The RND protein is involved in the vulnibactin export system in Vibrio vulnificus M2799

• DOI: 10.1016/j.micpath.2014.09.001
• Publication Date: 2014-09-06T16:54:59Z
• Authors: Hiroaki Kawano; Katsushiro Miyamoto; Megumi Yasunobe; Masahiro Murata; Tomoka Myojin; Takahiro Tsuchiya; Tomotaka Tanabe; Tatsuya Funahashi; Takaji Sato; Takashi Azuma; Yoshiki Mino; Hiroshi Tsujibo
• Keywords: DNA, Bacterial; 0303 health sciences; DNA Mutational Analysis; Molecular Sequence Data; Membrane Transport Proteins; Sequence Analysis, DNA; Amides; Culture Media; 03 medical and health sciences; Oxazoles; Vibrio vulnificus; Gene Deletion

Vibrio vulnificus, an opportunistic marine bacterium that causes a serious, often fatal, infection in humans, requires iron for its pathogenesis. This bacterium exports vulnibactin for iron acquisition from the environment. The mechanisms of vulnibactin biosynthesis and ferric-vulnibactin uptake systems have recently been reported, while the vulnibactin export system has not been reported. Mutant growth under low-iron concentration conditions and a bioassay of the culture supernatant indicate that the VV1_0612 protein plays a crucial role in the vulnibactin secretion as a component of the resistance-nodulation-division (RND)-type efflux system in V. vulnificus M2799. To identify which RND protein(s) together with VV1_0612 TolC constituted the RND efflux system for vulnibactin secretion, deletion mutants of 11 RND protein-encoding genes were constructed. The growth inhibition of a multiple mutant (Δ11) of the RND protein-encoding genes was observed 6 h after the beginning of the culture. Furthermore, ΔVV1_1681 exhibited a growth curve that was similar to that of Δ11, while the multiple mutant except ΔVV1_1681 showed the same growth as the wild-type strain. These results indicate that the VV1_1681 protein is involved in the vulnibactin export system of V. vulnificus M2799. This is the first genetic evidence that vulnibactin is secreted through the RND-type efflux systems in V. vulnificus.