RESUMO
In the present study, we studied the distribution of silicate mineral weathering bacteria (SWB) in stressed environments that release potassium from insoluble source of mineral. Out of 972 isolates, 340 isolates were positive and mineral weathering potential ranged from 5.55 to 180.05%. Maximum abundance of SWB occurred 44.71% in saline environment followed by 23.53% in low temperature and 12.35% each in high temperature and moisture deficit. Among isolates, silicate mineral weathering efficiency ranged from 1.9 to 72.8 µg mL-1 available K in liquid medium. The phylogenetic tree of SWB discriminated in three clusters viz. Firmicutes, Proteobacteria and Actinobacteria. This is the first report on SWB in stressed environments and identified 27 genera and 67 species which is not reported earlier. Among them Bacillus was the predominant genera (58.60%) distantly followed by Pseudomonas (6.37%), Staphylococcus (5.10%) and Paenibacillus (4.46%). These bacterial strains could be developed as inoculants for biological replenishment of K in stressed soils. Graphical abstract.
Assuntos
Compostos de Alumínio/metabolismo , Bactérias/metabolismo , Compostos de Potássio/metabolismo , Silicatos/metabolismo , Microbiologia do Solo , Estresse Fisiológico , Bactérias/classificação , Filogenia , RNA Ribossômico 16S/genética , Estresse Salino , Solo/química , TemperaturaRESUMO
This study aimed to investigate in vitro and in vivo the influence of hyperglycemic condition on biocompatibility and biomineralization of gray mineral trioxide aggregate (GMTA) and white mineral trioxide aggregate (WMTA). For the in vitro study, fibroblast-like cells L929 were cultured under high or normal glucose concentration to investigate the effects of both MTA's on cell proliferation and inflammatory cytokines production IL-1ß, IL-6, and TNF-α. For the in vivo study, polyethylene tubes containing MTA materials and empty tubes were implanted into dorsal connective tissues of Wistar rats previously assigned normal and hyperglycemic. After 7 and 30 days, the tubes with surrounding tissues were removed and subjected to histological, fluorescence and immunohistochemical analyzes of IL-1ß, IL-6, and TNF-α. In vitro study showed that, under high glucose condition, GMTA reduced cell proliferation and IL-6 production compared with WMTA. Moreover, in vivo study revealed that hyperglycemic condition did not modify the inflammatory response and cytokines production in the tissue close to both materials. Independently of hyperglycemic status, mineralized areas were observed with both materials, but the fluorescence intensity of WMTA was diminished on 14 days in hyperglycemic animals. It is possible to conclude that GMTA was able to inhibit the proliferation rate and IL-6 production under high glucose concentration in vitro. Furthermore, cytokines production and inflammatory response were not upregulated in hyperglycemic animals; however, a decrease in the calcium deposition was observed in presence of WMTA, suggesting a delay in the mineralization process.
Assuntos
Compostos de Alumínio/química , Materiais Biocompatíveis/química , Glicemia/metabolismo , Compostos de Cálcio/química , Tecido Conjuntivo/metabolismo , Citocinas/metabolismo , Glucose/metabolismo , Óxidos/química , Silicatos/química , Aloxano/metabolismo , Compostos de Alumínio/metabolismo , Animais , Materiais Biocompatíveis/metabolismo , Biomineralização , Compostos de Cálcio/metabolismo , Proliferação de Células , Modelos Animais de Doenças , Combinação de Medicamentos , Fibroblastos/citologia , Humanos , Inflamação/metabolismo , Masculino , Óxidos/metabolismo , Ratos Wistar , Silicatos/metabolismo , Propriedades de Superfície , Fatores de TempoRESUMO
The climate, topography, fauna, and flora of Venezuela are highly diverse. However, limited information is currently available on the characterization of soybean rhizobia in Venezuela. To clarify the physiological and genetic diversities of soybean rhizobia in Venezuela, soybean root nodules were collected from 11 soil types located in different topographical regions. A total of 395 root nodules were collected and 120 isolates were obtained. All isolates were classified in terms of stress tolerance under different concentrations of NaCl and Al3+. The tolerance levels of isolates to NaCl and Al3+ varied. Based on sampling origins and stress tolerance levels, 44 isolates were selected for further characterization. An inoculation test indicated that all isolates showed the capacity for root nodulation on soybean. Based on multilocus sequence typing (MLST), 20 isolates were classified into the genera Rhizobium and Bradyrhizobium. The remaining 24 isolates were classified into the genus Burkholderia or Paraburkholderia. There is currently no evidence to demonstrate that the genera Burkholderia and Paraburkholderia are the predominant soybean rhizobia in agricultural fields. Of the 24 isolates classified in (Para) Burkholderia, the nodD-nodB intergenic spacer regions of 10 isolates and the nifH gene sequences of 17 isolates were closely related to the genera Rhizobium and Bradyrhizobium, respectively. The root nodulation numbers of five (Para) Burkholderia isolates were higher than those of the 20 α-rhizobia. Furthermore, among the 44 isolates tested, one Paraburkholderia isolate exhibited the highest nitrogen-fixation activity in root nodules.
Assuntos
Burkholderiaceae/classificação , Burkholderiaceae/isolamento & purificação , Glycine max/microbiologia , Filogenia , Microbiologia do Solo , Compostos de Alumínio/metabolismo , Bradyrhizobium/classificação , Bradyrhizobium/genética , Bradyrhizobium/isolamento & purificação , Bradyrhizobium/fisiologia , Burkholderia/classificação , Burkholderia/genética , Burkholderia/isolamento & purificação , Burkholderia/fisiologia , Burkholderiaceae/genética , Burkholderiaceae/fisiologia , Clima , Genes Bacterianos/genética , Geografia , Tipagem de Sequências Multilocus , Fixação de Nitrogênio/genética , Nodulação , Rhizobium/classificação , Rhizobium/genética , Rhizobium/isolamento & purificação , Rhizobium/fisiologia , Nódulos Radiculares de Plantas/microbiologia , Cloreto de Sódio/metabolismo , Estresse Fisiológico , Simbiose , VenezuelaRESUMO
Mineral trioxide aggregate (MTA) is a powder aggregate containing mineral oxides with a good biological action and may facilitate the regeneration of the periodontal ligament and formation of bone. Calcium hydroxide demonstrates antibacterial properties, enhances tissue dissolution, and induces bone formation. The objective of this study was to evaluate the MTA in the bone healing process and verify if the calcium hydroxide P.A. can improve and accelerate this process. It was used forty male Wistar rats, which were divided into two groups, considering or not the use of calcium hydroxide P.A. solution before treatment. Thus, each one of these groups was divided in four groups with five animals each, according to the treatment and the defect filled by: animal's coagulum, monoolein gel, MTA in aqueous solution, and MTA combined with monoolein gel. After 10 days, the animals were perfused and the right hemimandibles removed for histological analysis. Statistical analysis of the data showed significant difference between all analyzed groups when it was made comparisons using or not calcium hydroxide P.A. (p<0.0001). There was found statistical difference between the groups that was inserted or not MTA, independently the calcium hydroxide application (p<0.05). Results showed that the MTA used was able to induce bone regeneration and had its action optimized when combined to calcium hydroxide P.A.
Assuntos
Compostos de Alumínio/metabolismo , Osso e Ossos/efeitos dos fármacos , Osso e Ossos/fisiologia , Compostos de Cálcio/metabolismo , Hidróxido de Cálcio/farmacologia , Portadores de Fármacos/uso terapêutico , Osteogênese/fisiologia , Óxidos/metabolismo , Silicatos/metabolismo , Animais , Osso e Ossos/lesões , Combinação de Medicamentos , Masculino , Mandíbula/citologia , Mandíbula/fisiologia , Osteogênese/efeitos dos fármacos , Ratos , Ratos WistarRESUMO
G-protein alpha subunits consist of two domains: a Ras-like domain also called GTPase domain (GTPaseD), structurally homologous to monomeric G-proteins, and a more divergent domain, unique to heterotrimeric G-proteins, called helical domain (HD). G-protein activation, requires the exchange of bound GDP for GTP, and since the guanine nucleotide is buried in a deep cleft between both domains, it has been postulated that activation may involve a conformational change that will allow the opening of this cleft. Therefore, it has been proposed, that interdomain interactions are playing an important role in regulating the nucleotide exchange rate of the alpha subunit. While constructing different Gs(alpha) quimeras, we identified a Gs(alpha) random mutant, which was very inefficient in stimulating adenylyl cyclase activity. The introduced mutation corresponded to the substitution of Ser(111) for Asn (S111N), located in the carboxi terminal end of helix A of the HD, a region neither involved in AC interaction nor in the interdomain interface. In order to characterize this mutant, we expressed it in bacteria, purified it by niquel-agarose chromatography, and studied its nucleotide exchange properties. We demonstrated that the recombinant S111N Gs(alpha) was functional since it was able to undergo the characteristic conformational change upon GTP binding, detected by the acquisition of a trypsin-resistant conformation. When the biochemical properties were determined, the mutant protein exhibited a reduced GDP dissociation kinetics and as a consequence a slower GTPgammaS binding rate that was responsible for a diminished adenylyl cyclase activation when GTPgammaS was used as activator. These data provide new evidence that involves the HD as a regulator of Gs(alpha) function, in this case the alphaA helix, which is not directly involved with the nucleotide binding site nor the interdomain interface.
Assuntos
Subunidades alfa Gs de Proteínas de Ligação ao GTP/genética , Subunidades alfa Gs de Proteínas de Ligação ao GTP/metabolismo , Guanosina Difosfato/metabolismo , Guanosina Trifosfato/metabolismo , Mutação Puntual , Adenilil Ciclases/metabolismo , Compostos de Alumínio/metabolismo , Substituição de Aminoácidos , Asparagina/genética , Fluoretos/metabolismo , Subunidades alfa Gs de Proteínas de Ligação ao GTP/isolamento & purificação , Proteínas de Ligação ao GTP/metabolismo , Guanosina 5'-O-(3-Tiotrifosfato)/metabolismo , Humanos , Modelos Moleculares , Conformação Proteica , Estrutura Secundária de Proteína/fisiologia , Estrutura Terciária de Proteína/fisiologia , Receptores de Superfície Celular/metabolismo , Serina/genética , Tripsina/metabolismoRESUMO
Aluminum (Al) toxicity has been mainly investigated in uremic patients although healthy subjects and patients without renal insufficiency are not exempt from its potential deleterious effects. This experimental study aims to elucidate the action of different doses of Al citrate on in vivo erythropoiesis and find out whether the metal exerts a local toxic effect upon the bone marrow late erythroid progenitor cells. The groups in the first experimental series were: C1 (n=5) controls and TAl-1 (n=5) rats receiving 1 micromol Al citrate/g body weight/day by gavage. Colony-forming units-erythroid (CFU-E) development was inhibited in the TAl-1 group, but the median osmotic fragility (MOF) and hematocrit (Ht) values were similar to those of the C1 group. The groups in the second series were C2 (n=5) controls and TAl-2 (n=5) rats receiving Al citrate in drinking water (100 mmol/l). The TAl-2 group showed decreased Ht, hemoglobin concentration, MOF and red blood-cell life-span values (P<0.05), and a marked inhibition of the CFU-E development (P<0.01). Serum and bone Al concentrations were increased in both Al-treated groups (P < 0.01). There was a dose-dependent increase in bone Al levels (P < 0.01) and a dose-dependent decrease of CFU-E development (P<0.05). The CFU-E development was inversely correlated with the bone Al content (r=-0.79; P<0.05). The results demonstrate that even very low doses of Al citrate impair erythropoiesis in vivo and higher doses exert a deleterious action on both CFU-E and mature erythrocytes. This might show a local effect of Al on CFU-E caused by the bone sensitivity to the metal accumulation.