The Regulatory RNA Confers a Potential Selective Advantage to for Intestinal Colonization.

The aim of this study was to evaluate the role of the regulatory small RNA (sRNA) Ern0160 in gastrointestinal tract (GIT) colonization by . For this purpose, four strains of were used, Aus0004 (WT), an -deleted Aus0004 mutant (Δ0160), a -complemented Δ0160 strain overexpressing (Δ0160_0160), and a strain Δ0160 with an empty pAT29 vector (Δ0160_pAT29). Strains were studied both and , alone and in competitive assays. In experiments, no difference was observed between WT and Δ0160 strains cultured single while Δ0160_0160 strain grew more slowly than Δ0160_pAT29. In competitive assays, the WT strain was predominant compared to the deleted strain Δ0160 at the end of the experiment. Then, experiments were performed using a GIT colonization mouse model. Several existing models of GIT colonization were compared while a novel one, combining ceftriaxone and amoxicillin, was developed. A GIT colonization was performed with each strain alone, and no significant difference was noticed. By contrast, significant results were obtained with co-colonization experiments. With WT + Δ0160 suspension, a significant advantage for the WT strain was observed from day 5 to the end of the protocol, suggesting the involvement of 0160 in GIT colonization. With Δ0160_0160 + Δ0160_pAT29 suspension, the strain with the empty vector took the advantage from day 3 to the end of the protocol, suggesting a deleterious effect of overexpression. Altogether, these findings demonstrate the potential implication of Ern0160 in GIT colonization of . Further investigations are needed for the identification of sRNA target(s) in order to decipher underlying molecular mechanisms.