RESUMO
The present study explores the potential of rhizobacteria isolated from Baccharis linearis and Solidago chilensis in metal(loid)-contaminated soil for producing N-acyl-homoserine lactones (AHLs)-type signal molecules and promoting plant growth. A total of 42 strains were isolated, four demonstrating the production of AHL-type signal molecules. Based on 16S rRNA gene sequencing analyses and MALDI-TOF analyses, these four isolates were identified as belonging to the Pseudomonas genus, specifically P. brassicacearum, P. frederickberguensis, P. koreensis, and P. orientalis. The four AHL-producing strains were evaluated for metal(loid)s tolerance, their plant growth promotion traits, AHL quantification, and their impact on in vitro Lactuca sativa plant growth. The study found that four strains exhibited high tolerance to metal(loid)s, particularly As, Cu, and Zn. Additionally, plant growth-promoting traits were detected in AHL-producing bacteria, such as siderophore production, ammonia production, ACC deaminase activity, and P solubilization. Notably, AHL production varied among strains isolated from B. linearis, where C7-HSL and C9-HSL signal molecules were detected, and S. chilensis, where only C7-HSL signal molecules were observed. In the presence of copper, the production of C7-HSL and C9-HSL significantly decreased in B. linearis isolates, while in S. chilensis isolates, C7-HSL production was inhibited. Further, when these strains were inoculated on lettuce seeds and in vitro plants, a significant increase in germination and plant growth was observed. Mainly, the inoculation of P. brassicacearum and P. frederickberguensis led to extensive root hair development, significantly increasing length and root dry weight. Our results demonstrate that rhizospheric strains produce AHL molecules and stimulate plant growth, primarily through root development. However, the presence of copper reduces the production of these molecules, potentially affecting the root development of non-metalloid tolerant plants such as S. chilensis, which would explain its low population in this hostile environment.
Assuntos
Acil-Butirolactonas , Percepção de Quorum , Percepção de Quorum/genética , Cobre , RNA Ribossômico 16S/genética , Plantas/genética , SoloRESUMO
The microbiological interactions of the roots of non-photosynthetic plants in South America have been scarcely explored. This study analyzes culturable fungal diversity associated with the mycoheterotrophic plant Arachnitis uniflora Phil. (Corsiaceae) in southern Chile, growing in two different understoreys of native (Nothofagus-dominated) and mixed forest (native, Cupressus sempervirens, and Pinus radiata). Rhizospheric and endophytic fungi were isolated, cultured, and purified to identify microorganisms associated with A. uniflora roots. We showed the different fungi associated with the plant, and that these distributions are influenced by the sampling site. We isolated 410 fungal strains (144 endophytic and 266 from the rhizosphere). We identified 13 operative taxonomical units from plants sampled in the mixed forest, while 15 were from the native forest. Rhizospheric microorganisms were mainly related to Penicillium spp., whereas some pathogenic and saprophytic strains were more frequent inside the roots. Our results have also shown that the fungal strains are weak for phosphate solubilization, but other pathways such as organic acid exudation and indole acetic acid production can be considered as major mechanisms to stimulate plant growth. Our results point to new fungal associates of A. uniflora plants reported in Andean ecosystems, identifying new beneficial endophytic fungi associated with roots of this fully mycoheterotrophic plant.
RESUMO
The endophytic strain Chaetomium cupreum isolated from metal-contaminated soil was inoculated in Eucalyptus globulus roots to identify genes involved in metal stress response and plant growth promotion. We analyzed the transcriptome of E. globulus roots inoculated with C. cupreum. De novo sequencing, assembly, and analysis were performed to identify molecular mechanisms involved in metal stress tolerance and plant growth promotion. A total of 393,371,743 paired-end reads were assembled into 135,155 putative transcripts. It was found that 663 genes significantly changed their expression in the presence of treatment, of which 369 were up-regulated and 294 were down-regulated. We found differentially expressed genes (DEGs) encoding metal transporters, transcription factors, stress and defense response proteins, as well as DEGs involved in auxin biosynthesis and metabolism. Our results showed that the inoculation of C. cupreum enhanced tolerance to metals and growth promotion on E. globulus. This study provides new information to understand molecular mechanisms involved in plant-microbe interactions under metals stress.
RESUMO
In soils multi-contaminated with heavy metal and metalloids, the establishment of plant species is often hampered due to toxicity. This may be overcome through the inoculation of beneficial soil microorganisms. In this study, two arsenic-resistant bacterial isolates, classified as Pseudomonas gessardii and Brevundimonas intermedia, and two arsenic-resistant fungi, classified as Fimetariella rabenhortii and Hormonema viticola, were isolated from contaminated soil from the Puchuncaví valley (Chile). Their ability to produce indoleacetic acid and siderophores and mediate phosphate solubilization as plant growth-promoting properties were evaluated, as well as levels of arsenic resistance. A real time PCR applied to Triticum aestivum that grew in soil inoculated with the bacterial and fungal isolates was performed to observe differences in the relative expression of heavy metal stress defense genes. The minimum inhibitory concentration of the bacterial strains to arsenate was up to 7000 mg·L-1 and that of the fungal strains was up to 2500 mg·L-1. P. gessardi was able to produce siderophores and solubilize phosphate; meanwhile, B. intermedia and both fungi produced indoleacetic acid. Plant dry biomass was increased and the relative expression of plant metallothionein, superoxide dismutase, ascorbate peroxidase and phytochelatin synthase genes were overexpressed when P. gessardii plus B. intermedia were inoculated.
RESUMO
Los niños con enfermedades oncológicas en tratamiento convencional se ven afectados tanto emocional como físicamente por la medicina tradicional y, considerando, que la OMS ha realizado publicaciones en que se invita a los países a implementar el uso de terapias complementarias, y que el Ministerio de Salud del Gobierno de Chile ha reconocido a la acupuntura, naturopatía y homeopatía como profesiones auxiliares de salud, se realizó una investigación descriptiva, basada en la metodología cuantitativa y tomando como referencia la Teoría de los Seres Unitarios planteada por Martha Rogers, con el propósito de conocer el impacto que producen las terapias complementarias en la tolerancia al tratamiento convencional, y la participación del Profesional de Enfermería en su uso. El proceso de recolección de datos fue durante el mes de diciembre de 2014 a enero de 2015, en los Hospitales Dr. Exequiel González Cortés y Dr. Roberto del Río, en el Hospital Clínico de la Universidad Católica de Chile, en la Clínica Dávila y en la Fundación Nuestros Hijos, sede San Miguel. Se encuestó a 120 cuidadores de niños con enfermedades oncológicas, quienes voluntariamente respondieron un cuestionario autoadministrado. Al cuantificar el uso de terapias complementarias, se determinó que 56 niños (47%), utilizan este tipo de terapias y que a su vez, más de la mitad de quienes la utilizan, hacen uso de más de un tipo de éstas. Al determinar el impacto de las terapias complementarias en la tolerancia al tratamiento convencional el resultado fue de carácter positivo, con un porcentaje que fluctúa entre un 75% y un 97%. Finalmente, al establecer el grado de participación de los Profesionales de Enfermería en el uso de terapias complementarias, se evidenció que su participación es baja (18%).