Molybdate inhibits mercury methylation capacity of Pseudodesulfovibrio hydrargyri BerOc1 regardless of the growth metabolism.

Molybdate inhibits sulfate respiration in sulfate-reducing bacteria (SRB). It is used as an inhibitor to indirectly evaluate the role of SRB in mercury methylation in the environment. Here, the SRB Pseudodesulfovibrio hydrargyri BerOc1 was used to assess the effect of molybdate on cell growth and mercury methylation under various metabolic conditions.

The Escherichia coli MFS-type transporter genes yhjE, ydiM, and yfcJ are required to produce an active bo3 quinol oxidase.

Heme-copper oxygen reductases are membrane-bound oligomeric complexes that are integral to prokaryotic and eukaryotic aerobic respiratory chains. Biogenesis of these enzymes is complex and requires coordinated assembly of the subunits and their cofactors. Some of the components are involved in the acquisition and integration of different heme and copper (Cu) cofactors into these terminal oxygen reductases.

Consortia cultivation of the Desulfobacterota from macrophyte periphyton: tool for increasing the cultivation of microorganisms involved in mercury methylation.

Invasive macrophytes are a persistent environmental problem in aquatic ecosystems. They also cause potential health issues, since periphyton colonizing their aquatic roots are hot spot of mercury methylation. Because periphytons are at the base of the trophic chain, the produced methylmercury is bioamplified through the food webs.

Effect of exogenous and endogenous sulfide on the production and the export of methylmercury by sulfate-reducing bacteria.

Mercury (Hg) is a global pollutant of environmental and health concern; its methylated form, methylmercury (MeHg), is a potent neurotoxin. Sulfur-containing molecules play a role in MeHg production by microorganisms. While sulfides are considered to limit Hg methylation, sulfate and cysteine were shown to favor this process.

Cysteine Mutants of the Major Facilitator Superfamily-Type Transporter CcoA Provide Insight into Copper Import.

CcoA belongs to the widely distributed bacterial copper (Cu) importer subfamily CalT (co-ike ransporters) of the Major Facilitator Superfamily (MFS) and provides cytoplasmic Cu needed for -type cytochrome oxidase (-Cox) biogenesis. Earlier studies have supported a 12-transmembrane helix (TMH) topology of CcoA with the well-conserved MetxxxMet and HisxxxMet motifs in its TMH7 and TMH8, respectively. Of these residues, Met and His are essential for Cu uptake and -Cox production, whereas Met and Met contribute partly to these processes.

Cu Homeostasis in Bacteria: The Ins and Outs.

Copper (Cu) is an essential trace element for all living organisms and used as cofactor in key enzymes of important biological processes, such as aerobic respiration or superoxide dismutation. However, due to its toxicity, cells have developed elaborate mechanisms for Cu homeostasis, which balance Cu supply for cuproprotein biogenesis with the need to remove excess Cu. This review summarizes our current knowledge on bacterial Cu homeostasis with a focus on Gram-negative bacteria and describes the multiple strategies that bacteria use for uptake, storage and export of Cu.

Comparative differential cuproproteomes of Rhodobacter capsulatus reveal novel copper homeostasis related proteins.

Copper (Cu) is an essential, but toxic, micronutrient for living organisms and cells have developed sophisticated response mechanisms towards both the lack and the excess of Cu in their environments. In this study, we achieved a global view of Cu-responsive changes in the prokaryotic model organism Rhodobacter capsulatus using label-free quantitative differential proteomics. Semi-aerobically grown cells under heterotrophic conditions in minimal medium (∼0.

Genome insights of mercury methylation among Desulfovibrio and Pseudodesulfovibrio strains.

Mercury methylation converts inorganic mercury into the toxic methylmercury, and the consequences of this transformation are worrisome for human health and the environment. This process is performed by anaerobic microorganisms, such as several strains related to Pseudodesulfovibrio and Desulfovibrio genera. In order to provide new insights into the molecular mechanisms of mercury methylation, we performed a comparative genomic analysis on mercury methylators and non-methylators from (Pseudo)Desulfovibrio strains.

Cu Transport by the Extended Family of CcoA-like Transporters (CalT) in Proteobacteria.

Comparative genomic studies of the bacterial MFS-type copper importer CcoA, required for cbb-type cytochrome c oxidase (cbb-Cox) biogenesis, revealed a widespread CcoA-like transporters (CalT) family, containing the conserved CcoA Cu-binding MxxxM and HxxxM motifs. Surprisingly, this family also included the RfnT-like proteins, earlier suggested to transport riboflavin. However, presence of the Cu-binding motifs in these proteins raised the possibility that they might be Cu transporters.

A Copper Relay System Involving Two Periplasmic Chaperones Drives cbb-Type Cytochrome c Oxidase Biogenesis in Rhodobacter capsulatus.

PccA and SenC are periplasmic copper chaperones required for the biogenesis of cbb-type cytochrome c oxidase ( cbb-Cox) in Rhodobacter capsulatus at physiological Cu concentrations. However, both proteins are dispensable for cbb-Cox assembly when the external Cu concentration is high. PccA and SenC bind Cu using Met and His residues and Cys and His residues as ligands, respectively, and both proteins form a complex during cbb-Cox biogenesis.

Widespread Distribution and Functional Specificity of the Copper Importer CcoA: Distinct Cu Uptake Routes for Bacterial Cytochrome Oxidases.

Cytochrome oxidases are members of the heme-copper oxidase superfamily. These enzymes have different subunits, cofactors, and primary electron acceptors, yet they all contain identical heme-copper (Cu) binuclear centers within their catalytic subunits. The uptake and delivery pathways of the Cu atom incorporated into this active site, where oxygen is reduced to water, are not well understood.

Absence of Thiol-Disulfide Oxidoreductase DsbA Impairs -Type Cytochrome Oxidase Biogenesis in .

The thiol-disulfide oxidoreductase DsbA carries out oxidative folding of extra-cytoplasmic proteins by catalyzing the formation of intramolecular disulfide bonds. It has an important role in various cellular functions, including cell division. The purple non-sulfur bacterium mutants lacking DsbA show severe temperature-sensitive and medium-dependent respiratory growth defects.

Biogenesis of the bacterial cytochrome oxidase: Active subcomplexes support a sequential assembly model.

The oxidase has a high affinity for oxygen and is required for growth of bacteria, including pathogens, in oxygen-limited environments. However, the assembly of this oxidase is poorly understood. Most are composed of four subunits: the catalytic CcoN subunit, the two cytochrome subunits (CcoO and CcoP) involved in electron transfer, and the small CcoQ subunit with an unclear function.

The thioreduction component CcmG confers efficiency and the heme ligation component CcmH ensures stereo-specificity during cytochrome maturation.

In many Gram-negative bacteria, including cytochrome maturation (Ccm) is carried out by a membrane-integral machinery composed of nine proteins (CcmA to I). During this process, the periplasmic thiol-disulfide oxidoreductase DsbA is thought to catalyze the formation of a disulfide bond between the Cys residues at the apocytochrome heme-binding site (CCH). Subsequently, a Ccm-specific thioreductive pathway involving CcmG and CcmH reduces this disulfide bond to allow covalent heme ligation.

Uncovering the Transmembrane Metal Binding Site of the Novel Bacterial Major Facilitator Superfamily-Type Copper Importer CcoA.

Unlabelled: Uptake and trafficking of metals and their delivery to their respective metalloproteins are important processes. Cells need precise control of each step to avoid exposure to excessive metal concentrations and their harmful consequences. Copper (Cu) is a required micronutrient used as a cofactor in proteins.

Cooperation between two periplasmic copper chaperones is required for full activity of the cbb3 -type cytochrome c oxidase and copper homeostasis in Rhodobacter capsulatus.

Copper (Cu) is an essential micronutrient that functions as a cofactor in several important enzymes, such as respiratory heme-copper oxygen reductases. Yet, Cu is also toxic and therefore cells engage a highly coordinated Cu uptake and delivery system to prevent the accumulation of toxic Cu concentrations. In this study, we analyzed Cu delivery to the cbb3 -type cytochrome c oxidase (cbb3 -Cox) of Rhodobacter capsulatus.

Intermonomer electron transfer between the b hemes of heterodimeric cytochrome bc(1).

The ubihydroquinone:cytochrome c oxidoreductase, or cytochrome bc1, is a central component of respiratory and photosynthetic energy transduction pathways in many organisms. It contributes to the generation of membrane potential and proton gradient used for cellular energy (ATP) production. The three-dimensional structures of cytochrome bc1 show a homodimeric organization of its three catalytic subunits.

A robust genetic system for producing heterodimeric native and mutant cytochrome bc(1).

The ubihydroquinone:cytochrome c oxidoreductase, or cytochrome bc1, is central to the production of ATP by oxidative phosphorylation and photophosphorylation in many organisms. Its three-dimensional structure depicts it as a homodimer with each monomer composed of the Fe-S protein, cytochrome b, and cytochrome c1 subunits. Recent genetic approaches successfully produced heterodimeric variants of this enzyme, providing insights into its mechanism of function.

Molecular mechanisms of superoxide production by complex III: a bacterial versus human mitochondrial comparative case study.

In this mini review, we briefly survey the molecular processes that lead to reactive oxygen species (ROS) production by the respiratory complex III (CIII or cytochrome bc1). In particular, we discuss the "forward" and "reverse" electron transfer pathways that lead to superoxide generation at the quinol oxidation (Qo) site of CIII, and the components that affect these reactions. We then describe and compare the properties of a bacterial (Rhodobacter capsulatus) mutant enzyme producing ROS with its mitochondrial (human cybrids) counterpart associated with a disease.

Coproporphyrin III excretion identifies the anaerobic coproporphyrinogen III oxidase HemN as a copper target in the Cu⁺-ATPase mutant copA⁻ of Rubrivivax gelatinosus.

Two genes encoding structurally similar Copper P1B -type ATPases can be identified in several genomes. Notwithstanding the high sequence and structural similarities these ATPases held, it has been suggested that they fulfil distinct physiological roles. In deed, we have shown that the Cu(+) -ATPase CtpA is required only for the activity of cuproproteins in the purple bacterium Rubrivivax gelatinosus; herein, we show that CopA is not directly required for cytochrome c oxidase but is vital for copper tolerance.

Recent advances in cytochrome bc(1): inter monomer electronic communication?

The ubihydroquinone: cytochrome c oxidoreductase, or cytochrome bc(1), is a central component of photosynthetic and respiratory energy transduction pathways in many organisms. It contributes to the generation of membrane potential and proton gradient used for cellular energy production (ATP). The three-dimensional structures of cytochrome bc(1) indicate that its two monomers are intertwined to form a symmetrical homodimer.

CtpA, a copper-translocating P-type ATPase involved in the biogenesis of multiple copper-requiring enzymes.

The ctpA (ccoI) gene product, a putative inner membrane copper-translocating P1B-type ATPase present in many bacteria, has been shown to be involved only in the cbb(3) assembly in Rhodobacter capsulatus and Bradyrhizobium japonicum. ctpA was disrupted in Rubrivivax gelatinosus, and the mutants showed a drastic decrease in both cbb(3) and caa(3) oxidase activities. Inactivation of ctpA results also in a decrease in the amount of the nitrous oxide reductase, NosZ.

Adaptation to oxygen: role of terminal oxidases in photosynthesis initiation in the purple photosynthetic bacterium, Rubrivivax gelatinosus.

The appearance of oxygen in the Earth's atmosphere via oxygenic photosynthesis required strict anaerobes and obligate phototrophs to cope with the presence of this toxic molecule. Here we show that in the anoxygenic phototroph Rubrivivax gelatinosus, the terminal oxidases (cbb(3), bd, and caa(3)) expand the range of ambient oxygen tensions under which the organism can initiate photosynthesis. Unlike the wild type, the cbb(3)(-)/bd(-) double mutant can start photosynthesis only in deoxygenated medium or when oxygen is removed, either by sparging cultures with nitrogen or by co-inoculation with strict aerobes bacteria.