PHYSIOLOGICAL CHARACTERIZATION OF DIAZOTROPHIC BACTERIA ISOLATED FROM Brachiaria brizantha RHIZOSPHERE

Abstract

The objective of this study was to evaluate the ability of diazotrophic bacteria isolated from Brachiaria brizantha rhizosphere to grow at different pH values and salt concentrations, to produce indoleacetic acid (IAA), and to solubilize phosphate. Both acidity and salinity tolerance tests were performed on modified solid FAM medium. Acidity resistance tests were performed at pH values of 4.0, 5.0, 6.0, and 7.0, while, salt resistance was evaluated at concentrations of 0.01, 5.02, 9.99, 14.96, 19.98, 24.95, 29.98, 34.94, 39.97, 44.94, and 49.96 gL-1 NaCl. For the IAA production assay, bacterial strains were cultivated in liquid DYGS medium both in the absence and presence of tryptophan (Trp). In addition, phosphorus solubilization assay was performed in GL liquid medium. All strains grew at every pH value tested, and a high diversity was observed after salt resistance, IAA production, and phosphate solubilization testing. Strains UNIFENAS 100-51, UNIFENAS 100-52, UNIFENAS 100-60, UNIFENAS 100-63, and UNIFENAS 100-65 were those with the best growth at the highest salt concentrations. Furthermore, in the presence of Trp, strains UNIFENAS 100-63 and UNIFENAS 100-69 were the ones with the highest IAA production. Strain UNIFENAS 100-52 showed the best response to the in vitro phosphate solubilization assay. Based on these results, it can be seen that studies related to the physiological and metabolic characteristics of diazotrophic bacterial strains are important to ensure greater success in the field.

Solubilization of Araxá natural phosphate and decomposition of plant residues by bacterial isolates

“…To evaluate phosphorus solubilization was selected four diazotrophic bacterial strains, two from the Embrapa collection, Ab-V5 (Azospirillum brasilense), and BR 2003 (Bradyrhizobium elkanii), and two isolated from rhizospheric soils of Brachiaria brizantha, UNIFENAS 100-13 (Burkholderia cenocepacia) and UNIFENAS 100-39 (B. cenocepacia). These strains were evaluated for their potential to act as promoters of plant growth by Andrade et al (2019), Terra et al (2019).…”

“…Analyzing the culture medium pH results (Table 2), it appears that the simplest carbohydrates sources promoted a greater reduction of this parameter, which may be related to the production of organic acids (Terra et al, 2019). Papagianni (2007) reports that the production of organic acids can also contribute to the release of other elements, mainly micronutrients present in the rocks, justifying the importance of using rock dust or rock to obtain sustainable agriculture (Brito et al, 2019).…”

“…In recent years, studies have shown that soil microorganisms, through the production of organic acids, can accelerate the release of nutrients from these rocks, increasing availability in the soil solution for plant absorption (Moreira;Siqueira, 2006). Several studies have emphasized the selection of phosphate solubilizing microorganisms (Massenssini et al, 2016;Schueler;Dourado;Rizzo, 2019;Terra et al, 2019), and presented promising data on the potential for application in the field (Dabaja et al, 2019;Souza et al, 2017;Terra et al, 2019). Thus, these microorganisms are biotechnological alternatives that can enable the use of natural phosphate from national deposits, such as Araxá and Catalão natural phosphate.…”

Alelopatia de Brachiaria brizantha cv. Marandu em bactérias promotoras do crescimento vegetal

“…As BPCV são capazes de fixar nitrogênio atmosférico (N2), solubilizar fósforo e potássio, produzir AIA e controlar fitopatógenos (Florentino et al, 2017A;Florentino et al, 2017B;Dias et al, 2019;Terra et al, 2019). No entanto, a sobrevivência e a eficiência para desempenhar esses processos no solo depende de diversos fatores, como a fertilidade, condições climáticas e a espécie vegetal (Moreira et al, 2006).…”

Biotechnological Potential of Soybean Plant Growth-Promoting Rhizobacteria

“…The rhizosphere is a changeable habitat; its composition and structure are affected throughout the vegetative cycle of plants (TERRA et al, 2019). The soil microbial community population varies according to the plant species; moreover, the release of exudates by the root can cause chemical and physical changes in the rhizosphere, which benefits or inhibits microbial growth in this region.…”