RESUMO
The ability of As-resistant endophytic bacteria in As transformation and plant growth promotion was determined. The endophytes were isolated from As-hyperaccumulator Pteris vittata (PV) after growing for 60 d in a soil containing 200 mg kg(-1) arsenate (AsV). They were isolated in presence of 10 mM AsV from PV roots, stems, and leaflets, representing 4 phyla and 17 genera. All endophytes showed at least one plant growth promoting characteristics including IAA synthesis, siderophore production and P solubilization. The root endophytes had higher P solubilization ability than the leaflet (60.0 vs. 18.3 mg L(-1)). In presence of 10 mM AsV, 6 endophytes had greater growth than the control, suggesting As-stimulated growth. Furthermore, root endophytes were more resistant to AsV while the leaflet endophytes were more tolerant to arsenite (AsIII), which corresponded to the dominant As species in PV tissues. Bacterial As resistance was positively correlated to their ability in AsV reduction but not AsIII oxidation. The roles of those endophytes in promoting plant growth and As resistance in P. vittata warrant further investigation.
Assuntos
Arsênio/análise , Bactérias/isolamento & purificação , Farmacorresistência Bacteriana , Endófitos/isolamento & purificação , Pteris/crescimento & desenvolvimento , Poluentes do Solo/análise , Arseniatos/análise , Arsênio/farmacologia , Arsenitos/análise , Bactérias/crescimento & desenvolvimento , Endófitos/crescimento & desenvolvimento , Oxirredução , Filogenia , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/microbiologia , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/microbiologia , Caules de Planta/efeitos dos fármacos , Caules de Planta/crescimento & desenvolvimento , Caules de Planta/microbiologia , Pteris/efeitos dos fármacos , Pteris/microbiologia , Poluentes do Solo/farmacologiaRESUMO
We isolated and characterized As-resistant endophytic bacteria (AEB) from two arsenic hyperaccumulators. Their plant growth promoting traits and the relation between As tolerance and transformation were evaluated. A total of 41 and 33 AEB were isolated from Pteris vittata (PV) and Pteris multifida (PM) respectively. PV AEB represented 2genera while PM AEB comprised of 12 genera, with Bacillus sp. being the most dominant bacteria from both plants. All AEB had limited ability in solubilizing P and producing indole acetic acid (IAA) and siderophore. All isolates tolerated 10mM arsenate (As(V)), with PV isolates being more tolerant to As(V) and PM more tolerant to arsenite (As(III)). Bacterial arsenic tolerance was related to their ability in As(III) oxidation and As(V) reduction as well as their ability to retain As in the biomass to a varying extent. Though AEB showed limited plant growth promoting traits, they were important in arsenic tolerance and speciation in plants.
