Seleção e caracterização de potenciais bactérias promotoras do crescimento vegetal e biorremediadoras de petróleo

Abstract

Soil is essential for sustaining life and ecosystem functions; however, contamination by hydrocarbons, due to poor environmental management and petroleum activities, compromises its quality. Remediation strategies, such as phytoremediation associated with bioremediation, have been adopted to mitigate these impacts. This study aimed to select plant growth-promoting (PGP) and petroleum-bioremediating bacteria. A total of 36 isolates from Mimosa oblonga and Erythrina crista-galli, obtained from contaminated areas, were characterized based on their ability to alter the pH of the medium, Gram classification, petroleum degradation capacity, and plant growth promotion in Vigna unguiculata and Phaseolus vulgaris. In this study, strains taxonomically identified as Paraburkholderia sp. P4N5, P6N10, P15N4, and P27N4 promoted greater nodulation in V. unguiculata, whereas Paraburkholderia sp. P12N7, P27N6, P15N4, and Bacillus sp. P7N5 stood out in P. vulgaris. These bacteria include acidifying and alkalinizing microorganisms, both Gram-positive and Gram-negative, capable of tolerating and degrading petroleum in in vitro tests. These isolates were also tested in greenhouse conditions in soils without and with 0.5% petroleum to evaluate plant growth promotion in both species and the degradation capacity of the strains. In P. vulgaris grown in non-contaminated soil, no significant differences were observed in biometric parameters; however, nodulation was reduced in the absence of inoculation and the presence of mineral nitrogen. In V. unguiculata, Paraburkholderia sp. P27N4 was prominent in nodule formation. However, in contaminated soil, Paraburkholderia sp. P15N4 enhanced root volume in P. vulgaris, whereas Paraburkholderia sp. P12N7 promoted greater nodulation. Hydrocarbon degradation was confirmed by gas chromatography-mass spectrometry, with Paraburkholderia sp. P15N4, P27N6, and Rhizobium tropici being the most efficient. Additionally, Paraburkholderia sp. P12N7, P27N4, P27N6, and Bacillus sp. P7N5 produced indole-3-acetic acid in vitro, with the latter two also solubilizing phosphate. The results highlight the ability of these strains to establish symbiosis, promote plant growth, and degrade hydrocarbons, underscoring their potential for application in bioremediation strategies.