El paper dels sistemes toxina-antitoxina tipus II en E.coli LF82

Abstract

Adherent-invasive Escherichia coli (AIEC) is implicated in Crohn's disease, a disorder that

involves chronic inflammation of the gastrointestinal tract. AIEC are able to adhere to and invade

intestinal epithelial cells, survive and replicate in macrophages without causing cell death, and

form persistent cells and intracellular biofilms in the inside macrophages. Toxin-antitoxin (TA)

systems are gene loci widely distributed among bacterial genomes and plasmids that have been

linked to various biological functions in different pathogenic bacteria. The aim of this study is to

investigate the role of type II toxin-antitoxin (TA) systems in the pathogenicity of AIEC from

mutants generated by deletion of selected type II TA systems in the AIEC reference strain LF82.

In previous studies by the group, the possible involvement of the mazEF-1, hipA-2/xre-3 and

relE-1/yiaG-1 systems in the invasion capacity of intestinal epithelial cells of the LF82 strain was

determined. From this point, this work has focused on the characterization of the mutants in

other phenotypic assays. The minimum inhibitory concentration (MIC) has been determined for

LF82 and for the mutants of the TA systems to ciprofloxacin to subsequently perform the

persistent cell formation assay. This persistence assay was performed from exponential phase

cultures and overnight cultures. Subsequently, intracellular replication in macrophages and

motility have been studied.

In the work, an increase in the fraction of persistent cells is observed when starting from the

night culture. In the analysis of intracellular survival in macrophages, a replication index value

of around 400% is obtained, with no differences between the mutants and the LF82 “wild-type”

(WT) strain. Regarding motility, no variation is observed with respect to the LF82 strain.

In this work it has been concluded that TA systems do not seem to play a role in the ability to

form persistent cells, in intracellular replication in macrophages and in motility