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Environmental Science & Technology Dec 2016Microbial conversion of inorganic mercury (IHg) to methylmercury (MeHg) is a significant environmental concern because of the bioaccumulation and biomagnification of...
Microbial conversion of inorganic mercury (IHg) to methylmercury (MeHg) is a significant environmental concern because of the bioaccumulation and biomagnification of toxic MeHg in the food web. Laboratory incubation studies have shown that, despite the presence of large quantities of IHg in cell cultures, MeHg biosynthesis often reaches a plateau or a maximum within hours or a day by an as yet unexplained mechanism. Here we report that mercuric Hg(II) can be taken up rapidly by cells of Desulfovibrio desulfuricans ND132, but a large fraction of the Hg(II) is unavailable for methylation because of strong cellular sorption. Thiols, such as cysteine, glutathione, and penicillamine, added either simultaneously with Hg(II) or after cells have been exposed to Hg(II), effectively desorb or mobilize the bound Hg(II), leading to a substantial increase in MeHg production. The amount of thiol-desorbed Hg(II) is strongly correlated to the amount of MeHg produced (r = 0.98). However, cells do not preferentially take up Hg(II)-thiol complexes, but Hg(II)-ligand exchange between these complexes and the cell-associated proteins likely constrains Hg(II) uptake and methylation. We suggest that, aside from aqueous chemical speciation of Hg(II), binding and exchange of Hg(II) between cells and complexing ligands such as thiols and naturally dissolved organics in solution is an important controlling mechanism of Hg(II) bioavailability, which should be considered when predicting MeHg production in the environment.
Topics: Biological Availability; Desulfovibrio desulfuricans; Mercury; Methylmercury Compounds; Sulfhydryl Compounds; Water Pollutants, Chemical
PubMed: 27993064
DOI: 10.1021/acs.est.6b04041 -
Revista Argentina de Microbiologia 2017Two cases of insidious bacteremia by uncommon curve and spiral-shaped, motile anaerobic gram-negative rods are presented. Both of them were of an unclear origin and...
Two cases of insidious bacteremia by uncommon curve and spiral-shaped, motile anaerobic gram-negative rods are presented. Both of them were of an unclear origin and occurred in immunosuppressed patients with simultaneous diseases. The key tests for the identification of Anaerobiospirillum were its micromorphology, a strictly anaerobic condition, negative catalase activity, the special-potency disk profile, glucose fermentation, and β-NAG production. Desulfovibrio species was identified by all the above preliminary tests but with a different disk profile, as well as for being asaccharolytic and desulfoviridin and HS producer. We here alert about the resistance or intermediate susceptibility of Anaerobiospirillum succiniciproducens against antimicrobial agents, such as metronidazole, one of the first-line drugs used for the treatment of anaerobic gram-negative infections. Aminopenicillins with β-lactamase-inhibitor combinations and imipenem were active for this agent. Desulfovibrio desulfuricans was β-lactamase producer and resistant to cephalosporins, while metronidazole, imipenem and levofloxacin were active. A reliable identification of these microorganisms is important for establishing the best therapeutic scheme.
Topics: Anaerobiospirillum; Anti-Bacterial Agents; Bacteremia; Desulfovibrio desulfuricans; Gram-Negative Bacterial Infections; Humans; Immunocompromised Host
PubMed: 28506633
DOI: 10.1016/j.ram.2016.12.008 -
Bioresource Technology Jul 2017In this work a novel bioprocess for hydrogenation of CO to formate was developed, using whole cell catalysis by a sulfate-reducing bacterium. Three Desulfovibrio species...
In this work a novel bioprocess for hydrogenation of CO to formate was developed, using whole cell catalysis by a sulfate-reducing bacterium. Three Desulfovibrio species were tested (D. vulgaris Hildenborough, D. alaskensis G20, and D. desulfuricans ATCC 27774), of which D. desulfuricans showed the highest activity, producing 12mM of formate in batch, with a production rate of 0.09mMh. Gene expression analysis indicated that among the three formate dehydrogenases and five hydrogenases, the cytoplasmic FdhAB and the periplasmic [FeFe] HydAB are the main enzymes expressed in D. desulfuricans in these conditions. The new bioprocess for continuous formate production by D. desulfuricans had a maximum specific formate production rate of 14mMgh, and more than 45mM of formate were obtained with a production rate of 0.40mMh. This is the first report of a continuous process for biocatalytic formate production.
Topics: Biocatalysis; Carbon Dioxide; Desulfovibrio; Formate Dehydrogenases; Formates; Hydrogenation
PubMed: 28365342
DOI: 10.1016/j.biortech.2017.03.091 -
International Journal of Systematic and... Jun 2019The sulfate-reducing, mercury-methylating strain ND132 was isolated from the brackish anaerobic bottom sediments of Chesapeake Bay, USA. Capable of high levels of...
The sulfate-reducing, mercury-methylating strain ND132 was isolated from the brackish anaerobic bottom sediments of Chesapeake Bay, USA. Capable of high levels of mercury (Hg) methylation, ND132 has been widely used as a model strain to study the process and to determine the genetic basis of Hg methylation. Originally called ND132 on the basis of an early partial 16S rRNA sequence, the strain has never been formally described. Phylogenetic and physiological traits place this strain within the genus in the recently reclassified phylum (formerly ). ND132 is most closely related to BerOc1 and J2. Analysis of average nucleotide identity (ANI) of whole-genome sequences showed roughly 88 % ANI between BerOc1 and ND132, and 84 % similarity between ND132 and J2. These cut-off scores <95 %, along with a multi-gene phylogenetic analysis of members of the family and differences in physiology indicate that all three strains represent separate species. The Gram-stain-negative cells are vibrio-shaped, motile and not sporulated. ND132 is a salt-tolerant mesophile with optimal growth in the laboratory at 32 °C, 2 % salinity, and pH 7.8. The DNA G+C content of the genomic DNA is 65.2 %. It is an incomplete oxidizer of short chain fatty acids, using lactate, pyruvate and fumarate with sulfate or sulfite as the terminal electron acceptors. ND132 can respire fumarate using pyruvate as an electron donor. The major fatty acids are iso-C, anteiso-C, iso-C, iso-Cω9 and anteiso-C. We propose the classification of strain ND132 (DSM 110689, ATCC TSD-224) as the type strain sp. nov.
PubMed: 33570484
DOI: 10.1099/ijsem.0.004697 -
International Journal of Dentistry 2018This study describes the biofilm formation and the corrosive capacity of sulfate-reducing bacteria (SRB) on the metallic structure of used endodontic files.
AIM
This study describes the biofilm formation and the corrosive capacity of sulfate-reducing bacteria (SRB) on the metallic structure of used endodontic files.
METHODS
Sulfate-reducing bacteria (SRB) ( oral and or environmental) were inoculated into the culture media (Postgate C culture medium or modified Postgate E culture medium). The biocorrosive potential of these bacteria will be an important component of a biopharmaceutical under development called BACCOR. Afterwards, four used endodontic files (UEFs) were separately inoculated into a specific culture media for 445 days at 30°C in an incubator. The four UEFs were placed in a scanning electron microscope (SEM) and analyzed by the energy-dispersive X-ray spectrometry (EDS).
RESULTS
The confocal laser scanning microscopic images indicate the presence of biofilm in the four samples. The SEM and SEM-EDS revealed the presence of rough, irregular structures adhering along the metallic surface of the used endodontic files, suggesting a mature calcified biofilm with a high concentration of Ca, P, C, and S.
CONCLUSION
The formation of SRB biofilms on used endodontic files shows characteristics that may contribute to the biocorrosion of these files, and the results may also provide complementary data for a biopharmaceutical, which is still under development to assist in the removal of fractured endodontic files inside root channels.
PubMed: 29861730
DOI: 10.1155/2018/8303450 -
JCI Insight Oct 2018We hypothesized that the gut microbiota influences survival of murine cardiac allografts through modulation of immunity. Antibiotic pretreated mice received vascularized...
We hypothesized that the gut microbiota influences survival of murine cardiac allografts through modulation of immunity. Antibiotic pretreated mice received vascularized cardiac allografts and fecal microbiota transfer (FMT), along with tacrolimus immunosuppression. FMT source samples were from normal, pregnant (immune suppressed), or spontaneously colitic (inflammation) mice. Bifidobacterium pseudolongum (B. pseudolongum) in pregnant FMT recipients was associated with prolonged allograft survival and lower inflammation and fibrosis, while normal or colitic FMT resulted in inferior survival and worse histology. Transfer of B. pseudolongum alone resulted in reduced inflammation and fibrosis. Stimulation of DC and macrophage lines with B. pseudolongum induced the antiinflammatory cytokine IL-10 and homeostatic chemokine CCL19 but induced lesser amounts of the proinflammatory cytokines TNFα and IL-6. In contrast, LPS and Desulfovibrio desulfuricans (D. desulfuricans), more abundant in colitic FMT, induced a more inflammatory cytokine response. Analysis of mesenteric and peripheral lymph node structure showed that B. pseudolongum gavage resulted in a higher laminin α4/α5 ratio in the lymph node cortical ridge, indicative of a suppressive environment, while D. desulfuricans resulted in a lower laminin α4/α5 ratio, supportive of inflammation. Discrete gut bacterial species alter immunity and may predict graft outcomes through stimulation of myeloid cells and shifts in lymph node structure and permissiveness.
Topics: Allografts; Animals; Anti-Bacterial Agents; Cell Line, Tumor; Colitis; Cytokines; Disease Models, Animal; Fecal Microbiota Transplantation; Female; Gastrointestinal Microbiome; Graft Rejection; Graft Survival; Heart Transplantation; Humans; Immunity, Innate; Immunosuppressive Agents; Lymph Nodes; Mice; Myocardium; Pregnancy; RAW 264.7 Cells; Tacrolimus; Treatment Outcome
PubMed: 30282817
DOI: 10.1172/jci.insight.121045 -
Environmental Science & Technology Oct 2016The disposal of elemental mercury (Hg(0)) wastes in mining and manufacturing areas has caused serious soil and groundwater contamination issues. Under anoxic conditions,...
The disposal of elemental mercury (Hg(0)) wastes in mining and manufacturing areas has caused serious soil and groundwater contamination issues. Under anoxic conditions, certain anaerobic bacteria can oxidize dissolved elemental mercury and convert the oxidized Hg to neurotoxic methylmercury. In this study, we conducted experiments with the Hg-methylating bacterium Desulfovibrio desulfuricans ND132 to elucidate the role of cellular thiols in anaerobic Hg(0) oxidation. The concentrations of cell-surface and intracellular thiols were measured, and specific fractions of D. desulfuricans ND132 were examined for Hg(0) oxidation activity and analyzed with extended X-ray absorption fine structure (EXAFS) spectroscopy. The experimental data indicate that intracellular thiol concentrations are approximately six times higher than those of the cell wall. Cells reacted with a thiol-blocking reagent were severely impaired in Hg(0) oxidation activity. Spheroplasts lacking cell walls rapidly oxidized Hg(0) to Hg(II), while cell wall fragments exhibited low reactivity toward Hg(0). EXAFS analysis of spheroplast samples revealed that multiple different forms of Hg-thiols are produced by the Hg(0) oxidation reaction and that the local coordination environment of the oxidized Hg changes with reaction time. The results of this study indicate that Hg(0) oxidation in D. desulfuricans ND132 is an intracellular process that occurs by reaction with thiol-containing molecules.
PubMed: 27654630
DOI: 10.1021/acs.est.6b03299 -
Applied Microbiology and Biotechnology Sep 2016The potential of sulfate-reducing bacteria (SRB) as biocatalysts for H2 production from formate was recently demonstrated, but the electron transfer pathways involved...
The potential of sulfate-reducing bacteria (SRB) as biocatalysts for H2 production from formate was recently demonstrated, but the electron transfer pathways involved were not described. In the present work, we analyzed the H2 production capacity of five Desulfovibrio strains: Desulfovibrio vulgaris, Desulfovibrio desulfuricans, Desulfovibrio alaskensis, Desulfovibrio fructosivorans, and Desulfovibrio gigas. D. vulgaris showed the highest H2 productivity (865 mL Lmedium (-1)), and D. gigas the lowest one (374 mL Lmedium (-1) of H2). The electron transfer pathways involved in formate-driven H2 production by these two organisms were further investigated through the study of deletion mutants of hydrogenases (Hases) and formate dehydrogenases (Fdhs). In D. vulgaris, the periplasmic FdhAB is the key enzyme for formate oxidation and two pathways are apparently involved in the production of H2 from formate: a direct one only involving periplasmic enzymes and a second one that involves transmembrane electron transfer and may allow energy conservation. In the presence of selenium, the Hys [NiFeSe] Hase is the main periplasmic enzyme responsible for H2 production, and the cytoplasmic Coo Hase is apparently involved in the ability of D. vulgaris to grow by converting formate to H2, in sparging conditions. Contrary to D. vulgaris, H2 production in D. gigas occurs exclusively by the direct periplasmic route and does not involve the single cytoplasmic Hase, Ech. This is the first report of the metabolic pathways involved in formate metabolism in the absence of sulfate in SRB, revealing that the electron transfer pathways are species-specific.
Topics: Biotransformation; Desulfovibrio; Electron Transport; Formates; Gene Deletion; Hydrogen; Metabolic Networks and Pathways
PubMed: 27270746
DOI: 10.1007/s00253-016-7649-7 -
Proteomics Sep 2018Recent studies of microbial mercury (Hg) methylation revealed a key gene pair, hgcAB, which is essential for methylmercury (MeHg) production in the environment. However,...
Recent studies of microbial mercury (Hg) methylation revealed a key gene pair, hgcAB, which is essential for methylmercury (MeHg) production in the environment. However, many aspects of the mechanism and biological processes underlying Hg methylation, as well as any additional physiological functions of the hgcAB genes, remain unknown. Here, quantitative proteomics are used to identify changes in potential functional processes related to hgcAB gene deletion in the Hg-methylating bacterium Desulfovibrio desulfuricans ND132. Global proteomics analyses indicate that the wild type and ΔhgcAB strains are similar with respect to the whole proteome and the identified number of proteins, but differ significantly in the abundance of specific proteins. The authors observe changes in the abundance of proteins related to the glycolysis pathway and one-carbon metabolism, suggesting that the hgcAB gene pair is linked to carbon metabolism. Unexpectedly, the authors find that the deletion of hgcAB significantly impacts a range of metal transport proteins, specifically membrane efflux pumps such as those associated with heavy metal copper (Cu) export, leading to decreased Cu uptake in the ΔhgcAB mutant. This observation indicates possible linkages between this set of proteins and metal homeostasis in the cell. However, hgcAB gene expression is not induced by Hg, as evidenced by similarly low abundance of HgcA and HgcB proteins in the absence or presence of Hg (500 nm). Taken together, these results suggest an apparent link between HgcAB, one-carbon metabolism, and metal homeostasis, thereby providing insights for further exploration of biochemical mechanisms and biological functions of microbial Hg methylation.
Topics: Bacterial Proteins; Biological Phenomena; Desulfovibrio desulfuricans; Gene Deletion; Metabolic Networks and Pathways; Methylation; Methylmercury Compounds; Proteome
PubMed: 30009483
DOI: 10.1002/pmic.201700479 -
Microbial Biotechnology Sep 2021Desulfovibrio desulfuricans reduces Pd(II) to Pd(0)-nanoparticles (Pd-NPs) which are catalytically active in 2-pentyne hydrogenation. To make Pd-NPs, resting cells are...
Desulfovibrio desulfuricans reduces Pd(II) to Pd(0)-nanoparticles (Pd-NPs) which are catalytically active in 2-pentyne hydrogenation. To make Pd-NPs, resting cells are challenged with Pd(II) ions (uptake), followed by addition of electron donor to promote bioreduction of cell-bound Pd(II) to Pd(0) (bio-Pd). Application of radiofrequency (RF) radiation to prepared 5 wt% bio-Pd catalyst (60 W power, 60 min) increased the hydrogenation rate by 70% with no adverse impact on selectivity to cis-2-pentene. Such treatment of a 5 wt% Pd/carbon commercial catalyst did not affect the conversion rate but reduced the selectivity. Lower-dose RF radiation (2-8 W power, 20 min) was applied to the bacteria at various stages before and during synthesis of the bio-scaffolded Pd-NPs. The reaction rate (μ mol 2-pentyne converted s ) was increased by ~threefold by treatment during bacterial catalyst synthesis. Application of RF radiation (2 or 4 W power) to resting cells prior to Pd(II) exposure affected the catalyst made subsequently, increasing the reaction rate by 50% as compared to untreated cells, while nearly doubling selectivity for cis 2-pentene. The results are discussed with respect to published and related work which shows altered dispersion of the Pd-NPs made following or during RF exposure.
Topics: Alkenes; Biological Transport; Desulfovibrio desulfuricans; Hydrogenation; Magnetic Fields
PubMed: 34216193
DOI: 10.1111/1751-7915.13878