RESUMO
Inorganic forms of As (arsenite - As(III) and arsenate - As(V)) are prevalent in soil and recognized for their high toxicity. Once in the soil, these forms of As can compromise key organisms for ecological processes, such as earthworms. The aim of the study was to evaluate the toxicity of arsenite and arsenate in the Californian earthworm Eisenia andrei exposed in natural soil and tropical artificial soil (TAS). Adverse effects were evaluated using avoidance test, acute toxicity test, and a sublethal concentration test to assess biochemical parameters. LC50 values for arsenite were 21.27 mg/kg in natural soil and 19.0 mg/kg in TAS and for arsenate were 76.18 mg/kg in natural soil and above 120 mg/kg in TAS. In the avoidance test, this behavior was shown to be significantly higher in the natural soil and for earthworms exposed to arsenite, while total antioxidant capacity, glutathione levels, lipid damage, and DNA damage were significantly higher in animals exposed to arsenite, but without differences in relation to the two types of soil tested. Animals exposed to As(V) showed increased activity of enzymes related to glutathione metabolism. The results obtained in the present study show the impact of As exposure on the health of the Californian earthworm E. andrei, especially in the form of arsenite, and alert the public authorities that legal limits should, whenever possible, consider the soil properties and also the different chemical species of the contaminants.
Assuntos
Arsenitos , Oligoquetos , Poluentes do Solo , Animais , Solo/química , Arseniatos/toxicidade , Arseniatos/metabolismo , Arsenitos/toxicidade , Arsenitos/metabolismo , Poluentes do Solo/análiseRESUMO
Aquatic animals are vulnerable to arsenic (As) toxicity. However, rarely does a contaminant occur alone in the aquatic environment. For this reason, this study was conducted to evaluate whether titanium dioxide nanoparticles (nTiO2) can interfere with the effects induced by As in Litopenaeus vannamei. Arsenic accumulation and metabolic capacity; expression and enzymatic activity of GSTΩ (glutathione-S-transferase omega isoform); antioxidant responses such as GSH, GR, and GST (reduced glutathione levels, glutathione reductase, and glutathione-S-transferase activity, respectively); and lipid peroxidation in the gills and hepatopancreas of shrimp were evaluated. The results are summarized as follows: (1) higher accumulation of As occurred in both tissues after exposure to As alone; (2) co-exposure to nTiO2 affected the capacity to metabolize As; (3) GSTΩ gene expression was not modified, but its activity was decreased by co-exposure to both contaminants; (4) As alone increased the GSH levels in the hepatopancreas, and co-exposure to nTiO2 reduced these levels in both tissues; (5) a decrease in the GST activity in the gills occurred with all treatments; (6) in the gills, GR activity was increased by As, and nTiO2 reversed this increase, whereas in the hepatopancreas co-exposure inhibited enzyme activity; (7) only in the hepatopancreas lipid damage was observed when animals were exposed to As or nTiO2 but not in co-exposure. The results showed that the As induces toxic effects in both tissues of shrimp and that co-exposure to nTiO2 can potentiate these effects and decrease the capacity to metabolize As, favoring the accumulation of more toxic compounds.
Assuntos
Antioxidantes/metabolismo , Arsenitos/toxicidade , Nanopartículas Metálicas/toxicidade , Estresse Oxidativo/efeitos dos fármacos , Penaeidae/efeitos dos fármacos , Compostos de Sódio/toxicidade , Titânio/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Arsenitos/metabolismo , Brânquias/efeitos dos fármacos , Brânquias/metabolismo , Hepatopâncreas/efeitos dos fármacos , Hepatopâncreas/metabolismo , Peroxidação de Lipídeos/efeitos dos fármacos , Penaeidae/metabolismo , Compostos de Sódio/metabolismo , Distribuição Tecidual , Poluentes Químicos da Água/metabolismoRESUMO
In fish of freshwaters environments, the accumulation and toxic effects of arsenite (AsIII) can be attenuated by detoxification proteins such as GST and ABCC transporters. We studied the effects of AsIII on the middle intestine of O. mykiss in ex-vivo and in vivo/ex vivo assays. For the ex vivo assays, we measured the transport rate of the ABCC substrate DNP-SG and GST activity in intestinal strips and everted sacs. AsIII inhibited DNP-SG transport in a concentration-dependent manner, specifically when we applied it on the basolateral side. GST activity increased when we applied a maximum concentration of AsIII. For the in vivo/ex vivo assays, we kept fish in water with or without 7.7⯵molâ¯L-1 of AsIII for 48â¯h. Then, we measured DNP-SG transport rate, GST activity, and PP1 activity in intestine strips during one hour. For PP1 activity, we incubated the strips with or without microcystin-LR (MCLR), a toxin excreted through ABCC2 proteins. We also analyzed Abcc2 and Gst-π mRNA expression in intestine and liver tissue. In the group exposed in vivo to AsIII, DNP-SG transport rate and GST activity were higher and the effect of MCLR over PP1 activity was attenuated. AsIII significantly induced only Abcc2 mRNA expression in both middle intestine and liver. Our results suggest that, in the middle intestine of O. mykiss, AsIII is absorbed mainly at the basolateral side of the enterocytes, excreted to the lumen by ABCC2 transporters, and is capable of modulating Abcc2 mRNA expression by a transcriptional mechanism.
Assuntos
Transportadores de Cassetes de Ligação de ATP/metabolismo , Arsenitos , Glutationa S-Transferase pi/metabolismo , Intestinos/enzimologia , Fígado/metabolismo , Oncorhynchus mykiss/metabolismo , Animais , Arsenitos/metabolismo , Arsenitos/farmacocinética , Arsenitos/toxicidade , Proteínas de Peixes/metabolismo , Regulação da Expressão Gênica , RNA Mensageiro , Xenobióticos/metabolismo , Xenobióticos/farmacocinética , Xenobióticos/toxicidadeRESUMO
Aiming at revealing the arsenic (As) resistance of the endophytic Kocuria strains isolated from roots and stems of Sphaeralcea angustifolia grown at mine tailing, four strains belonging to different clades of Kocuria based upon the phylogeny of 16S rRNA genes were screened for minimum inhibitory concentration (MIC). Only the strain NE1RL3 was defined as an As-resistant bacterium with MICs of 14.4/0.0125 mM and 300/20.0 mM for As3+ and As5+, respectively, in LB/mineral media. This strain was identified as K. palustris based upon analyses of cellular chemical compositions (cellular fatty acids, isoprenoides, quinones, and sugars), patterns of carbon source, average nucleotide identity of genome and digital DNA-DNA relatedness. Six genes coding to enzymes or proteins for arsenate reduction and arsenite-bumping were detected in the genome, demonstrating that this strain is resistant to As possibly by reducing As5+ to As3+, and then bumping As3+ out of the cell. However, this estimation was not confirmed since no arsenate reduction was detected in a subsequent assay. This study reported for the first time the presence of phylogenetically distinct arsenate reductase genes in a Kocuria strain and evidenced the possible horizontal transfer of these genes among the endophytic bacteria.
Assuntos
Arseniato Redutases/genética , Arseniatos/metabolismo , Micrococcaceae/enzimologia , Micrococcaceae/genética , Arsênio/farmacologia , Arsenitos/metabolismo , Testes de Sensibilidade Microbiana , Micrococcaceae/metabolismo , Filogenia , RNA Ribossômico 16S/genética , Traqueófitas/microbiologiaRESUMO
Microorganisms associated with plants have a great biotechnological potential, but investigations of these microorganisms associated with native plants in peculiar environments has been incipient. The objective of this study was to analyze the plant growth-promoting bacteria potential of cultivable bacteria associated with rare plants from the ferruginous rocky fields of the Brazilian Iron Quadrangle. The roots and rhizospheres of nine endemic plants species and samples of a root found in a lateritiric duricrust (canga) cave were collected, the culturable bacteria isolated and prospected for distinct biotechnological and ecological potentials. Out of the 148 isolates obtained, 8 (5.4%) showed potential to promote plant growth, whereas 4 (2.7%) isolates acted as biocontrol agents against Xanthomonas citri pathotype A (Xac306), reducing the cancrotic lesions by more than 60% when co-inoculated with this phytopathogen in Citrus sinensis plants. Moreover, other 4 (2.7%) isolates were classified as potential bioremediation agents, being able to withstand high concentrations of arsenite (5 mM As3+) and arsenate (800 mM As5+), by removing up to 35% and 15% of this metalloid in solution, respectively. These same four isolates had a positive influence on the growth of both the roots and the aerial parts when inoculated with tomato seeds in the soil contaminated with arsenic. This is the first time that an investigation highlights the potentialities of bacteria associated with rare plants of ferruginous rocky fields as a reservoir of microbiota of biotechnological and ecological interest, highlighting the importance of conservation of this area that is undergoing intense anthropic activity.
Assuntos
Bactérias/metabolismo , Fenômenos Fisiológicos Bacterianos , Biotecnologia , Desenvolvimento Vegetal/fisiologia , Raízes de Plantas/microbiologia , Rizosfera , Amilases/metabolismo , Arseniatos/metabolismo , Arsênio/metabolismo , Arsênio/farmacologia , Arsenitos/metabolismo , Bactérias/classificação , Bactérias/efeitos dos fármacos , Bactérias/genética , Biodegradação Ambiental , Biodiversidade , Agentes de Controle Biológico , Brasil , Resistência a Medicamentos , Fertilizantes , Cianeto de Hidrogênio/metabolismo , Ácidos Indolacéticos/metabolismo , Solanum lycopersicum/crescimento & desenvolvimento , Solanum lycopersicum/microbiologia , Microbiota/fisiologia , Fixação de Nitrogênio , Peptídeo Hidrolases/metabolismo , Fosfatos/metabolismo , Doenças das Plantas/microbiologia , Doenças das Plantas/prevenção & controle , Patologia Vegetal , Raízes de Plantas/química , RNA Ribossômico 16S/genética , Sideróforos/metabolismo , Solo/química , Microbiologia do Solo , Poluentes do Solo/análise , Poluentes do Solo/metabolismo , Xanthomonas/fisiologiaRESUMO
The Burkholderia xenovorans LB400 multireplicon genome displays a relatively high proportion of redundant genes, including several genes predicted to be related to arsenic resistance. These comprise an ars gene cluster, composed of the arsR3, acr3, arsC1 and arsH genes, as well as two arsB, arsC2, and seven individual arsR genes. The objective of this work was to elucidate the involvement of the ars gene cluster in arsenic resistance by the LB400 strain. Susceptibility tests showed that B. xenovorans LB400 is highly resistant to arsenate and arsenite. Arsenic resistance was induced by prior exposure of LB400 to arsenate or arsenite. reverse transcription-polymerase chain reaction assays using total RNA from LB400 showed arsenite-induced transcription of the arsR3 gene, suggesting that the ars gene cluster constitutes an arsenite-responsive operon. Transfer of cloned LB400 ars genes to heterologous Escherichia coli or Pseudomonas aeruginosa strains demonstrated that the ArsR3 transcriptional repressor, ArsC1 arsenate reductase, and the Acr3 arsenite efflux pump encoded in the LB400 ars gene cluster, are all associated to the arsenic resistance phenotype of this strain. The ars gene cluster from Burkholderia xenovorans LB400 is responsible for the inducible arsenic-resistance phenotype of the bacterium.
Assuntos
Arsênio/metabolismo , Proteínas de Bactérias/genética , Burkholderia/genética , Farmacorresistência Bacteriana/genética , Família Multigênica/genética , Arseniato Redutases/genética , Arseniatos/metabolismo , Arseniatos/toxicidade , Arsênio/toxicidade , Arsenitos/metabolismo , Arsenitos/toxicidade , Proteínas de Bactérias/metabolismo , Sequência de Bases , Burkholderia/efeitos dos fármacos , Burkholderia/crescimento & desenvolvimento , Clonagem Molecular , DNA Bacteriano/análise , Escherichia coli/genética , Regulação Bacteriana da Expressão Gênica , Testes de Sensibilidade Microbiana , Óperon , Fenótipo , Filogenia , Pseudomonas aeruginosa/genética , Alinhamento de Sequência , Análise de Sequência de Proteína , Transativadores/genéticaRESUMO
Mine tailings and wastewater generate man-made environments with several selective pressures, including the presence of heavy metals, arsenic and high cyanide concentrations, but severe nutritional limitations. Some oligotrophic and pioneer bacteria can colonise and grow in mine wastes containing a low concentration of organic matter and combined nitrogen sources. In this study, Pseudomonas mendocina P6115 was isolated from mine tailings in Durango, Mexico, and identified through a phylogenetic approach of 16S rRNA, gyrB, rpoB, and rpoD genes. Cell growth, cyanide consumption, and ammonia production kinetics in a medium with cyanide as sole nitrogen source showed that at the beginning, the strain grew assimilating cyanide, when cyanide was removed, ammonium was produced and accumulated in the culture medium. However, no clear stoichiometric relationship between both nitrogen sources was observed. Also, cyanide complexes were assimilated as nitrogen sources. Other phenotypic tasks that contribute to the strain's adaptation to a mine tailing environment included siderophores production in media with moderate amounts of heavy metals, arsenite and arsenate tolerance, and the capacity of oxidizing arsenite. P. mendocina P6115 harbours cioA/cioB and aoxB genes encoding for a cyanide-insensitive oxidase and an arsenite oxidase, respectively. This is the first report where P. mendocina is described as a cyanotrophic and arsenic oxidizing species. Genotypic and phenotypic tasks of P. mendocina P6115 autochthonous from mine wastes are potentially relevant for biological treatment of residues contaminated with cyanide and arsenic.
Assuntos
Arsênio/metabolismo , Cianetos/metabolismo , Pseudomonas mendocina/metabolismo , Microbiologia do Solo , Amônia/metabolismo , Arsênio/análise , Arsenitos/análise , Arsenitos/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Cianetos/análise , México , Mineração , Oxirredutases/genética , Oxirredutases/metabolismo , Filogenia , Pseudomonas mendocina/classificação , Pseudomonas mendocina/genética , Pseudomonas mendocina/isolamento & purificação , RNA Ribossômico 16S/genéticaRESUMO
Arsenic contamination is an important environmental problem around the world since its high toxicity, and bacteria resist to this element serve as valuable resource for its bioremediation. Aiming at searching the arsenic-resistant bacteria and determining their resistant mechanism, a total of 27 strains isolated from roots of Prosopis laevigata and Spharealcea angustifolia grown in a heavy metal-contaminated region in Mexico were investigated. The minimum inhibitory concentration (MIC) and transformation abilities of arsenate (As5+) and arsenite (As3+), arsenophore synthesis, arsenate uptake, and cytoplasmatic arsenate reductase (arsC), and arsenite transporter (arsB) genes were studied for these strains. Based on these results and the 16S rDNA sequence analysis, these isolates were identified as arsenic-resistant endophytic bacteria (AREB) belonging to the genera Arthrobacter, Bacillus, Brevibacterium, Kocuria, Microbacterium, Micrococcus, Pseudomonas, and Staphylococcus. They could tolerate high concentrations of arsenic with MIC from 20 to > 100 mM for As5+ and 10-20 mM for As3+. Eleven isolates presented dual abilities of As5+ reduction and As3+ oxidation. As the most effective strains, Micrococcus luteus NE2E1 reduced 94% of the As5+ and Pseudomonas zhaodongensis NM2E7 oxidized 46% of As3+ under aerobic condition. About 70 and 44% of the test strains produced arsenophores to chelate As5+ and As3+, respectively. The AREB may absorb arsenate via the same receptor of phosphate uptake or via other way in some case. The cytoplasmic arsenate reductase and alternative arsenate reduction pathways exist in these AREB. Therefore, these AREB could be candidates for the bioremediation process.
Assuntos
Arsênio/metabolismo , Bactérias/isolamento & purificação , Endófitos/metabolismo , Magnoliopsida/microbiologia , Prosopis/microbiologia , Arseniatos/metabolismo , Arsenitos/metabolismo , Bactérias/classificação , Bactérias/genética , Bactérias/metabolismo , Biodegradação Ambiental , DNA Ribossômico/genética , Endófitos/classificação , Endófitos/genética , Endófitos/isolamento & purificação , Magnoliopsida/metabolismo , México , Mineração , Filogenia , Raízes de Plantas/metabolismo , Raízes de Plantas/microbiologia , RNA Ribossômico 16S/genéticaRESUMO
Uptake of Arsenic (As) in plant tissues can affect metabolism, causing physiological disorders, even death. As toxicity, but also pathogen infections trigger a generalised stress response called oxidative stress; however knowledge on the response of soybean (Glycine max L.) under multiple stressors is limited so far. Arbuscular mycorrhizal fungi (AMF) enhance the tolerance of host plants to abiotic and biotic stress. Thus, we investigated the effects of the AMF Rhizophagus intraradices on soybean grown in As-contaminated soils as well as in the presence of the pathogen Macrophomina phaseolina (charcoal rot of the stem). Plant parameters and degree of mycorrhizal colonization under the different assessed treatments were analyzed. Content of As in roots and leaves was quantified. Increasing As level in the soil stopped plant growth, but promoted plant As uptake. Inoculation of soybean plants with M. phaseolina accentuated As effect at all physiological levels. In the presence of mycorrhizal symbiosis biomass dramatically increased, and significantly reduced the As concentration in plant tissues. Mycorrhization decreased oxidative damage in the presence of both As and the pathogen. Furthermore, transcription analysis revealed that the high-affinity phosphate transporter from R. intraradices RiPT and the gene encoding a putative arsenic efflux pump RiArsA were up-regulated under higher As doses. These results suggest that R. intraradices is most likely to get involved in the defense response against M. phaseolina, but also in the reduction of arsenate to arsenite as a possible detoxification mechanism in AMF associations in soybean. CAPSULE ABSTRACT: R. intraradices actively participates in the soybean antioxidant defense response against arsenic stress and M. phaseolina infection.
Assuntos
Arsênio/toxicidade , Glomeromycota/fisiologia , Glycine max/efeitos dos fármacos , Micorrizas/fisiologia , Poluentes do Solo/toxicidade , Arseniatos/metabolismo , Arsênio/análise , Arsenitos/metabolismo , Ascomicetos/fisiologia , Biomassa , Micorrizas/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Desenvolvimento Vegetal , Folhas de Planta/química , Raízes de Plantas/química , Solo , Poluentes do Solo/análise , Glycine max/metabolismo , SimbioseRESUMO
Yeasts were quantified and isolated from the rhizospheres of 5 plant species grown at 2 sites of a Mexican region contaminated with arsenic, lead, and other heavy metals. Yeast abundance was about 10(2) CFU/g of soil and 31 isolates were obtained. On the basis of the phylogenetic analysis of 26S rRNA and internal transcribed spacer fragment, 6 species were identified within the following 5 genera: Cryptococcus (80.64%), Rhodotorula (6.45%), Exophiala (6.45%), Trichosporon (3.22%), and Cystobasidium (3.22%). Cryptococcus spp. was the predominant group. Pectinases (51.6%), proteases (51.6%), and xylanases (41.9%) were the enzymes most common, while poor production of siderophores (16.1%) and indole acetic acid (9.67%) was detected. Isolates of Rhodotorula mucilaginosa and Cystobasidium sloffiae could promote plant growth and seed germination in a bioassay using Brassica juncea. Resistance of isolates by arsenic and heavy metals was as follows: As(3+) ≥ 100 mmol/L, As(5+) ≥ 30 mmol/L, Zn(2+) ≥ 2 mmol/L, Pb(2+) ≥ 1.2 mmol/L, and Cu(2+) ≥ 0.5 mmol/L. Strains of Cryptococcus albidus were able to reduce arsenate (As(5+)) into arsenite (As(3+)), but no isolate was capable of oxidizing As(3+). This is the first study on the abundance and identification of rhizosphere yeasts in a heavy-metal- and arsenic-contaminated soil, and of the reduction of arsenate by the species C. albidus.