We determined the ferrophilic characteristics of Vibrio vulnificus to evaluate the potential usefulness of iron chelation therapy for the prevention

Kim CM, et al. J Korean Med Sci. 2009 Apr;24(2):289-295. http://dx.doi.org/10.3346/jkms.2009.24.2.289

Bacterial swarming constitutes a good in vitro model for surface adherence and colonization, and is accompanied by expressions of virulence factors r

In order to determine whether Pseudomonas aeruginosa alkaline protease AprA is involved in facilitating siderophore-mediated iron-acquisition from human transferrins, we measured bacterial growth, the production of siderophore and AprA, iron-acquisition from transferrins, and the proteolytic cleavage of transferrins in an alkaline minimal medium (pH 8.3) containing human transferrins as an iron source and compared these on a time scale. The growth of P. aeruginosa was found to be stimulated in proportion to the iron-saturation levels of transferrins. AprA production and the proteolytic cleavage of transferrins began concomitantly with siderophore production from the early growth phase when P. aeruginosa was actively growing and consuming most iron for growth. However, the AprA-free, but siderophore-containing, culture ultrafiltrates could also remove iron from transferrin. These results indicate that alkaline protease AprA can facilitate the siderophore-mediated iron-uptake of P. aeruginosa via the proteolytic cleavage of transferrins. However, the proteolytic cleavage by AprA is not essentially required for iron-acquisition from transferrins.

In a previous study, we showed that Vibrio vulnificus is a ferrophilic bacterium that requires high levels of available iron for growth. In the present study, we show that iron stimulates, in an unusual manner, the production of cytolysin-hemolysin (VvhA), the most potent exotoxin produced by V. vulnificus. The vvhA gene possesses a putative ferric uptake regulator (Fur)–binding box in the regulatory region, andvvhA transcription was repressed by iron and de-repressed by fur mutation. However, extracellular secretion of VvhA was conversely increased by iron. Iron increased transcription of pilD which encodes PilD, a component of the type II general secretion system responsible for extracellular VvhA secretion. These results indicate that iron increases extracellular VvhA secretion via the type II general secretion system, although it can repress vvhA transcription via Fur