Extração, purificação e caracterização de substância antagonista produzida por Shigella sonnei

Abstract

Shigella is associated with the etiopathogenesis of shigellosis a severe type of inflammatory diarrhea responsible for high morbidity and mortality rates mainly among children aged less than five years. While S. sonnei is the predominant species in developed areas S. flexneri is frequently found in underdeveloped regions. Several bacteria are able to produce bacteriocins proteinaceous substances that exhibit activity especially against taxonomically related strains. Bacteriocin production seems to represent a competitive advantage against organisms that share the same habitat. The production of bacteriocins by S. sonnei strains isolated from fecal specimens of children with diarrhea in Belo Horizonte has already been reported. We aimed to extract, purify, and partially characterize antagonistic substance(s) synthesized by a S. sonnei isolate. Following protein precipitation by employing ammonium sulfate the intracellular fraction obtained at 75% salt saturation was submitted to purification by sequential steps of liquid chromatography ionic exchange, gel filtration, and reverse phase. Fractions collected from the last purification step were submitted to mass spectrometry. Substances with several molecular masses ranging from 5 to 10 kDa were detected,suggesting the possibility that antagonistic substance(s) should be microcin(s).