Attenuation effects of ZVI/PDS pretreatment on propagation of antibiotic resistance genes in bioreactors: Driven by antibiotic residues and sulfate assimilation.

Sulfate radical-based advanced oxidation processes (AOPs) combined biological system was a promising technology for treating antibiotic wastewater. However, how pretreatment influence antibiotic resistance genes (ARGs) propagation remains largely elusive, especially the produced by-products (antibiotic residues and sulfate) are often ignored. Herein, we investigated the effects of zero valent iron/persulfate pretreatment on ARGs in bioreactors treating sulfadiazine wastewater. Results showed absolute and relative abundance of ARGs reduced by 59.8%- 81.9% and 9.1%- 52.9% after pretreatments. The effect of 90-min pretreatment was better than that of the 30-min. The ARGs reduction was due to decreased antibiotic residues and stimulated sulfate assimilation. Reduced antibiotic residues was a major factor in ARGs attenuation, which could suppress oxidative stress, inhibit mobile genetic elements emergence and resistant strains proliferation. The presence of sulfate in influent supplemented microbial sulfur sources and facilitated the in-situ synthesis of antioxidant cysteine through sulfate assimilation, which drove ARGs attenuation by alleviating oxidative stress. This is the first detailed analysis about the regulatory mechanism of how sulfate radical-based AOPs mediate in ARGs attenuation, which is expected to provide theoretical basis for solving concerns about by-products and developing practical methods to hinder ARGs propagation.

Reduction and functionalization of graphene oxide with L-cysteine: Synthesis, characterization and biocompatibility.

This article presents data on the synthesis, identification, computer simulation and biocompatibility of graphene oxide (GO) functionalized with L-cysteine (GFC). It was determined that GO reacts with L-cysteine in two different ways: in an alkaline medium, L-cysteine reduces functional groups on the surface and at the boundaries of GO; with heating and the use of thionyl chloride, L-cysteine covalently attaches to GO through carboxylic groups only at the boundaries. The identification of GO, reduced graphene oxide and GFC was performed using various physicochemical methods, including infrared spectroscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis, scanning electron microscopy and high-resolution transmission electron microscopy. Biocompatibility experiments included erythrocyte hemolysis, platelet aggregation, photodynamic and antiradical activity, binding to human serum albumin, and geno- and cytotoxicity studies. Applying density functional theory and molecular dynamics allowed us to obtain the structural and dynamic characteristics of a GFC-water binary system.

A naphthalimide derivative can release COS and form H2S in a light-controlled manner and protect cells against ROS with real-time monitoring ability.

As an important gasotransmitter, hydrogen sulfide having multiple biological roles cannot be easily probed in cells. In this study, a light controllable H2S donor, Nap-Sul-ONB, derived from naphthalimide was developed. Under the irradiation of 365 nm light, a readily controlled stimulus, the donor could release COS to form H2S and exhibit turn on fluorescence to indicate the release of payload and its cellular location. Besides, the ROS scavenging ability and cell protective effect of Nap-Sul-ONB against endogenous and exogenous ROS were studied. The results showed that upon 365 nm light irradiation, Nap-Sul-ONB could reduce the cellular ROS level and increase the survival rate of PMA-treated cells.

Investigations into the carbonic anhydrase inhibition of COS-releasing donor core motifs.

Carbonyl sulfide (COS) releasing scaffolds are gaining popularity as hydrogen sulfide (H2S) donors through exploitation of the carbonic anhydrase (CA)-mediated hydrolysis of COS to H2S. The majority of compounds in this emerging class of donors undergo triggerable decomposition (often referred to as self-immolation) to release COS, and a handful of different COS-releasing structures have been reported. One benefit of this donation strategy is that numerous caged COS-containing core motifs are possible and are poised for development into self-immolative COS/H2S donors. Because the intermediate release of COS en route to H2S donation requires CA, it is important that the COS donor motifs do not inhibit CA directly. In this work, we investigate the cytotoxicity and CA inhibition properties of different caged COS donor cores, as well as caged CO2 and CS2 motifs and non-self-immolative control compounds. None of the compounds investigated exhibited significant cytotoxicity or enhanced cell proliferation at concentrations up to 100 µM in A549 cells, but we identified four core structures that function as CA inhibitors, thus providing a roadmap for the future development of self-immolative COS/H2S donor motifs.

Activity-Based Profiling Reveals a Regulatory Link between Oxidative Stress and Protein Arginine Phosphorylation.

Protein arginine phosphorylation is a recently discovered modification that affects multiple cellular pathways in Gram-positive bacteria. In particular, the phosphorylation of arginine residues by McsB is critical for regulating the cellular stress response. Given that the highly efficient protein arginine phosphatase YwlE prevents arginine phosphorylation under non-stress conditions, we hypothesized that this enzyme negatively regulates arginine phosphorylation and acts as a sensor of cell stress. To evaluate this hypothesis, we developed the first suite of highly potent and specific SO3-amidine-based YwlE inhibitors. With these protein arginine phosphatase-specific probes, we demonstrated that YwlE activity is suppressed by oxidative stress, which consequently increases arginine phosphorylation, thereby inducing the expression of stress-response genes, which is critical for bacterial virulence. Overall, we predict that these novel chemical tools will be widely used to study the regulation of protein arginine phosphorylation in multiple organisms.

Study on biotribological properties of UHMWPE grafted with MPDSAH.

In order to prolong the service life of artificial joints, a zwitterion monomer of MPDSAH ((3-(methacryloylamino)propyl)dimethyl (3-sulfopropyl)ammonium hydroxide) was grafted onto ultra-high molecular weight polyethylene (UHMWPE) powders to construct a brush-like structure by UV irradiation, and then the grafted UHMWPE powders were hot pressed as the bulk materials. The wettability of bulk materials surface with different monomer concentrations was analyzed. The tribological properties of modified UHMWPE bulk materials were investigated under distilled water and saline by sliding against stainless steel ball. The measurement of Fourier-transform infrared (FT-IR) spectroscopy indicates that MPDSAH is successfully grafted onto the surface of UHMWPE powders by UV irradiation. The contact angles of modified UHMWPE are decreased and the surface wettability is effectively improved. The friction coefficient of the modified sample is lower than that of untreated UHMWPE in aqueous lubricants during a long-term friction. With the increase of monomer concentration, the wear rate of grafted UHMWPE decreases gradually in distilled water. The grafting hydrophilic macromolecule polymer is helpful to form a lubricating film of water, which leads to the improvement of the lubricity of UHMWPE.

Effects of carbonyl sulfide and carbonic anhydrase on stomatal conductance.

The potential use of carbonyl sulfide (COS) as tracer of CO(2) flux into the land biosphere stimulated research on COS interactions with leaves during gas exchange. We carried out leaf gas-exchange measurements of COS and CO(2) in 22 plant species representing deciduous and evergreen trees, grasses, and shrubs, under a range of light intensities, using mid-infrared laser spectroscopy. A narrow range in the normalized ratio of the net uptake rates of COS (A(s)) and CO(2) (A(c)), leaf relative uptake (A(s)/A(c) × [CO(2)]/[COS]), was observed, with a mean value of 1.61 ± 0.26, which is advantageous to the use of COS in photosynthesis research. Notably, increasing COS concentrations between 250 and 2,800 pmol mol(-1) (enveloping atmospheric levels) enhanced stomatal conductance (g(s)) to a variable extent in most plants examined (up to a normalized enhancement factor [ f(e) = (g(s-max) - g(s-min))/g(s-min)] of 1). This enhancement was completely abolished in carbonic anhydrase (CA)-deficient antisense lines of both C3 and C4 plants. We suggest that the stomatal response is mediated by CA and may involve hydrogen sulfide formed in the reaction of COS and water with CA. In all species examined, the uptake rates of COS and CO(2) were highly correlated, but there was no relationship between the sensitivity of stomata to COS and the rate of COS uptake (or, by inference, hydrogen sulfide production). The basis for the observed stomatal sensitivity and its variations is still to be determined.

Differential expression profiles of Alternaria alternate genes in response to carbonyl sulfide fumigation.

Carbonyl sulfide (COS) is a new fumigant used in phytosanitary treatments. It was developed as a potential alternative to methyl bromide, which is being phased out because of its ozone-depletion properties. To understand the molecular and cellular mechanisms occurring in fungal pathogens in response to COS fumigation, we cloned 510 cDNA fragments of Alternaria alternata (Fr.) Keissler genes that are differentially expressed; these genes were cloned using suppression subtractive hybridization. Changes in the levels of transcripts of 79 fragments were confirmed by microarray analysis and qRT-PCR. Further homology search revealed that they are highly homologous to 41 genes of other fungi, which were related to general metabolism, growth and division, defense, cellular transport, and signal transduction. These results provide an overview of differential expression profiles of A. alternata genes following COS treatment and some new clues about the mechanism of COS fungitoxicity.

[The effect of various iron hydroxide concentrations on the anaerobic fermentation of sulfate-containing model sewage].

The addition of iron hydroxide and iron-reducing bacteria into a fermenter for anaerobic processing of sulfate-containing sewage was shown to decrease sulfate reduction and sulfide concentration, while increasing the total organic carbon (TOC) and methane production. The effect of iron (III) in sulfate-containing sewage depended on its dose, which can be expressed as molar ratio Fe(III)/SO4(2-). Sulfide concentration increased monotonically, reaching 91 mg/l and 45 mg/l after 15 days of processing at Fe(III)/SO4(2-) ratios of 0.06 and 0.5, respectively. However, soluble sulfide production was not observed at ratios equaling 1 and 2. At ratios of 0.06, 0.5, 1, and 2, the maximum rates of TOC removal were 0.75, 1.15, 1.39, and 1.55 g TOC/g of organic matter (OM) per 1 h. Methane production rates were 0.039, 0.047, 0.064, and 0.069 mg/g OM per 1 h, with the mean relative amounts of methane in the biogas being equal to 25, 41, 55, and 62%, respectively. These data can be applied to the development of new methods of anaerobic purification of sulfate-containing sewage.

Desiccation responses and survival of Sinorhizobium meliloti USDA 1021 in relation to growth phase, temperature, chloride and sulfate availability.

AIMS: To identify physical and physiological conditions that affect the survival of Sinorhizobium meliloti USDA 1021 during desiccation. METHODS AND RESULTS: An assay was developed to study desiccation response of S. meliloti USDA 1021 over a range of environmental conditions. We determined the survival during desiccation in relation to (i) matrices and media, (ii) growth phase, (iii) temperature, and (iv) chloride and sulfate availability. CONCLUSIONS: This study indicates that survival of S. meliloti USDA 1021 during desiccation is enhanced: (i) when cells were dried in the stationary phase, (ii) with increasing drying temperature at an optimum of 37 degrees C, and (iii) during an increase of chloride and sulfate, but not sodium or potassium availability. In addition, we resolved that the best matrix to test survival was nitrocellulose filters. SIGNIFICANCE AND IMPACT OF THE STUDY: The identification of physical and physiological factors that determine the survival during desiccation of S. meliloti USDA 1021 may aid in (i) the strategic development of improved seed inocula, (ii) the isolation, and (iii) the development of rhizobial strains with improved ability to survive desiccation. Furthermore, this work may provide insights into the survival of rhizobia under drought conditions.

Pyrimidinethione nucleosides and their deaza analogues.

The methods of preparation, structure, chemical properties and synthetic potentiality of pyrimidinethione nucleosides and their deaza analogues are reported.

Methods to enhance tolerances of Chlorella KR-1 to toxic compounds in flue gas.

Possible methods to minimize the toxic effects of SOx and NOx on the growth of a highly CO2 tolerant and fast-growing microalga, Chlorella sp. KR-1, were investigated. Maintaining the pH of the culturing media at an adequate value was quite important to enhancing the tolerances of the microalgae to SOx and NOx. Controlling the pH by adding an alkaline solution, using a low flow rate of gas fed to the culture, and using a high concentration of inoculating cells were effective methods to maintaining the proper pH of the culture. Controlling the pH was the most effective method but could be applied only for some specific microalgae.

Stimulatory effects of sulfur and nitrogen oxides on carcinogen activation in human polymorphonuclear leukocytes.

The occurrence of inflammatory processes and of cancer in the human respiratory tract is intimately associated. One of the major factors in this is probably the recruitment of and stimulated activity of polymorphonuclear leukocytes (PML) in conjunction with the ability of these cells to convert various carcinogens to their ultimate active metabolites. In this study, we demonstrate that nitrite and sulfite, the major dissolution products of the environmental pollutants nitrogen dioxide and sulfur dioxide in water enhance the metabolic activation of trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (BP-7,8-dihydrodiol), the proximal carcinogen of benzo[a]pyrene, to trans-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) and tetraols, the corresponding hydrolysis products, in human PML prestimulated with 12-O-tetradecanoylphorbol-13-acetate. Nitrite was more efficient than sulfite in stimulating the formation of reactive intermediates of BP-7,8-dihydrodiol in PML that covalently bind to extracellular DNA and, in particular, to intracellular proteins. The mechanism by which sulfite stimulates the metabolism of BP-7,8-dihydrodiol most probably involves the intermediate formation of a sulfur trioxide radical anion (SO3.-) the subsequent formation of the corresponding sulfur peroxyl radical anion (.OOSO3-) in the presence of oxygen. The mechanism underlying the stimulatory action of nitrite is less clear but the major pathway seems to involve myeloperoxidase. These results offer an explanation for the increased incidence of lung cancer in cigarette smokers living in urban areas. The major glutathione transferase (GST) isoenzyme in human PML is GST P1-1, a Pi-class form. The GST activity of PML was found to be inversely correlated with the extent of binding of BP-7,8-dihydrodiol products to exogenous DNA. These results suggest that individuals exhibiting high GST-activity in the PML may be better protected against the type of carcinogenic dealt with in this study.

Age related effects of lectins on GAG metabolism in cultured embryonic fibroblasts.

Lectins (WGA, SBA or PNA) were administered to 7 and 14 days chick embryo fibroblasts to evaluate their ability to influence GAG cellular and extracellular accumulation. HA and sulphated GAG were differently affected by lectins. WGA addition to culture medium enhanced HA and sulphated GAG in the two examined compartments. SBA and PNA increased sulphated GAG only in the cellular pool with a consequent reduction of secreted GAG. As far as HA is concerned, SBA and PNA promoted its accumulation in the extracellular compartment. NH4Cl administration indicated a decline of GAG degradation in the course of development in presence of lectins. Generally the effect of lectins was greater in the youngest stage: showing that lectins were able to bind 7 and 14 days-old fibroblasts differently.

The effect of HCO3- on anion-stimulated ATPase from rat parotid granules.

ATPase from isolated secretory granules was stimulated in a concentration-dependent manner by HCO3- above 0.9 mM. Maximal stimulation was found at about 16 mM HCO3- and was about half of that with sulphite (SO3(2-)). The activation site(s) appeared to be similar to at least one class of SO3(2-) sites, HCO3(-)-stimulate ATPase was inhibited by SITS. Furthermore, maximal stimulation with SO3(2-) was not enhanced with HCO3-. At low Mg2+ concentrations, Ca2+ stimulated granule ATPase. At higher concentrations of Mg2+ (0.5 mM and above), Ca2+ at 0.1 mM or less had little effect on HCO3(-)-ATPase, and Ca2+ at 4 mM inhibited HCO3(-)-ATPase. At concentrations of Ca2+ above 0.44 mM, the enzyme was partially stimulated in the absence of Mg2+ and presence of HCO3-. Mitochondrial contamination did not account for the presence of ATPase in the isolated granule fraction. The granule ATPase may be regulated by HCO3- and calcium and this could be related to changes in the granule environment during exocytosis.

Growth of microalgae in high CO2 gas and effects of SOX and NOX.

Growth and lipid production of microalgae were investigated, with attention to the feasibility of making use of flue gas CO2 as a carbon source. The effect of a high CO2 level in artificial seawater differed from strain to strain. Three algal strains from the Solar Energy Research Institute (Golden, CO) collection were selected as good fixers of CO2 when the level of CO2 in the sparging gas was high. These algae also accumulated large amounts of crude lipids. SOx and NOx inhibited algal growth, but a green alga, Nannochloris sp. NANNO2 grew after a lag period, even when it received NO gas at the concentration of 300 ppm.

Carbonyl sulfide inhibition of CO dehydrogenase from Rhodospirillum rubrum.

Carbonyl sulfide (COS) has been investigated as a rapid-equilibrium inhibitor of CO oxidation by the CO dehydrogenase purified from Rhodospirillum rubrum. The kinetic evidence suggests that the inhibition by COS is largely competitive versus CO (Ki = 2.3 microM) and uncompetitive versus methylviologen as electron acceptor (Ki = 15.8 microM). The data are compatible with a ping-pong mechanism for CO oxidation and COS inhibition. Unlike the substrate CO, COS does not reduce the iron-sulfur centers of dye-oxidized CO dehydrogenase and thus is not an alternative substrate for the enzyme. However, like CO, COS is capable of protecting CO dehydrogenase from slow-binding inhibition by cyanide. A true binding constant (KD) of 2.2 microM for COS has been derived on the basis of the saturable nature of COS protection against cyanide inhibition. The ability of CO, CO2, COS, and related CO/CO2 analogues to reverse cyanide inhibition of CO dehydrogenase is also demonstrated. The kinetic results are interpreted in terms of two binding sites for CO on CO dehydrogenase from R. rubrum.

Carbonyl sulfide: an alternate substrate for but not an activator of ribulose-1,5-bisphosphate carboxylase.

Carbonyl sulfide, a competitive inhibitor of ribulose-bisphosphate carboxylase with respect to CO2 (Laing, W. A., and Christeller, J. T. (1980) Arch. Biochem. Biophys. 202, 592-600), is an alternate substrate. Thiocarboxylation was monitored by mass spectrometry as the stoichiometric consumption of carbonyl sulfide. The product, 1-thio-3-phosphoglycerate, was identified by 13C NMR and UV absorption spectroscopy and measured by enzymic conversion to thiolactate, coupled to the oxidation of NADH. The expected stoichiometry of thiocarboxylation was confirmed. The maximal rates of thiocarboxylation for the spinach and Rhodospirillum rubrum enzymes were close to the maximal rates of carboxylation for these two enzymes. Both enzymes favored CO2 over carbonyl sulfide (with Mg2+ as metal ion) by a factor of about 110. Thiocarboxylation could only be demonstrated with enzymes carbamylated with CO2. Incubation of the carbamylated E.ACO2.Mg complex with excess carbonyl sulfide caused the displacement of the activator carbamate. The thiocarbamylated enzyme was catalytically incompetent and did not form a stable quaternary complex with 2'-carboxyarabinitol bisphosphate. Incubation of the thiocarbamylated enzyme with excess CO2 resulted in the displacement of the thiocarbamate, the re-formation of the carbamylated E.ACO2.Mg complex and the restoration of catalytic competence. Computergraphic simulation of the thiocarbamylated quaternary complex indicated unfavorable van der Waals interactions associated with the thiocarbamate.