Characterization of Edwardsiella tarda rpoS: effect on serum resistance, chondroitinase activity, biofilm formation, and autoinducer synthetases expression

Abstract

In this study, rpoS gene was identified from Edwardsiella tarda EIB202 and its functional role was analyzed by using an in-frame deletion mutant rpoS and the complemental strain rpoS (+). Compared with the wild type and rpoS (+), rpoS was impaired in terms of the ability to survive under oxidative stress and nutrient starvation, as well as the resistance to 50% serum of Scophthalmus maximus in 3 h, demonstrating essential roles of RpoS in stress adaptation. The rpoS mutant also displayed markedly increased chondroitinase activity and biofilm formation. Real-time polymerase chain reaction revealed that the expression level of quorum sensing autoinducer synthetase genes luxS and edwI was increased by 3.7- and 2.5-fold in the rpoS mutant strain. Those results suggested that rpoS might be involved in the negative or positive regulation of chondroitinase and biofilm formation, or quorum sensing networks in E. tarda, respectively. Although there were no obvious differences between the wild-type and the rpoS mutant in adherence of epithelioma papulosum cyprini (EPC) cell and in the lethality on fish model, rpoS deletion leads to the drastically reduced capacity for E. tarda to internalize in EPC cells, indicating that RpoS was, while not the main, the factor required for the virulence network of E. tarda.

QseBC controls flagellar motility, fimbrial hemagglutination and intracellular virulence in fish pathogen Edwardsiella tarda

“…Construction of complement strain was performed as described by Xiao et al [21]. Briefly, intact gene containing the putative promoter region was amplified and introduced into plasmid pMMBK.…”

Transcriptomic dissection of the horizontally acquired response regulator EsrB reveals its global regulatory roles in the physiological adaptation and activation of T3SS and the cognate effector repertoire inEdwardsiella piscicidaduring infection toward turbot

“…38,57 Healthy turbot weighing 30 § 3 g were acclimatized in an aerated tank for at least 2 weeks with a continuous flow of sand-filtered seawater at 14 »16 C. For characterization of in vivo expression of the putative effectors, 40 fish were intraperitoneal (i.p.) challenged with 100 ml WT or DesrB suspension (10 6 CFU/ml).…”

“…57 Upstream and downstream fragments were generated by PCR using the primer pairs P1/P2 and P3/P4, respectively; the primer sequences are given in Table S3. Overlap PCR with primer pair P1/P4 was used to generate fragments with in-frame deletions.…”

“…2 £ LD 50 ) in 0.1 ml of PBS. 57 Relative percent survival (RPS) was calculated according to the following formula:…”

Comparative proteomic analysis reveals new components of the PhoP regulon and highlights a role for PhoP in the regulation of genes encoding the F1F0 ATP synthase in Edwardsiella tarda

“…A deletion fragment from bp 103 to 1353 in atpD was created in the same way using primer pairs AtpD-A/AtpD-B and AtpD-C/AtpD-D (Table 2). The fused fragments were sequenced and cloned into suicide vector pDMK (Xiao et al, 2009) that was linearized with BglII and SphI. The resulting plasmids, pDMK-aur and pDMK-atpD, were mated from E. coli SM10 lpir into E. tarda EIB202 by conjugation.…”