title: Evidence for ferritin as dominant iron-bearing species in the rhizobacterium Azospirillum brasilense Sp7 provided by low-temperature/in-field Mössbauer spectroscopy.
abstract: For the ubiquitous diazotrophic rhizobacterium Azospirillum brasilense, which has been attracting the attention of researchers worldwide for the last 35 years owing to its significant agrobiotechnological and phytostimulating potential, the data on iron acquisition and its chemical speciation in cells are scarce. In this work, for the first time for azospirilla, low-temperature (at 80 K, 5 K, as well as at 2 K without and with an external magnetic field of 5 T) transmission Mössbauer spectroscopic studies were performed for lyophilised biomass of A. brasilense (wild-type strain Sp7 grown with (57)Fe(III) nitrilotriacetate complex as the sole source of iron) to enable quantitative chemical speciation analysis of the intracellular iron. In the Mössbauer spectrum at 80 K, a broadened quadrupole doublet of high-spin iron(III) was observed with a few percent of a high-spin iron(II) contribution. In the spectrum measured at 5 K, a dominant magnetically split component appeared with the parameters typical of ferritin species from other bacteria, together with a quadrupole doublet of a superparamagnetic iron(III) component and a similarly small contribution from the high-spin iron(II) component. The Mössbauer spectra recorded at 2 K (with or without a 5 T external field) confirmed the assignment of ferritin species. About 20% of total Fe in the dry cells of A. brasilense strain Sp7 were present in iron(III) forms superparamagnetic at both 5 and 2 K, i.e. either different from ferritin cores or as ferritin components with very small particle sizes.
authors.affiliation: Institute of Chemistry, Eötvös Loránd University, P.O. Box 32, Budapest, 1512, Hungary.
authors.forename: Krisztina
authors.initials: K
authors.lastname: Kovács
authors.affiliation: Institute of Biochemistry and Physiology of Plants and Microorganisms, Russian Academy of Sciences, Saratov, 410049, Russia. aakamnev@ibppm.sgu.ru.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Kamnev
authors.affiliation: Regional Centre of Advanced Technologies and Materials, Departments of Experimental Physics and Physical Chemistry, Faculty of Science, Palacký University in Olomouc, Olomouc, 771 46, Czech Republic.
authors.forename: Jiří
authors.initials: J
authors.lastname: Pechoušek
authors.affiliation: Institute of Biochemistry and Physiology of Plants and Microorganisms, Russian Academy of Sciences, Saratov, 410049, Russia.
authors.forename: Anna V
authors.initials: AV
authors.lastname: Tugarova
authors.affiliation: Institute of Chemistry, Eötvös Loránd University, P.O. Box 32, Budapest, 1512, Hungary.
authors.forename: Ernő
authors.initials: E
authors.lastname: Kuzmann
authors.affiliation: Regional Centre of Advanced Technologies and Materials, Departments of Experimental Physics and Physical Chemistry, Faculty of Science, Palacký University in Olomouc, Olomouc, 771 46, Czech Republic.
authors.forename: Libor
authors.initials: L
authors.lastname: Machala
authors.affiliation: Regional Centre of Advanced Technologies and Materials, Departments of Experimental Physics and Physical Chemistry, Faculty of Science, Palacký University in Olomouc, Olomouc, 771 46, Czech Republic.
authors.forename: Radek
authors.initials: R
authors.lastname: Zbořil
authors.affiliation: Institute of Chemistry, Eötvös Loránd University, P.O. Box 32, Budapest, 1512, Hungary.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Homonnay
authors.affiliation: Centre for Energy Research, Hungarian Academy of Sciences, P.O. Box 49, Budapest, 1525, Hungary.
authors.forename: Károly
authors.initials: K
authors.lastname: Lázár
mesh_terms: D015806:Azospirillum brasilense / Q000737:chemistry / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D005293:Ferritins / Q000737:chemistry / Q000378:metabolism*; D005612:Freeze Drying; D007501:Iron / Q000737:chemistry / Q000378:metabolism*; D060328:Magnetic Phenomena; D017550:Spectroscopy, Fourier Transform Infrared; D015204:Spectroscopy, Mossbauer / Q000379:methods*
chemical_list: D001426:Bacterial Proteins; D005293:Ferritins; D007501:Iron
keywords: 57Fe transmission Mössbauer spectroscopy; Azospirillum brasilense; Bacterial ferritin; Iron metabolism