Expressão de antagonismo por Parabacteroides distason: pesquisa, purificação e caracterização de substâncias tipo bacteriocina

Abstract

Parabacteroides distasonis is considered a member of the indigenous microbiota of humans and other animals and has been associated with the etiopathogenesis of several infectious diseases. Bacteriocins are proteinaceous antimicrobial substances synthesized by a wide range of bacteria that play an essential rolein the ecological relationships between bacteria and exhibit a great potential for biotechnological applications. We addressed the production of bacteriocin-like antagonistic substances by P. distasonisand the characterization of one of the substances. A total of 78 isolates obtained from broiler feces were included in the study as test strains. We detected the expression of antagonism by 50% of P. distasonis strains; heteroantagonism, isoantagonism, and autoantagonism were observed. One of the producer strains selected for further steps was submitted to protein extraction. Oxidative stress have led to an increased antagonistic activity of the intracellular fraction precipitated at 50% ammonium sulfate (C50). C50 was inactivated by proteases and high temperatures and kept active after exposure to oganic solvents and a wide pH range. MIC and MBC values demonstrated that C50 acts as a bacteriostatic agent against P. distasonis ATCC 1295. C50 was submitted to sequential steps of chromatography. Data originated from SDS-PAGE and mass spectrometry showed an antagonistic substance of about 7 kDa. Taken together our results indicate the detection of a peptide that exhibits a relatively wide spectrum of activity that possibly plays a relevant ecological role and shows a potential practical application.