scholarly journals Sustained dechlorination of vinyl chloride to ethene inDehalococcoides-enriched cultures grown without addition of exogenous vitamins and at low pH

2019 ◽  
Author(s):  
Luz A. Puentes Jácome ◽  
Po-Hsiang Wang ◽  
Olivia Molenda ◽  
Yi Xuan (Jine-Jine) Li ◽  
M. Ahsanul Islam ◽  
...  
Keyword(s):  
Vinyl Chloride ◽  
Low Ph ◽  
Mineral Medium ◽  
Ex Situ ◽  
Microbial Consortia ◽  
Neutral Ph ◽  
Cell Extracts ◽  
Enriched Cultures ◽  
Lower Ligand ◽  
Groundwater Pollutant

ABSTRACTTrichloroethene (TCE) is a ubiquitous groundwater pollutant. Successful TCE bioremediation has been demonstrated at field sites using specialized microbial consortia harboring TCE-respiringDehaloccocoideswhose growth is cobalamin (vitamin B12)-dependent. Bioaugmentation cultures grown ex situ with ample exogenous vitamins in the medium and at neutral pH may become vitamin-limited or inhibited by acidic pH once injected into field sites, resulting in incomplete TCE dechlorination and accumulation of more toxic vinyl chloride (VC). Here, we report growth of theDehalococcoides-containing bioaugmentation culture KB-1 in a TCE-amended mineral medium devoid of vitamins and in a VC-amended mineral medium at low pH (6.0 and 5.5). In cultures grown without exogenous vitamins or cobalamin,Acetobacterium, which can synthesize 5,6-dimethylbenzimidazole (DMB), the lower ligand of cobalamin, andSporomusaare the dominant acetogens. At neutral pH, a growingAcetobacteriumpopulation supports complete TCE dechlorination byDehalococcoidesat millimolar levels with a substantial increase in the amount of measured cobalamin (~20-fold). Sustained dechlorination of VC to ethene was achieved at a pH as low as 5.5, yet at low pHAcetobacteriumis less abundant, potentially affecting the production of DMB and/or cobalamin. However, dechlorination activity at very low pH (< 5.0) was not stimulated by DMB supplementation, but was restored by raising pH to neutral. Assays in cell extracts revealed that vinyl chloride reductase (VcrA) activity declines significantly below pH 6.0 and is undetectable below pH 5.0. This study highlights the roles of and interplay between vitamin-producing populations and pH in microbial dechlorinating communities, and their importance for successful chlorinated ethenes bioremediation at field sites.

scholarly journals Association of Missense Mutations in Epoxyalkane Coenzyme M Transferase with Adaptation of Mycobacterium sp. Strain JS623 to Growth on Vinyl Chloride

2010 ◽  
Vol 76 (11) ◽  
pp. 3413-3419 ◽  
Author(s):  
Yang Oh Jin ◽  
Samantha Cheung ◽  
Nicholas V. Coleman ◽  
Timothy E. Mattes
Keyword(s):  
Vinyl Chloride ◽  
Mycobacterium Smegmatis ◽  
Missense Mutations ◽  
Wild Type ◽  
Coenzyme M ◽  
Genetic Changes ◽  
Cell Extracts ◽  
Chlorinated Solvent ◽  
Groundwater Pollutant

ABSTRACT Vinyl chloride (VC) is a toxic groundwater pollutant associated with plastic manufacture and chlorinated solvent use. Aerobic bacteria that grow on VC as a carbon and energy source can evolve in the laboratory from bacteria that grow on ethene, but the genetic changes involved are unknown. We investigated VC adaptation in two variants (JS623-E and JS623-T) of the ethene-oxidizing Mycobacterium strain JS623. Missense mutations in the EtnE gene developed at two positions (W243 and R257) in cultures exposed to VC but not in cultures maintained on ethene. Epoxyalkane-coenzyme M transferase (EaCoMT) activities in cell extracts of JS623-E and JS623-T (150 and 645 nmol/min/mg protein, respectively) were higher than that of wild-type JS623 (74 nmol/min/mg protein), and in both variant cultures epoxyethane no longer accumulated during growth on ethene. The heterologous expression of two variant etnE alleles (W243G [etnE1] and R257L [etnE2]) from strain JS623 in Mycobacterium smegmatis showed that they had 42 to 59% higher activities than the wild type. Recombinant JS623 cultures containing mutant EtnE genes cloned in the vector pMV261 adapted to growth on VC more rapidly than the wild-type JS623 strain, with incubation times of 60 days (wild type), 1 day (pMVetnE1), and 35 days (pMVetnE2). The JS623(pMVetnE) culture did not adapt to VC after more than 60 days of incubation. Adaptation to VC in strain JS623 is consistently associated with two particular missense mutations in the etnE gene that lead to higher EaCoMT activity. This is the first report to pinpoint a genetic change associated with the transition from cometabolic to growth-linked VC oxidation in bacteria.

scholarly journals Sustained Dechlorination of Vinyl Chloride to Ethene in Dehalococcoides-Enriched Cultures Grown without Addition of Exogenous Vitamins and at Low pH

2019 ◽  
Vol 53 (19) ◽  
pp. 11364-11374 ◽  
Author(s):  
Luz A. Puentes Jácome ◽  
Po-Hsiang Wang ◽  
Olivia Molenda ◽  
Yi Xuan (Jine-Jine) Li ◽  
M. Ahsanul Islam ◽  
...  
Keyword(s):  
Vinyl Chloride ◽  
Low Ph ◽  
Enriched Cultures

scholarly journals Diphtheria toxin entry into cells is facilitated by low pH.

1980 ◽  
Vol 87 (3) ◽  
pp. 828-832 ◽  
Author(s):  
K Sandvig ◽  
S Olsnes
Keyword(s):  
Protein Synthesis ◽  
Toxic Effect ◽  
Diphtheria Toxin ◽  
Surface Membrane ◽  
Low Ph ◽  
Toxin A ◽  
Neutral Ph ◽  
Diphtheria Toxin A ◽  
Adsorptive Endocytosis

At neutral pH, NH4Cl and chloroquine protected cells against diphtheria toxin. A brief exposure of the cells to low pH (4.5-5.5) at 37 degrees completely abolished this protection. When, to cells preincubated with diphtheria toxin and NH4Cl, neutralizing amounts of anti-diphtheria toxin were added before the pH was lowered, the toxic effect was considerably reduced, but it was not completely abolished. A much stronger toxic effect was seen when antibodies were added immediately after incubation at low pH. Upon a short incubation with diphtheria toxin at low pH, the rate of protein synthesis in the cells decreased much faster than when the normal pH was maintained. The data suggest that, at low pH, diphtheria toxin (or its A fragment) penetrates directly through the surface membrane of the cell. The possibility is discussed that, when the medium has a neutral pH, the entry of diphtheria toxin involves adsorptive endocytosis and reduction of the pH in the vesicles possibly by fusion with lysosomes. Low pH did not facilitate the entry of the closely related toxins abrin, ricin, and modeccin.

scholarly journals Low-pH-Dependent Fusion of Sindbis Virus with Receptor-Free Cholesterol- and Sphingolipid-Containing Liposomes

1999 ◽  
Vol 73 (10) ◽  
pp. 8476-8484 ◽  
Author(s):  
Jolanda M. Smit ◽  
Robert Bittman ◽  
Jan Wilschut
Keyword(s):  
Sindbis Virus ◽  
Core Protein ◽  
Fusion Reaction ◽  
Low Ph ◽  
Viral Envelope ◽  
Cell Entry ◽  
Receptor Interaction ◽  
Neutral Ph ◽  
Virus Fusion ◽  
Entry Mechanism

ABSTRACT There is controversy as to whether the cell entry mechanism of Sindbis virus (SIN) involves direct fusion of the viral envelope with the plasma membrane at neutral pH or uptake by receptor-mediated endocytosis and subsequent low-pH-induced fusion from within acidic endosomes. Here, we studied the membrane fusion activity of SIN in a liposomal model system. Fusion was followed fluorometrically by monitoring the dilution of pyrene-labeled lipids from biosynthetically labeled virus into unlabeled liposomes or from labeled liposomes into unlabeled virus. Fusion was also assessed on the basis of degradation of the viral core protein by trypsin encapsulated in the liposomes. SIN fused efficiently with receptor-free liposomes, consisting of phospholipids and cholesterol, indicating that receptor interaction is not a mechanistic requirement for fusion of the virus. Fusion was optimal at pH 5.0, with a threshold at pH 6.0, and undetectable at neutral pH, supporting a cell entry mechanism of SIN involving fusion from within acidic endosomes. Under optimal conditions, 60 to 85% of the virus fused, depending on the assay used, corresponding to all of the virus bound to the liposomes as assessed in a direct binding assay. Preincubation of the virus alone at pH 5.0 resulted in a rapid loss of fusion capacity. Fusion of SIN required the presence of both cholesterol and sphingolipid in the target liposomes, cholesterol being primarily involved in low-pH-induced virus-liposome binding and the sphingolipid catalyzing the fusion process itself. Under low-pH conditions, the E2/E1 heterodimeric envelope glycoprotein of the virus dissociated, with formation of a trypsin-resistant E1 homotrimer, which kinetically preceded the fusion reaction, thus suggesting that the E1 trimer represents the fusion-active conformation of the viral spike.

scholarly journals Ample Arsenite Bio-Oxidation Activity in Bangladesh Drinking Water Wells: A Bonanza for Bioremediation?

2019 ◽  
Vol 7 (8) ◽  
pp. 246
Author(s):  
Zahid Hassan ◽  
Munawar Sultana ◽  
Sirajul I. Khan ◽  
Martin Braster ◽  
Wilfred F.M. Röling ◽  
...  
Keyword(s):  
Drinking Water ◽  
Ex Situ ◽  
Rrna Gene ◽  
Microbial Activities ◽  
16S Rrna Gene Sequences ◽  
Previous Survey ◽  
Oxidation Activity ◽  
Water Wells ◽  
Enriched Cultures ◽  
Biological Solutions

Millions of people worldwide are at risk of arsenic poisoning from their drinking water. In Bangladesh the problem extends to rural drinking water wells, where non-biological solutions are not feasible. In serial enrichment cultures of water from various Bangladesh drinking water wells, we found transfer-persistent arsenite oxidation activity under four conditions (aerobic/anaerobic; heterotrophic/autotrophic). This suggests that biological decontamination may help ameliorate the problem. The enriched microbial communities were phylogenetically at least as diverse as the unenriched communities: they contained a bonanza of 16S rRNA gene sequences. These related to Hydrogenophaga, Acinetobacter, Dechloromonas, Comamonas, and Rhizobium/Agrobacterium species. In addition, the enriched microbiomes contained genes highly similar to the arsenite oxidase (aioA) gene of chemolithoautotrophic (e.g., Paracoccus sp. SY) and heterotrophic arsenite-oxidizing strains. The enriched cultures also contained aioA phylotypes not detected in the previous survey of uncultivated samples from the same wells. Anaerobic enrichments disclosed a wider diversity of arsenite oxidizing aioA phylotypes than did aerobic enrichments. The cultivatable chemolithoautotrophic and heterotrophic arsenite oxidizers are of great interest for future in or ex-situ arsenic bioremediation technologies for the detoxification of drinking water by oxidizing arsenite to arsenate that should then precipitates with iron oxides. The microbial activities required for such a technology seem present, amplifiable, diverse and hence robust.

Two-stage biofiltration of sulfides and VOCs from wastewater treatment plants

2000 ◽  
Vol 42 (5-6) ◽  
pp. 411-418 ◽  
Author(s):  
J.S. Devinny ◽  
D.E. Chitwood
Keyword(s):  
Organic Compounds ◽  
Wastewater Treatment Plants ◽  
Pilot Scale ◽  
Low Ph ◽  
Single Stage ◽  
Two Stage ◽  
Neutral Ph ◽  
Support Medium ◽  
Waste Air ◽  
Air Streams

Hydrogen sulfide and volatile organic compounds are often found together in waste air streams. This combination is difficult to treat by biofiltration because oxidation of the sulfide produces acid, reducing the pH in the biofilter. Rapid declines in pH can inhibit treatment of organic compounds. A two-stage biofilter, with the first stage operated at low pH and an inorganic support medium, and the second operated at neutral pH with an organic support can eliminate the problem. A pilot-scale facility was operated on this principle. Comparisons were made among two-stage treatment, single-stage low pH treatment, and single-stage uncontrolled treatment to determine which of the strategies was most effective. In two-stage treatment the first stage did provide protection for the second, allowing it to operate at neutral pH. Single-stage low pH treatment was effective at removing sulfide and many organic compounds, and may be sufficient for many applications.

Evidence for Less Irritation to the Peritoneal Membrane in Rats Dialyzed with Solutions Low in Glucose Degradation Products

2004 ◽  
Vol 24 (1) ◽  
pp. 48-57 ◽  
Author(s):  
Katarzyna Wieczorowska–Tobis ◽  
Renata Brelinska ◽  
Janusz Witowski ◽  
Jutta Passlick–Deetjen ◽  
Thomas P. Schaub ◽  
...  
Keyword(s):  
Structural Integrity ◽  
Degradation Products ◽  
Low Ph ◽  
Vascular Density ◽  
Peritoneal Membrane ◽  
Single Chamber ◽  
Neutral Ph ◽  
Glucose Degradation Products ◽  
Chronic Infusion ◽  
New Generation

Background Acidic pH and the presence of glucose degradation products (GDP) are believed to compromise the biocompatibility of peritoneal dialysis fluids (PDF). The present study examines the effects of long-term exposure to GDP and low pH by comparing conventional PDF and a new, neutral pH, low GDP solution. Methods All experiments were performed using a chronic infusion model of dialysis in nonuremic rats. The animals were treated for 6 weeks with 2 daily injections of 4.25% glucose-containing PDF. The following PDF were tested: CAPD3 (single-chamber bag, low pH, high GDP), CAPD3 pH 7.4 (single-chamber bag, neutral pH, high GDP), CAPD3-Balance (double-chamber bag, neutral pH, low GDP). All test solutions were obtained from Fresenius Medical Care, Bad Homburg, Germany. Results After 6 weeks of exposure, peritoneal permeability to water, urea, creatinine, glucose, and sodium, assessed by peritoneal equilibration test, was similar in all groups. However, compared to other PDF, dialysis with CAPD3-Balance was associated with reduced concentrations of protein and hyaluronan in the dialysate, decreased peritoneal eosinophilia, and reduced dialysate levels of chemokines CCL2/MCP-1 and CCL5/RANTES. Morphologic changes in the peritoneal membrane of CAPD3-Balance-treated animals were much less pronounced and included reduced vascular density, preservation of the mesothelial monolayer and intercellular junction, and no reduplication of the submesothelial basement membrane. Conclusions A new generation of PDF with physiologic pH and low GDP level produce less irritation to the peritoneal membrane and better preserve its structural integrity. This effect seems to be related predominantly to minimized GDP concentrations.

scholarly journals The Avian Retrovirus Avian Sarcoma/Leukosis Virus Subtype A Reaches the Lipid Mixing Stage of Fusion at Neutral pH

2003 ◽  
Vol 77 (5) ◽  
pp. 3058-3066 ◽  
Author(s):  
Laurie J. Earp ◽  
Sue E. Delos ◽  
Robert C. Netter ◽  
Paul Bates ◽  
Judith M. White
Keyword(s):  
Cell Fusion ◽  
Receptor Binding ◽  
Low Ph ◽  
Target Cells ◽  
Dependent Manner ◽  
Neutral Ph ◽  
Subtype A ◽  
Avian Sarcoma ◽  
Virus Subtype ◽  
Cell Cell

ABSTRACT We previously showed that the envelope glycoprotein (EnvA) of avian sarcoma/leukosis virus subtype A (ASLV-A) binds to liposomes at neutral pH following incubation with its receptor, Tva, at ≥22°C. We also provided evidence that ASLV-C fuses with cells at neutral pH. These findings suggested that receptor binding at neutral pH and ≥22°C is sufficient to activate Env for fusion. A recent study suggested that two steps are necessary to activate avian retroviral Envs: receptor binding at neutral pH, followed by exposure to low pH (W. Mothes et al., Cell 103:679-689, 2000). Therefore, we evaluated the requirements for intact ASLV-A particles to bind to target bilayers and fuse with cells. We found that ASLV-A particles bind stably to liposomes in a receptor- and temperature-dependent manner at neutral pH. Using ASLV-A particles biosynthetically labeled with pyrene, we found that ASLV-A mixes its lipid envelope with cells within 5 to 10 min at 37°C. Lipid mixing was neither inhibited nor enhanced by incubation at low pH. Lipid mixing of ASLV-A was inhibited by a peptide designed to prevent six-helix bundle formation in EnvA; the same peptide inhibits virus infection and EnvA-mediated cell-cell fusion (at both neutral and low pHs). Bafilomycin and dominant-negative dynamin inhibited lipid mixing of Sindbis virus (which requires low pH for fusion), but not of ASLV-A, with host cells. Finally, we found that, although EnvA-induced cell-cell fusion is enhanced at low pH, a mutant EnvA that is severely compromised in its ability to support infection still induced massive syncytia at low pH. Our results indicate that receptor binding at neutral pH is sufficient to activate EnvA, such that ASLV-A particles bind hydrophobically to and merge their membranes with target cells. Possible roles for low pH at subsequent stages of viral entry are discussed.

scholarly journals The Transition from a Neutral-pH Double Helix to a Low-pH Triple Helix Induces a Conformational Switch in the CCCG Tetraloop Closing a Watson-Crick Stem

1996 ◽  
Vol 263 (5) ◽  
pp. 715-729 ◽  
Author(s):  
Maria J.P. van Dongen ◽  
Sybren S. Wijmenga ◽  
Gijs A. van der Marel ◽  
Jacques H. van Boom ◽  
Cornelis W. Hilbers
Keyword(s):  
Triple Helix ◽  
Double Helix ◽  
Low Ph ◽  
Conformational Switch ◽  
Neutral Ph

scholarly journals An Acid-activated Nucleobase Transporter from Leishmania major

2009 ◽  
Vol 284 (24) ◽  
pp. 16164-16169 ◽  
Author(s):  
Diana Ortiz ◽  
Marco A. Sanchez ◽  
Hans P. Koch ◽  
H. Peter Larsson ◽  
Scott M. Landfear
Keyword(s):  
Leishmania Major ◽  
De Novo ◽  
Low Ph ◽  
Acidic Ph ◽  
Physiological Conditions ◽  
Neutral Ph ◽  
Amastigote Stage ◽  
Electrode Voltage ◽  
Ph Conditions ◽  
Micromolar Range

Parasitic protozoa are unable to synthesize purines de novo and must import preformed purine nucleobases or nucleosides from their hosts. Leishmania major expresses two purine nucleobase transporters, LmaNT3 and LmaNT4. Previous studies revealed that at neutral pH, LmaNT3 is a broad specificity, high affinity nucleobase transporter, whereas LmaNT4 mediates the uptake of only adenine. Because LmaNT4 is required for optimal viability of the amastigote stage of the parasite that lives within acidified phagolysomal vesicles of mammalian macrophages, the function of this permease was examined under acidic pH conditions. At acidic pH, LmaNT4 acquires the ability to transport adenine, hypoxanthine, guanine, and xanthine with Km values in the micromolar range, indicating that this transporter is activated at low pH. Thus, LmaNT4 is an acid-activated purine nucleobase transporter that functions optimally under the physiological conditions the parasite is exposed to in the macrophage phagolysosome. In contrast, LmaNT3 functions optimally at neutral pH. Two-electrode voltage clamp experiments performed on LmaNT3 and LmaNT4 expressed in Xenopus oocytes revealed substrate-induced inward directed currents at acidic pH, and application of substrates induced acidification of the oocyte cytosol. These observations imply that LmaNT3 and LmaNT4 are nucleobase/proton symporters.

Sign in / Sign up

Export Citation Format

Share Document