Fur-Regulated Iron Uptake System of Edwardsiella ictaluri and Its Influence on Pathogenesis and Immunogenicity in the Catfish Host

Abstract

The ability of bacterial pathogens to take up iron from the host during infection is necessary for their multiplication within the host. However, host high-affinity iron binding proteins limit levels of free iron in fluids and tissues. To overcome this deficiency of iron during infection, bacterial pathogens have developed iron uptake systems that are upregulated in the absence of iron, typically tightly controlled by the ferric uptake regulator (Fur) protein. The iron uptake system of Edwardsiella ictaluri, a hostrestricted pathogen of channel catfish (Ictalurus punctatus) and the main pathogen of this fish in aquaculture, is unknown. Here we describe the E. ictaluri Fur protein, the iron uptake machinery controlled by Fur, and the effects of fur gene deletion on virulence and immunogenicity in the fish host. Analysis of the E. ictaluri Fur protein shows that it lacks the N-terminal region found in the majority of pathogen-encoded Fur proteins. However, it is fully functional in regulated genes encoding iron uptake proteins. E. ictaluri grown under iron-limited conditions upregulates an outer membrane protein (HemR) that shows heme-hemoglobin transport activity and is tightly regulated by Fur. In vivo studies showed that an E. ictaluri ⌬fur mutant is attenuated and immune protective in zebrafish (Danio rerio) and catfish (Ictalurus punctatus), triggering systemic immunity. We conclude that an E. ictaluri ⌬fur mutant could be an effective component of an immersion-oral vaccine for the catfish industry.

Mechanisms of intrinsic resistance to antimicrobial peptides of Edwardsiella ictaluri and its influence on fish gut inflammation and virulence

“…The number of PCR cycles was normalized to 28 for semiquantitative RT-PCR. 16S (rrn gene) was used as expression control and fadR was used as single gene expression control (Santander et al, 2012).…”

“…Sarkosyl-insoluble OMPs were obtained as previously described (Santander et al, 2012). The OMPs were normalized to 25 mg ml 21 by using an ND-1000 spectrophotometer (NanoDrop) and separated by 10 % (w/v) SDS-PAGE.…”

Inflammatory Effects of Edwardsiella ictaluri Lipopolysaccharide Modifications in Catfish Gut

“…Sarkosyl-insoluble outer membrane proteins (OMPs) were obtained as previously described (55). The outer membrane proteins were LPS detoxified and normalized to 25 g/l by using a Nanodrop ND-1000 spectrophotometer and separated by 10% (wt/vol) SDS-PAGE for verification.…”

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

“…The iron acquisition system is essential for survival as well as for host colonization by Edwardsiella. 15,37,45,46 Here, many genes associated with iron sequestering and transporters (hemin uptake and siderophore-mediated iron uptake systems) were, interestingly, found to be highly induced under both EsrB and DMEM growth conditions. DMEM is nutrient-depleted, therefore, it is likely that iron transport genes were upregulated to enhance uptake of the Figure 1.…”