Arsenic resistant bacteria isolated from agricultural soils of Bangladesh and characterization of arsenate reducing strains

Aims: To analyse the arsenic-resistant bacterial communities of two agricultural soils of Bangladesh, to isolate arsenic-resistant bacteria, to study their potential role in arsenic transformation and to investigate the genetic determinants for arsenic resistance among the isolates. Methods and Results: Enrichment cultures were performed in a minimal medium in the presence of As(III) and As(V) to isolate resistant bacteria. Twenty-one arsenic-resistant bacteria belonging to different genera of Gram-positive and Gram-negative bacteria were isolated. The isolates, with the exception of Oceanimonas doudoroffii Dhal Rw, reduced 2 mmol l 121 As(V) completely to As(III) in aerobic conditions. Putative gene fragments for arsenite efflux pumps were amplified in isolates from Dhal soil and a putative arsenate reductase gene fragment was amplified from a Bacillus sp. from Rice soil. Conclusions: Phylogenetically diverse arsenic-resistant bacteria present in agricultural soils of Bangladesh are capable of reducing arsenate to arsenite under aerobic conditions apparently for detoxification purpose. Significance and Impact of the Study: This study provides results on identification, levels of arsenic resistance and reduction of arsenate by the bacterial isolates which could play an important role in arsenic cycling in the two arsenic-contaminated soils in Bangladesh

Role of PGP arsenic-resistant bacteria in As mobilization and translocation in Helianthus annuus L

This study investigated the effect of arsenic-resistant Alcaligenes sp. strain DhalL with potential plant growth promoting characteristics on growth and arsenic uptake by sunflower ( Helianthus annuus L.). Pot experiments were prepared using an agricultural As-contaminated soil sown with seeds of sunflower uninoculated and inoculated with the strain. A Real Time PCR method, based on the quantification of ACR3( 2) gene carried by DhalL, was set up in order to monitor presence and colonisation of the soil by the strain. The arsenic content was significantly higher in inoculated than in the uninoculated aboveground part of the plants (1.63 mg kg d.w. -1 vs. 0.77), highlighting the effect of the strain on arsenic uptake by sunflower. ACR3( 2) gene copy number was one hundred times higher in inoculated than in uninoculated pots, especially in the rhizospheric soil, indicating that colonisation occurred. The results suggest that the presence of arsenic resistant strain such as Alcaligenes sp. DhalL in the rhizosphere of sunflower could influence As mobilization and uptake by plant

Evolution of a degradative bacterial consortium during the enrichment of naphtha solvent

A microbial mixed culture able to degrade naphtha solvent, a model of hydrocarbon aromatic mixture, was isolated from a hydrocarbon-polluted soil. Composition of the population was monitored by phenotypic and molecular methods applied on soil DNA, on whole enrichment culture DNA, and on 85 isolated strains. Strains were characterized for their 16S rDNA restriction profiles and for their random amplified polymorphic DNA profiles. Catabolic capabilities were monitored by phenotypic traits and by PCR assays for the presence of the catabolic genes methyl mono-oxygenase ( xylA,M), catechol 2,3 dioxygenase (xylE) and toluene dioxygenase (todC1) of TOL and TOD pathways. Different haplotypes belonging to Pseudomonas putida, Ps. aureofaciens and Ps. aeruginosa were found to degrade aromatic compounds and naphtha solvent. The intrinsic catabolic activity of the microbial population of the polluted site was detected by PCR amplification of the xylE gene directly from soil DNA

Arsenic transforming abilities of groundwater bacteria and the combined use of Aliihoeflea sp. strain 2WW and goethite in metalloid removal

Several technologies have been developed for lowering arsenic in drinking waters below the World Health Organization limit of 10 \u3bcg/L. When in the presence of the reduced form of inorganic arsenic, i.e. arsenite, one options is pre-oxidation of arsenite to arsenate and adsorption on iron-based materials. Microbial oxidation of arsenite is considered a sustainable alternative to the chemical oxidants. In this contest, the present study investigates arsenic redox transformation abilities of bacterial strains in reductive groundwater from Lombardia (Italy), where arsenite was the main arsenic species. Twenty isolates were able to reduce 75 mg/L arsenate to arsenite, and they were affiliated to the genera Pseudomonas, Achromobacter and Rhodococcus and genes of the ars operon were detected. Three arsenite oxidizing strains were isolated: they belonged to Rhodococcus sp., Achromobacter sp. and Aliihoeflea sp., and aioA genes for arsenite oxidase were detected in Aliihoeflea sp. strain 2WW and in Achromobacter sp. strain 1L. Uninduced resting cells of strain 2WW were used in combination with goethite for arsenic removal in a model system, in order to test the feasibility of an arsenic removal process. In the presence of 200 \u3bcg/L arsenite, the combined 2WW-goethite system removed 95% of arsenic, thus lowering it to 8 \u3bcg/L. These results indicate that arsenite oxidation by strain 2WW combined to goethite adsorption is a promising approach for arsenic removal from contaminated groundwater

Assessment of bacterial community structure in a long-term copper-polluted ex vineyard soil

The influence of long-term copper contamination on the diversity of bacterial communities was investigated in an ex-vineyard soil. Two sites of the same area but exhibiting different 3-fold exchangeable copper (Ex-Cu) concentrations were analysed. Culturable bacterial community structure was assessed using a variety of approaches: determination of culturable bacteria number, analyses of 132 isolates, and denaturing gradient gel electrophoresis (DGGE) patterns of bacterial biomass grown on agar plates and of soil DNA. There was no significant difference in the number of total heterotrophs at the two sites, whereas the percentage of fast-growing bacteria growing in 1 day, was lower at the site with the higher Ex-Cu content. A high percentage of Cu-tolerant bacteria was found in both sites (63-70%) and it was relatively independent of the Cu content. Shifts in species composition of the culturable bacterial community were detected by analysing isolates from the two soils, Gram-positive bacteria prevailed in the less-polluted soil while Gram-negative bacteria in the more-polluted soil. Each sample site had a community with a different metal resistance pattern. Our study seems to indicate that in this soil ecosystem, copper influenced the culturable bacterial communities, affecting the structural diversity and altering some of the metal resistance of the microorganisms. The Sorensen similarity index calculated on DGGE profiles of 16S rDNA of total and culturable bacterial communities indicated a different species composition at the two sites, although both sites had the same biodiversity degree and different dominance

Patho- physiological role of BDNF in fibrin clotting

Circulating levels of Brain Derived Neurotrophic Factor (BDNF) are lower in coronary heart disease (CHD) than in healthy subjects and are associated with coronary events and mortality. However, the mechanism(s) underling this association is not fully understood. We hypothesize that BDNF may influence fibrin fiber structure and clot stability, favoring clot lysis and thrombus resolution. We showed that recombinant BDNF (rh-BDNF) influenced with clot formation in a concentration-dependent manner in both purified fibrinogen and plasma from healthy subjects. In particular, rh-BDNF reduced the density of fibrin fibers, the maximum clot firmness (MCF) and the maximum clot turbidity, and affected the lysis of clot. In addition, both thrombin and reptilase clotting time were prolonged by rh-BDNF, despite the amount of thrombin formed was greater. Intriguingly, CHD patients had lower levels of BDNF, greater fibrin fibers density, higher MCF than control subjects, and a negative correlation between BDNF and MCF was found. Of note, rh-BDNF markedly modified fibrin clot profile restoring physiological clot morphology in CHD plasma. In conclusion, we provide evidence that low levels of BDNF correlate with the formation of bigger thrombi (in vitro) and that this effect is mediated, at least partially, by the alteration of fibrin fibers formation

Degradation of 2,4,6-trichlorophenol by a specialized organism and by indigenous soil microflora: bioaugmentation and self-remediability for soil restoration

A selected mixed culture and a strain of Alcaligenes eutrophus TCP were able to totally degrade 2,4,6-TCP with stoichiometric release of Cl-. In cultures of Alc. eutrophus TCP, a dioxygenated dichlorinated metabolite was detected after 48 h of incubation. Experiments conducted with soil microcosms gave evidence that: the degradative process had a biotic nature and was accompanied by microbial growth; the soil used presented an intrinsic degradative capacity versus 2,4,6-TCP; the specialized organism used as inoculum was effective in degrading 2,4,6-TCP in a short time. These results could be utilized for the adoption of appropriate remediation techniques for contaminated soil

Endothelial Dysfunction in Patients with Severe Mitral Regurgitation

Mitral valve prolapse (MVP) is the most common cause of severe mitral regurgitation. It has been reported that MVP patients-candidates for mitral valve repair (MVRep)-showed an alteration in the antioxidant defense systems as well as in the L-arginine metabolic pathway. In this study, we investigate if oxidative stress and endothelial dysfunction are an MVP consequence or driving factors. Forty-five patients undergoing MVRep were evaluated before and 6 months post surgery and compared to 29 controls. Oxidized (GSSG) and reduced (GSH) forms of glutathione, and L-arginine metabolic pathway were analyzed using liquid chromatography-tandem mass spectrometry methods while osteoprotegerin (OPG) through the ELISA kit and circulating endothelial microparticles (EMP) by flow cytometry. Six-month post surgery, in MVP patients, the GSSG/GSH ratio decreased while symmetric and asymmetric dimethylarginines levels remained comparable to the baseline. Conversely, OPG levels significantly increased when compared to their baseline. Finally, pre-MVRep EMP levels were significantly higher in patients than in controls and did not change post surgery. Overall, these results highlight that MVRep completely restores the increased oxidative stress levels, as evidenced in MVP patients. Conversely, no amelioration of endothelial dysfunction was evidenced after surgery. Thus, therapies aimed to restore a proper endothelial function before and after surgical repair could benefit MVP patients

New insights into the biodegradation of thiodiglycol, the hydrolysis product of Yperite (sulfur mustard gas)

Aims: To isolate thiodiglycol (TDG)-degrading bacteria, the mustard gas hydrolysis product, and to characterize the metabolites formed and the enzymes involved in the degradation. Methods and Results: Two strains, identified as Achromobacter xylosoxydans G5 and Paracoccus denitrificans E4, isolated from a petroleum-contaminated soil, utilized TDG as sole carbon and sulfur source. During the degradation of TDG by strain E4 [(2-hydroxyethyl)thio] acetic acid (HETA), thiodiglycolic acid (TDGA) and bis-(2-hydroxyethyl)disulfide (BHEDS) were identified by gas chromatography\u2013mass spectrometry analysis, while HETA and TDGA were identified for strain G5. Two-dimensional isoelectric focussing-gel electrophoresis (2-D IEF/SDS\u2013PAGE) maps of protein extracts of P. denitrificans E4 grown on TDG showed a spot identified as a methanol dehydrogenase. Increased expression of a putative iscS gene, involved in sulfur assimilation, was observed in TDG-grown cells of A. xylosoxydans G5. Conclusions: TDG degradation by P. denitrificans E4 occurred through two pathways: one involved cleavage of the C\u2013S bond of HETA, yielding BHEDS and the other, oxidation of the alcoholic groups of TDG, yielding TDGA. The cleavage of the C\u2013S bond of TDGA gave mercaptoacetic acid, further oxidized to acetate and sulfate. Significance and Impact of the Study: Increased knowledge of TDG-degrading bacteria and the possibility of using them in a tailored-two-stage mustard gas destruction process