| Congresso Brasileiro de Microbiologia 2023 | Resumo: 758-2 | ||||
Resumo:The western region of the Brazilian state of Bahia has a climate characterized as hot and dry, with concentrated rainfall and a wide temperature range. The soils have sandy textures and are naturally poor in terms of fertility. Paspalum notatum is a rustic perennial grass species of great economic importance in several countries, used as native and cultivated pasture and as permanent vegetation cover of soil surfaces. The rhizospheric region of native and cultivated plants in extremophile environments harbors a microbial diversity adapted to high salinity and temperature conditions and the unavailability of water resources. Therefore, obtaining isolates from these environments and testing them as plant growth promoters (PGP) expands the research for biotechnological tools for agricultural improvements aiming for yield increase,
expansion of arable areas, and optimization of available resources. This study aimed to isolate, identify, and bioprospecting cultivable rhizospheric bacteria associated with the P. notatum rhizosphere in terms of potential for promoting plant growth. The isolations were made in selective culture media (Sperber and TBA), and the molecular identification was by partial sequencing of the 16S rRNA gene. Afterward, the isolates were evaluated for plant growth promotion by organic and inorganic phosphorus (P) solubilization tests in Fitato and Pikovskaya media, respectively, exopolysaccharide (EPS) production, biofilm formation, and indole-acetic acid synthesis (IAA). Eight selected isolates were identified, being 3 Bacillus sp. (SGBT-9, TGBT-5, and TGBT-13), 3 Pseudomonas sp. (SGBT-8, TGBT-15, and TGBT-17), 1 Lysinibacillus sp. (SGBT-4) and 1 Paenibacillus sp. (TGBT-16). Concerning P solubilization, the isolates were classified according to the solubilization index (IS - ratio between solubilization halo and colony diameter). Regarding biofilm formation, they were classified as non-formers, weakly forming, moderately forming, and strongly forming based on the colorimetric method. Six of the eight isolates showed solubilization rates ranging from 1.0 to 2.1 in the Phytate medium and 1.0 to 1.2 in the Pikovskaya medium. The isolate of Bacillus TBT-13 stood out with the highest IS in the two P sources. Five isolates (SGBT-9, SGBT-4, SGBT-8, TGBT-15 and TGBT-17) showed EPS formation. Bacterium Pseudomonas stood out in biofilm formation, with values between 3.9 and 4.2 and classifying these as moderately and strongly biofilm forming; two Bacillus isolates also stand out that showed moderate formation, with values between 2.5 and 2.8. The isolates SGBT-4, SGBT-9, and TGBT-5 showed the highest AIA synthesis, with values of 11.38μg.mL-1, 11.15μg.mL-1 and 6.81μg.mL-1, respectively. The other isolates were not able to synthesize AIA. It was concluded that the bacteria isolated from the rhizosphere of P. notatum grown in sandy soils in the western region of Bahia showed characteristics of PGR, thus, promising candidates for studies as plant inoculants and production of bioformulation.
Palavras-chave: Bacterial Isolation, Extremophiles, Plant Growth Promoter Agência de fomento:Faped - Fundação de Apoia a Pesquisa e ao Desenvolvimento | |||||