RESUMO
Plant growth-promoting bacteria have been highlighted by their potential for application in plant production, allowing the reduction of the use of fertilizers and pesticides, which is due to the ability to stimulate the growth of plants by nitrogen-fixation and production of phytohormones, such as indole-3-acetic acid (IAA). The objective of this study was to verify the potential of plant growth promotion of 25 wild isolates from the Agricultural Microbiology Culture Collection of the Federal University of Lavras (CCMA-UFLA) through the evaluation of the biological nitrogen-fixation capacity and the production of IAA. In addition, the growth of three selected strains inoculated on roots of strawberry seedlings in greenhouse conditions was evaluated. The experiment was conducted in a completely randomized design (CRD), with an 8 × 2 factorial schemes involving eight combinations of bacteria: alone, in pairs and threes, plus the control without inoculation. Two fertilizer levels were used (0% and 50% of nitrogen), totaling 16 treatments with eight replicates each. After 75 days, variables such as root length, root dry weight, aerial part length, aerial part dry weight, leaf number, total dry mass and ultrastructural analysis of the inoculated and uninoculated roots, were evaluated. The results showed that the strawberry crop responded positively to inoculation with the three bacteria combined Azospirillum brasilense (Ab-V5) + Burkholderia cepacia (CCMA 0056) + Enterobacter cloacae (CCMA 1285) compared to the uninoculated controls. More expressive responses in terms of plant growth were observed in relation to the combined inoculation of the three bacterial strains plus fertilizer application with 50% of nitrogen.
Assuntos
Fenômenos Fisiológicos Bacterianos , Fragaria/crescimento & desenvolvimento , Fragaria/microbiologia , Fixação de Nitrogênio , Desenvolvimento Vegetal , Azospirillum brasilense/fisiologia , Bactérias/classificação , Bactérias/crescimento & desenvolvimento , Bactérias/isolamento & purificação , Bactérias/metabolismo , Biomassa , Burkholderia cepacia/fisiologia , Enterobacter cloacae , Ácidos Indolacéticos/metabolismo , Nitrogênio , Reguladores de Crescimento de Plantas/metabolismo , Folhas de Planta/microbiologia , Raízes de Plantas/microbiologia , PlântulaRESUMO
BACKGROUND: Burkholderia cenocepacia, an opportunistic pathogen that causes lung infections in cystic fibrosis (CF) patients, is associated with rapid and usually fatal lung deterioration due to necrotizing pneumonia and sepsis, a condition known as cepacia syndrome. The key bacterial determinants associated with this poor clinical outcome in CF patients are not clear. In this study, the cytotoxicity and procoagulant activity of B. cenocepacia from the ET-12 lineage, that has been linked to the cepacia syndrome, and four clinical isolates recovered from CF patients with mild clinical courses were analysed in both in vitro and in vivo assays. METHODS: B. cenocepacia-infected BEAS-2B epithelial respiratory cells were used to investigate the bacterial cytotoxicity assessed by the flow cytometric detection of cell staining with propidium iodide. Bacteria-induced procoagulant activity in cell cultures was assessed by a colorimetric assay and by the flow cytometric detection of tissue factor (TF)-bearing microparticles in cell culture supernatants. Bronchoalveolar lavage fluids (BALF) from intratracheally infected mice were assessed for bacterial proinflammatory and procoagulant activities as well as for bacterial cytotoxicity, by the detection of released lactate dehydrogenase. RESULTS: ET-12 was significantly more cytotoxic to cell cultures but clinical isolates Cl-2, Cl-3 and Cl-4 exhibited also a cytotoxic profile. ET-12 and CI-2 were similarly able to generate a TF-dependent procoagulant environment in cell culture supernatant and to enhance the release of TF-bearing microparticles from infected cells. In the in vivo assay, all bacterial isolates disseminated from the mice lungs, but Cl-2 and Cl-4 exhibited the highest rates of recovery from mice livers. Interestingly, Cl-2 and Cl-4, together with ET-12, exhibited the highest cytotoxicity. All bacteria were similarly capable of generating a procoagulant and inflammatory environment in animal lungs. CONCLUSION: B. cenocepacia were shown to exhibit cytotoxic and procoagulant activities potentially implicated in bacterial dissemination into the circulation and acute pulmonary decline detected in susceptible CF patients. Improved understanding of the mechanisms accounting for B. cenocepacia-induced clinical decline has the potential to indicate novel therapeutic strategies to be included in the care B. cenocepacia-infected patients.
Assuntos
Lesão Pulmonar Aguda/microbiologia , Lesão Pulmonar Aguda/fisiopatologia , Burkholderia cepacia/classificação , Burkholderia cepacia/fisiologia , Pulmão/microbiologia , Infecções Respiratórias/microbiologia , Infecções Respiratórias/fisiopatologia , Lesão Pulmonar Aguda/etiologia , Animais , Infecções por Burkholderia/complicações , Infecções por Burkholderia/microbiologia , Infecções por Burkholderia/fisiopatologia , Feminino , Camundongos , Especificidade da EspécieRESUMO
Burkholderia (Pseudomonas) cepacia is a plant growth promoting rhizobacteria that could improve maize productivity. In this work we studied some properties of B. cepacia strain 0057 in relation to interaction with maize. Spermosphere effect, chemostatic response, indolic compounds and siderophores production were evaluated. We observed inhibitory effect on bacterial growth by maize seeds and their soluble extracts. Root exudates had positive chemiostatic effect. We founded indolic compounds production (20.1 micrograms/ml) and siderophore presence. We think that this microorganisms could improve maize production.