Riboflavin biosynthesis is associated with assimilatory ferric reduction and iron acquisition by Campylobacter jejuni
Riboflavin biosynthesis is associated with assimilatory ferric reduction and iron acquisition by Campylobacter jejuni
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DOI：
10.1128/aem.01919-07
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发表时间：
2007-12-01
影响因子：
4.4
通讯作者：
Walton, Nicholas J.
中科院分区：
文献类型：
--
作者：
Crossley, Rachel A.;Gaskin, Duncan J. H.;Walton, Nicholas J.
细菌获取必需金属铁的途径之一是将不溶性铁还原为可溶铁，然后将铁转运到细胞质中。在这个鲜为人知的过程中，黄素被认为是电子供体。亚铁的摄取对于重要病原体空肠弯曲杆菌的肠道定植是必不可少的，在低氧条件下可能尤其重要。本研究探讨了空肠C. NCTC11168中核黄素生物合成、铁还原和铁获取之间的联系。通过使ribB核黄素生物合成基因（Cj0572）失活产生核黄素营养不良，所产生的等基因ribB突变体仅在外源核黄素或核黄素前体双乙酰存在时生长，而在下游产物黄素腺嘌呤二核苷酸和黄素单核苷酸存在时不生长。在铁限制条件下，ribB突变体的核黄素摄取不受影响，但在铁充足条件下，野生型菌株和ribB突变体的核黄素摄取都较低。编码空肠空肠铁摄取调节因子的fur基因突变导致核黄素摄取增加，而核黄素摄取不依赖于培养基中的铁含量，这表明fur在调节核黄素转运系统中的作用尚不清楚。最后，铁还原活性与生长培养基中的铁有效性无关，但与野生型菌株相比，ribB突变体的铁还原活性降低，相反，毛皮突变体的铁还原活性增加。综上所述，这些发现证实了空肠梭菌铁获取、核黄素产生和核黄素摄取之间的密切关系。
One of the pathways involved in the acquisition of the essential metal iron by bacteria involves the reduction of insoluble Fe3+ to soluble Fe, followed by transport of Fe to the cytoplasm. Flavins have been implicated as electron donors in this poorly understood process. Ferrous iron uptake is essential for intestinal colonization by the important pathogen Campylobacter jejuni and may be of particular importance under low-oxygen conditions. In this study, the links among riboflavin biosynthesis, ferric reduction, and iron acquisition in C. jejuni NCTC11168 have been investigated. A riboflavin auxotroph was generated by inactivation of the ribB riboflavin biosynthesis gene (Cj0572), and the resulting isogenic ribB mutant only grew in the presence of exogenous riboflavin or the riboflavin precursor diacetyl but not in the presence of the downstream products flavin adenine dinucleotide and flavin mononucleotide. Riboflavin uptake was unaffected in the ribB mutant under iron-limited conditions but was lower in both the wild-type strain and the ribB mutant under iron-replete conditions. Mutation of the fur gene, which encodes an iron uptake regulator of C.jejuni, resulted in an increase in riboflavin uptake which was independent of the iron content of the medium, suggesting a role for Fur in the regulation of the as-yet-unknown riboflavin transport system. Finally, ferric reduction activity was independent of iron availability in the growth medium but was lowered in the ribB mutant compared to the wild-type strain and, conversely, increased in the fur mutant. Taken together, the findings confirm close relationships among iron acquisition, riboflavin production, and riboflavin uptake in C.jejuni.