GENETIC AND BIOCHEMICAL STUDY OF A NOVEL MICROCIN PRODUCED BY A CLINICAL ISOLATE OF Shigella flexneri 2

TORRES LAMBERTI, MF; DIAZ FERNANDEZ, L; PESCARETTI MM,; DELGADO MA,

Congreso; XIII Congreso Argentino de Microbiología General; 2018

SAMIGE

The enterobacterial have the ability to produce antimicrobial peptides called bacteriocins, with the aim to prosper in the host intestine. Shigella is the most common causative agent of diarrhea, an important worldwide health problem. Previously, we report a new low molecular weight bacteriocin (ShpCI172) produced by a Shigella flexneri 2 CI172 strain, which was isolated from fecal sample of a child suffering acute diarrhea. This is the first report where a Shigella flexneri microcin-producer is described, suggesting that the appearance of this strains is not common. The plasmidic profile of this strain suggests that the genetic machinery necessary for the production of ShpCI172 may be encoded in a plasmid. In order to eliminate the harbored plasmids, the CI172 strain was treated by successive culture in LB medium with increasing concentrations of ethidium bromide and subsequent plasmidic profile analysis of the obtained clones. On the other hand, we performed cross-streaking tests to analyze whether the CI172 strain display immunity to other microcin groups. Moreover, the ShpCI172 cell-free supernatant was subjected to a first purification step with ammonium sulfate precipitation and then, to a second purification step with acetone precipitation. Finally, was improved an HPLC analysis. Our results demonstrated that ShpCI172 is a novel antimicrobial peptide of the microcin family, which is encoded by a plasmid allowing it production and purification at large scale.