Utilization of hemin and hemoglobin by Vibrio vulnificus biotype 2

Abstract

The eel pathogen Vibrio vulnificus biotype 2 is able to use hemoglobin (Hb) and hemin (Hm) to reverse iron limitation. In this stud, the adjuvant effect of both compounds on eel pathogenicity has been evaluated and confirmed. Further, we have studied the heme-iron acquisition mechanism displayed by this bacterium. Whole cells were capable of binding Hb and Hm, independently of (i) iron levels in growth medium and (ii) the presence of polysaccharide capsules on bacterial surface. The Hb- and Hm-binding capacity was retained by the outer membrane protein (OMP) fraction and was abolished after proteolytic digestion of OMP samples. Western blotting (immunoblotting) of denatured OMPs revealed that two major protein bands of 36 and 32 kDa were involved in both Hm and Hb binding. The expression of these proteins was not affected by iron levels. In addition, V. vulnificus biotype 2 produced extracellular proteases, not regulated by iron, that were active against native Hb. In conclusion, the overall data suggest that the eel pathogen V. vulnificus biotype 2 can obtain iron by means of a mechanism which involves a direct interaction between the heme moiety and constitutive OMPs.

Anguibactin‐ versus vanchrobactin‐mediated iron uptake in Vibrio anguillarum: evolution and ecology of a fish pathogen

“…Thus, the utility of haem uptake mechanisms present in all vibrios, including V. anguillarum , V. cholerae , V. parahaemolyticus , V. vulnificus etc. (Fouz et al. , 1996; O'Malley et al.…”

Ferric-reductase activities in Vibrio vulnificus biotypes 1 and 2

“…These systems have been partially characterized: the siderophores produced by biotype 1 strains are mainly of the phenolate type, and the ones from biotype 2 strains are mainly of the hydroxamate type [8]. Moreover, both biotypes produce hemolysins and use hemin and hemoglobin as iron sources [9]. However, nothing is known about the mechanisms of iron reduction before this element is incorporated into cell metabolism.…”

Characterization of a mutant of Vibrio vulnificus for heme utilization

“…Some of hematin‐binding proteins produced by human pathogens are iron repressible [1, 2]. However, in vibrios, such as V. vulnificus biogroup 2 [13] and V. anguillarum [14], efficient hematin adsorption by whole cells was evident even when grown under iron‐replete conditions. Major outer membrane proteins of ∼37 kDa has been demonstrated to be a primary hematin‐binding protein in the vibrios [13, 14].…”

“…However, in vibrios, such as V. vulnificus biogroup 2 [13] and V. anguillarum [14], efficient hematin adsorption by whole cells was evident even when grown under iron‐replete conditions. Major outer membrane proteins of ∼37 kDa has been demonstrated to be a primary hematin‐binding protein in the vibrios [13, 14]. Since V. vulnificus expressed constitutively 38‐kDa major outer membrane protein (Fig.…”