RESUMO
Herbaspirillum seropedicae Z67 is a nitrogen-fixing bacterium able to colonize the rhizosphere and the interior of several plants. As iron is a key element for nitrogen fixation, we examined the response of this microorganism to iron deficiency under nitrogen fixing conditions. We identified a H. seropedicae exbD gene that was induced in response to iron limitation and is involved in iron homeostasis. We found that an exbD mutant grown in iron-chelated medium is unable to fix nitrogen. Moreover, we provide evidence that expression of the nifH and nifA genes is iron dependent in a H. seropedicae genetic background.
Assuntos
Proteínas de Bactérias/metabolismo , Herbaspirillum/metabolismo , Ferro/metabolismo , Nitrogenase/metabolismo , Oxirredutases/metabolismo , Fatores de Transcrição/metabolismo , Proteínas de Bactérias/genética , Regulação Bacteriana da Expressão Gênica , Herbaspirillum/enzimologia , Herbaspirillum/genética , Mutação , Fixação de Nitrogênio , Nitrogenase/genética , Oxirredutases/genética , Fatores de Transcrição/genéticaRESUMO
Two transposon-induced mutants of Sinorhizobium meliloti 242 were isolated based on their inability to grow on rich medium supplemented with the metal chelator ethylenediamine di-o-hydroxyphenylacetic acid (EDDHA) and either heme-compounds or siderophores as iron sources. Tagged loci of these mutants were identified as sit B and sit D genes. These genes encode components of an ABC (ATP-binding cassette) metal-type permease in several Gram-negative bacteria. In this work, the phenotypes of these two mutants were compared with those of two siderophore-mediated iron transport mutants. The results strongly implicate a role of the sit genes in manganese acquisition when this metal is limiting in S. meliloti.
