The Bradyrhizobium japonicum exporter ExsFGH is involved in efflux of ferric xenosiderophores from the periplasm.

Autor: Ong A; Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, The University at Buffalo, Buffalo, New York, United States of America., O'Brian MR; Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, The University at Buffalo, Buffalo, New York, United States of America.
Jazyk: angličtina
Zdroj: PloS one [PLoS One] 2024 Jan 02; Vol. 19 (1), pp. e0296306. Date of Electronic Publication: 2024 Jan 02 (Print Publication: 2024).
DOI: 10.1371/journal.pone.0296306
Abstrakt: The gram-negative bacterium Bradyrhizobium japonicum can take up structurally dissimilar ferric siderophores from the environment (xenosiderophores) to meet its nutritional iron requirements. Siderophore-bound iron transported into the periplasm is reduced to the ferrous form by FsrB, dissociated from the siderophore and the free ion is then transported into the cytoplasm by the ferrous iron transporter FeoAB. Here, we identified the RND family exporter genes exsFG and exsH in a selection for secondary site suppressor mutants that restore growth of an fsrB mutant on the siderophores ferrichrome or ferrioxamine. The low level of radiolabel accumulation from 55Fe-labeled ferrichrome or ferrioxamine observed in the fsrB mutant was restored to wild type levels in the fsrB exsG mutant. Moreover, the exsG mutant accumulated more radiolabel from the 55Fe-labeled siderophores than the wild type, but radiolabel accumulation from inorganic 55Fe was similar in the two strains. Thus, ExsFGH exports siderophore-bound iron, but not inorganic iron. The rescued fsrB exsG mutant required feoB for growth, indicating that ExsFGH acts on those siderophores in the periplasm. The exsG mutant was more sensitive to the siderophore antibiotic albomycin than the wild type, whereas the fsrB mutant was more resistant. This suggests ExsFGH normally exports ferrated albomycin. B. japonicum is naturally resistant to many antibiotics. The exsG strain was very sensitive to tetracycline, but not to six other antibiotics tested. We conclude that ExsFGH is a broad substrate exporter that is needed to maintain siderophore homeostasis in the periplasm.
Competing Interests: The authors have declared that no competing interests exist.
(Copyright: © 2024 Ong, O’Brian. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)
Databáze: MEDLINE
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