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

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

SAN LUIS

Congreso; XIII Congreso Argentino de Microbiología General; 2018

SAMIGE

Enterobacteria have the ability to produce antimicrobial peptides called bacteriocins, which allowed them to thrive host gut. Shigella is the most common causative agent of diarrhea, an important worldwide health problem. Previously, we have reported a new low molecular-weight bacteriocin (ShpCI172) produced by a Shigella flexneri 2 CI172 strain, which was isolated from a fecal sample ofa child suffering acute diarrhea. This was the first report of a microcin-producer Shigella flexneri, suggesting a rare occurrence. The plasmidic profile of this strain suggested that the genetic determinants for the production of ShpCI172 could be encoded in a plasmid. In order to eliminate the harbored plasmids, strain CI172 was successively sub-culture in LB medium containing increasing concentrations of ethidium bromide. After 3 days of treatment, the cultures were plated onto LB medium, for further analysis of plasmidic profiles. We also performed cross-streaking tests to analyze whether the CI172 strain display immunity to other microcin groups. Finally, the ShpCI172 cell-freesupernatant was used to perform a preliminary purification step by ammonium sulfate and/or acetone precipitation, and then subjected to HPLC fractionation. Taking together our results suggest that ShpCI172 would be a novel plasmid-encoded antimicrobial peptide belonging to the microcin family.ShpCI172 is produced and released into the culture medium, facilitating large scale purification for its potential use as an antimicrobial agent.