Characterization of Vibrio parahaemolyticus genes encoding the systems for utilization of enterobactin as a xenosiderophore.
We determined the ability of Vibrio parahaemolyticus to utilize enterobactin (Ent) as a xenosiderophore. Homology searches of the V. parahaemolyticus genomic sequence revealed the presence of genes that are homologous to the V. cholerae ferric Ent utilization genes, which consist of the iron-repressible outer-membrane protein genes irgA and vctA, and the ATP-binding cassette transport system operon vctPDGC. Moreover, the irgB and vctR genes, which encode transcriptional regulators, were also found immediately upstream of irgA and vctA, respectively. Growth assays of V. parahaemolyticus indicated that both irgA and vctA mutants grew well in the presence of Ent under iron-limiting conditions, whereas both the irgA/vctA double mutant and the vctPDGC mutant barely grew under the same conditions. In addition, growth assays of three isogenic tonB mutants demonstrated that the TonB2 system, and to a lesser extent the TonB1 system, can provide energy for both IrgA and VctA to transport ferric Ent. SDS-PAGE analysis showed that expression of both IrgA and VctA was enhanced by the presence of Ent. Complementation of the irgB and vctR mutants with their respective genes resulted in the increased expression of IrgA and VctA, respectively. Finally, reverse transcriptase-quantitative PCR revealed that transcription of the Ent utilization system genes is iron-regulated, and that transcription of irgA and vctA under iron-limiting conditions is further activated by proteins encoded by irgB and vctR, respectively, together with Ent.
College of Pharmaceutical Sciences, Matsuyama University, 4-2 Bunkyo-cho, Matsuyama, Ehime 790-8578, Japan.
Tomotaka
T
Tanabe
College of Pharmaceutical Sciences, Matsuyama University, 4-2 Bunkyo-cho, Matsuyama, Ehime 790-8578, Japan.
Tatsuya
T
Funahashi
Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan.
Keiichi
K
Shiuchi
Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan.
Noriyuki
N
Okajima
Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan.
Hiroshi
H
Nakao
Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan.
Katsushiro
K
Miyamoto
Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan.
Hiroshi
H
Tsujibo
College of Pharmaceutical Sciences, Matsuyama University, 4-2 Bunkyo-cho, Matsuyama, Ehime 790-8578, Japan.
Shigeo
S
Yamamoto
D018528:ATP-Binding Cassette Transporters / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D004758:Enterobactin / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D017262:Siderophores / Q000378:metabolism*; D014736:Vibrio parahaemolyticus / Q000235:genetics / Q000378:metabolism*
D018528:ATP-Binding Cassette Transporters; D001425:Bacterial Outer Membrane Proteins; D017262:Siderophores; D004758:Enterobactin