Identificação e avaliação de atividade antimicrobiana de bactéria formadora de endósporo

Abstract

Bioinputs stands out as a sustainable alternative to synthetic pesticides. In this scenario, spore-forming bacteria have relevance because they produce a diversity of antimicrobial bioactives that can be used in the biopesticides formulation. Therefore, the present work aims to identify and characterize a spore-forming bacterium isolated from Cerrado soil and evaluate its antimicrobial properties. The soil isolate was acquired from bacteria collection used in undergraduate courses at the Universidade Federal de Uberlândia on the Patos de Minas campus and cultivated in a non-selective medium. To identify the soil isolate, a polyphasic taxonomy was performed with tests of colony morphology, Gram microscopy, cellular morphology, growth curve (600 nm), antimicrobial characterization by cross-streak method, 16S rRNA Sanger sequencing and phylogenetic analysis using the SILVA and National Center for Biotechnology Information (NCBI) databases. Morphological results identified the soil isolate as a Gram-positive spore-forming bacterium with bacillus morphology and a growth curve lasting 12 hours. Identification by sequencing the 16S rRNA gene was reliable at the level of genus classification as Bacillus, revealing similarity of the soil isolate with the Bacillus cereus complex group of spore-forming bacteria, a clade of extreme difficulty regarding taxonomic characterization at the species level. Phylogenetic analysis corroborated the isolate classification to the group and the antimicrobial test presented a negative result against E. coli, Staphylococcus aureus, Pseudomonas sp., Staphylococcus epidermidis, Enterococcus sp. and Salmonella strains despite the range of antimicrobial compounds produced by the genus reported in the literature. The identification methods used were not sufficient for discrimination of the soil isolate at the species level, requiring a future multifaceted work for better identification.