protectSalmonellaspp. against structurally diverse classes of aminoglycosides of the 4,6-disubstituted 2-deoxystreptamine group. Likewise, NO generated enzymatically by inducible NO synthase of gamma interferon-primed macrophages protected intracellularSalmonellaagainst the cytotoxicity of gentamicin. NO levels that elicited protection against aminoglycosides repressedSalmonellarespiratory activity. NO nitrosylated terminal quinol cytochrome oxidases, without exerting long-lasting inhibition of NADH dehydrogenases of the electron transport chain. The NO-mediated repression of respiratory activity blocked both energy-dependent phases I and II of aminoglycoside uptake but not the initial electrostatic interaction of the drug with the bacterial cell envelope. As seen inSalmonella, the NO-dependent inhibition of the electron transport chain also afforded aminoglycoside resistance to the clinically important pathogensPseudomonas aeruginosaandStaphylococcus aureus. Together, these findings provide evidence for a model in which repression of aerobic respiration by NO fluxes associated with host inflammatory responses can reduce drug uptake, thus promoting resistance to several members of the aminoglycoside family in phylogenetically diverse bacteria.

scholarly journals Staphylococcus epidermidis SrrAB Regulates Bacterial Growth and Biofilm Formation Differently under Oxic and Microaerobic Conditions

2014 ◽  
Vol 197 (3) ◽  
pp. 459-476 ◽  
Author(s):  
Youcong Wu ◽  
Yang Wu ◽  
Tao Zhu ◽  
Haiyan Han ◽  
Huayong Liu ◽  
...  
Keyword(s):  
Electron Transport ◽  
Staphylococcus Epidermidis ◽  
Biofilm Formation ◽  
Electron Transport Chain ◽  
Regulatory Function ◽  
Dependent Manner ◽  
Mobility Shift ◽  
Content Type ◽  
Transport Chain ◽  
Microaerobic Conditions

SrrAB expression inStaphylococcus epidermidisstrain 1457 (SE1457) was upregulated during a shift from oxic to microaerobic conditions. AnsrrAdeletion (ΔsrrA) mutant was constructed for studying the regulatory function of SrrAB. The deletion resulted in retarded growth and abolished biofilm formation bothin vitroandin vivoand under both oxic and microaerobic conditions. Associated with the reduced biofilm formation, the ΔsrrAmutant produced much less polysaccharide intercellular adhesion (PIA) and showed decreased initial adherence capacity. Microarray analysis showed that thesrrAmutation affected transcription of 230 genes under microaerobic conditions, and 51 genes under oxic conditions. Quantitative real-time PCR confirmed this observation and showed downregulation of genes involved in maintaining the electron transport chain by supporting cytochrome and quinol-oxidase assembly (e.g.,qoxBandctaA) and in anaerobic metabolism (e.g.,pflBAandnrdD). In the ΔsrrAmutant, the expression of the biofilm formation-related geneicaRwas upregulated under oxic conditions and downregulated under microaerobic conditions, whereasicaAwas downregulated under both conditions. An electrophoretic mobility shift assay further revealed that phosphorylated SrrA bound to the promoter regions oficaR,icaA,qoxB, andpflBA, as well as its own promoter region. These findings demonstrate that inS. epidermidisSrrAB is an autoregulator and regulates biofilm formation in anica-dependent manner. Under oxic conditions, SrrAB modulates electron transport chain activity by positively regulatingqoxBACDtranscription. Under microaerobic conditions, it regulates fermentation processes and DNA synthesis by modulating the expression of both thepfloperon andnrdDG.

Proton Translocation Linked to the Activity of the Bi-Trans-membrane Electron Transport Chain

1995 ◽  
Vol 319 (1) ◽  
pp. 36-48 ◽  
Author(s):  
D. Marzulli ◽  
G. Lapiana ◽  
L. Cafagno ◽  
E. Fransvea ◽  
N.E. Lofrumento
Keyword(s):  
Electron Transport ◽  
Electron Transport Chain ◽  
Proton Translocation ◽  
Transport Chain

scholarly journals Alanine, a Novel Growth Substrate for the Acetogenic BacteriumAcetobacterium woodii

2018 ◽  
Vol 84 (23) ◽  
Author(s):  
Judith Dönig ◽  
Volker Müller
Keyword(s):  
Amino Acids ◽  
Ph Regulation ◽  
Anaerobic Bacteria ◽  
Strictly Anaerobic ◽  
Growth Substrate ◽  
Acetobacterium Woodii ◽  
Content Type ◽  
Important Group ◽  
Acetogenic Bacteria ◽  
A Minor

ABSTRACTAcetogenic bacteria are an ecophysiologically important group of strictly anaerobic bacteria that grow lithotrophically on H2plus CO2or on CO or heterotrophically on different substrates such as sugars, alcohols, aldehydes, or acids. Amino acids are rarely used. Here, we describe that the model acetogenAcetobacterium woodiican use alanine as the sole carbon and energy source, which is in contrast to the description of the type strain. The alanine degradation genes have been identified and characterized. A key to alanine degradation is an alanine dehydrogenase which has been characterized biochemically. The resulting pyruvate is further degraded to acetate by the known pathways involving the Wood-Ljungdahl pathway. Our studies culminate in a metabolic and bioenergetic scheme for alanine-dependent acetogenesis inA. woodii.IMPORTANCEPeptides and amino acids are widespread in nature, but there are only a few reports that demonstrated use of amino acids as carbon and energy sources by acetogenic bacteria, a central and important group in the anaerobic food web. Our finding thatA. woodiican perform alanine oxidation coupled to reduction of carbon dioxide not only increases the number of substrates that can be used by this model acetogen but also raises the possibility that other acetogens may also be able to use alanine. Indeed, the alanine genes are also present in at least two more acetogens, for which growth on alanine has not been reported so far. Alanine may be a promising substrate for industrial fermentations, since acid formation goes along with the production of a base (NH3) and pH regulation is a minor issue.

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