RESUMO
Siderophore activity was detected in the culture supernatant of the magnetotactic bacterium Magnetospirillum magneticum AMB-1. Here we report the first structural elucidation of a siderophore produced by a magnetotactic bacterium. The structure of the purified compound was 3,4-dihydroxybenzoic acid as determined by nuclear magnetic resonance (NMR) and electro-spray ionization mass spectroscopy (ESI-MS).
Assuntos
Catecóis/análise , Catecóis/metabolismo , Magnetospirillum/metabolismo , Sideróforos/análise , Sideróforos/biossíntese , Quimiotaxia/fisiologia , Espectroscopia de Ressonância Magnética , Magnetismo , Espectrometria de Massas por Ionização por ElectrosprayRESUMO
Iron uptake systems were identified by global expression profiling of Magnetospirillum magneticum AMB-1. feo, tpd, and ftr, which encode ferrous iron transporters, were up-regulated under iron-rich conditions. The concomitant rapid iron uptake and magnetite formation suggest that these uptake systems serve as iron supply lines for magnetosome synthesis.
Assuntos
Perfilação da Expressão Gênica , Regulação Bacteriana da Expressão Gênica , Ferro/farmacologia , Magnetospirillum/genética , Óxido Ferroso-Férrico/metabolismo , Compostos Ferrosos/metabolismo , Genes Bacterianos , Ferro/metabolismo , Magnetospirillum/metabolismo , Proteínas de Membrana Transportadoras/genética , Dados de Sequência Molecular , RNA Bacteriano/análise , RNA Mensageiro/análise , Análise de Sequência de DNARESUMO
A non-magnetic mutant, NMA61, of the magnetic bacterium Magnetospirillum magneticum AMB-1 was generated by transposon mutagenesis to identify genes involved in magnetosome synthesis. The genomic region of NMA61 interrupted by a Mini-Tn5 transposon was analyzed. The transposon was inserted in an open reading frame (ORF) coding for a periplasmic transport binding protein kinase gene homologue. Three adjacent ORFs and a promoter were identified upstream, indicating that the sequences comprised an operon. Phenotype characterizations showed that the growth inhibition imposed by the exogenous non-assimilable iron chelator nitrilotriacetate was relieved in wild type but not in NMA61, by the addition of the isolated wild type siderophore. Higher concentration of siderophores accumulated in the culture medium of NMA61 than in wild type. These data suggest that the interrupted periplasmic transport binding protein kinase gene homologue is required for siderophore transport into M. magneticum AMB-1.
Assuntos
Compostos Férricos/metabolismo , Ferro/farmacocinética , Magnetospirillum/enzimologia , Magnetospirillum/genética , Proteínas Quinases/metabolismo , Sideróforos/metabolismo , Sequência de Aminoácidos , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Magnetospirillum/ultraestrutura , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Mutação , Proteínas Periplásmicas de Ligação/genética , Proteínas Periplásmicas de Ligação/metabolismo , Proteínas Quinases/genética , Proteínas Recombinantes/metabolismo , Homologia de Sequência de Aminoácidos , Sideróforos/genética , Relação Estrutura-AtividadeRESUMO
Siderophore production by the magnetic bacterium Magnetospirillum magneticum AMB-1 is elicited by sufficient iron rather than by iron starvation. In order to clarify this unusual pattern, siderophore production was monitored in parallel to iron assimilation using the chrome azurol sulfonate assay and the ferrozine method respectively. Iron concentration lowered approximately five times less than its initial concentration only within 4 h post-inoculation, rendering the medium iron deficient. A concentration of at least 6 microM Fe(3+) is required to initiate siderophore production. The propensity of M. magneticum AMB-1 for the assimilation of large amounts of iron accounts for the rapid depletion of iron in the medium, thereby triggering siderophore excretion. M. magneticum AMB-1 produces both hydroxamate and catechol siderophores.
