Citrate-mediated iron uptake in Pseudomonas aeruginosa: involvement of the citrate-inducible FecA receptor and the FeoB ferrous iron transporter
Citrate-mediated iron uptake in Pseudomonas aeruginosa: involvement of the citrate-inducible FecA receptor and the FeoB ferrous iron transporter
复制标题
DOI：
10.1099/mic.0.023531-0
复制
发表时间：
2009-01-01
期刊：
影响因子：
2.8
通讯作者：
Poole, Keith
中科院分区：
文献类型：
--
作者：
Marshall, Bryan;Stintzi, Alain;Poole, Keith
为了鉴定铜绿假单胞菌柠檬酸铁摄取系统的组成部分，构建了铁载体缺陷型菌株（IA 614）的突变体库，并筛选了柠檬酸盐促进的铁限制性培养基中生长的缺陷。突变体破坏基因PA 3901，编码的外膜柠檬酸铁受体，FecA，大肠杆菌（FecA（E. C））的同源物，被回收，并显示缺乏柠檬酸盐促进的生长和柠檬酸盐介导的铁吸收。突变体破坏基因PA 4825，编码同源的MgtA/MgtB镁2+转运蛋白在沙门氏菌肠，同样缺乏柠檬酸盐促进的生长，虽然这是由于柠檬酸盐敏感性的突变体显然从柠檬酸盐促进收购的Fe 2+和由此产生的氧化应激。与柠檬酸盐将Fe以Fe 2+形式递送至细胞一致，缺乏FeoB Fe 2+转运蛋白同源物的铜绿假单胞菌突变体PA 4358在Fe限制培养基中因柠檬酸盐促进的生长而受损，并显示柠檬酸盐介导的Fe摄取显著降低。随后在feoB突变体中消除两种Fe 3+转运蛋白同源物PA 5216和PA 4687，未能进一步损害柠檬酸盐促进的生长或Fe吸收，尽管编码与Fe 2+获取有关的周质铁氧化酶的pcoA的额外损失完全消除了柠檬酸盐介导的Fe吸收。然而，由其他铁载体（例如绿脓菌荧光素）介导的Fe获取在四重敲除菌株中不受影响。这些数据表明，由柠檬酸盐递送至铜绿假单胞菌的Fe在其经由Fe转运组分转运至细胞中之前以Fe 2+形式释放，可能在周质中。
In an attempt to identify components of a ferric citrate uptake system in Pseudomonas aeruginosa, a mutant library of a siderophore-deficient strain (IA614) was constructed and screened for defects in citrate-promoted growth in an Fe-restricted medium. A mutant disrupted in gene PA3901, encoding a homologue of the outer-membrane ferric citrate receptor, FecA, of Escherichia coli (FecA(E.c)), was recovered and shown to be deficient in citrate-promoted growth and citrate-mediated Fe uptake. A mutant disrupted in gene PA4825, encoding a homologue of the MgtA/MgtB Mg2+ transporters in Salmonella enterica, was similarly deficient in citrate-promoted growth, though this was due to a citrate sensitivity of the mutant apparently resulting from citrate-promoted acquisition of Fe2+ and resultant oxidative stress. Consistent with citrate delivering Fe to cells as Fe2+, a P. aeruginosa mutant lacking the FeoB Fe2+ transporter homologue, PA4358, was compromised for citrate-promoted growth in Fe-restricted medium and showed markedly reduced citrate-mediated Fe uptake. Subsequent elimination of two Fe3+ transporter homologues, PA5216 and PA4687, in the feoB mutant failed to further compromise citrate-promoted growth or Fe uptake, though the additional loss of pcoA, encoding a periplasmic ferroxidase implicated in Fe2+ acquisition, completely abrogated citrate-mediated Fe uptake. Fe acquisition mediated by other siderophores (e.g. pyoverdine) was, however, unaffected in the quadruple knockout strain. These data indicate that Fe delivered to P. aeruginosa by citrate is released as Fe2+, probably in the periplasm, prior to its transport into cells via Fe transport components.