| Congresso Brasileiro de Microbiologia 2023 | Resumo: 212-1 | ||||
Resumo:Within the soil microbial population, mainly in relation to rhizospheric microorganisms (root-soil interface), actinobacteria are important biotic sources for plant growth and development. There is an increasing use of this bacterial phylum for the production of phytohormones, enzymes, siderophores, antibiotics and also for the solubilization of minerals and mobilization of nutrients present in the soil. The semi-arid region of Brazil is a hotspot for these bacteria. Indole acetic acid (IAA) is one of the most physiologically active auxins and a common product of L- tryptophan metabolism produced by several microorganisms including actinobacteria. Thus, considering the
rich biodiversity of the semi-arid region combined with the ability of actinobacteria to produce several metabolites, the main goal of this study was to validate the hypothesis that actinobacteria from the semi-arid region are potential producers of indoleacetic acid. We used 35 actinobacteria strains originated from the culture collection of the Laboratory of Environmental Microbiology (LAMAB) of the Federal University of Ceará. To quantify IAA production, we used the method proposed by Bric et al. (1991) combined with the quantitative method of Husen (2003). We also modified the culture medium supplementing it with tryptophan. The liquid culture medium used was Luria Bertani (LB). 1.5 mL of culture medium was added in microtubes, which were centrifuged at 9500 x g for 2 minutes. Then, 750 μL of supernatant was transferred to 1.5 mL microtubes and 750 μL of Salkwoski reagent. The absorbances were read at 530 nm, half an hour after the addition of the colored reagent, and to obtain the standard curve, indolyl acetic acid with commercial IAA was used. The strains were classified according to IAA production in low
production (<1μg. mL-1); medium production (1-10 μg. mL-1); high production (11-50 μg. mL-1) and high production (>51 μg. mL-1). The quantitative data, obtained from the IAA concentration calculations, were submitted to the normality test and subsequently submitted to analysis of variance (ANOVA) (p < 0.05), using the PAST Program. All bacteria strains were able to produce IAA. Seven strains were classified as low production and 28 were framed with a medium production of the phytohormone. Strains UBJ 17 and UBJ27 reached the highest values of 5.95 μg.mL-1 and 6.37 μg.mL-1; the lowest values were those of UBJ 08 with 0.54 μg.mL-1 and UBJ 29 0.75 μg.mL-1. The factor that explains the absorbance values obtained is explained by the non-standardization of the inoculum, thus, the values vary between isolates and treatments. A possible future alternative would be the use of spore suspension, where precise control over the amount of inoculum can be maintained. Despite this, our data reveal the biotechnological potential of actinobacteria isolates to be used in the development of biofertilizers. Palavras-chave: Actinobacteria, Biotechnological Potential, IAA, Secondary Metabolites Agência de fomento:Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) | |||||