Evidence for ferritin as dominant iron-bearing species in the rhizobacterium Azospirillum brasilense Sp7 provided by low-temperature/in-field Mössbauer spectroscopy
- 293 Downloads
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 57FeIII 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.
KeywordsIron metabolism Bacterial ferritin Azospirillum brasilense 57Fe transmission Mössbauer spectroscopy
This study was supported in parts by Project LO1305 of the Ministry of Education, Youth and Sports of the Czech Republic and by The Russian Foundation for Basic Research (Grant No. 13-04-01538-a), as well as under the Agreement on Scientific Cooperation between the Russian and Hungarian Academies of Sciences for 2011–2013 (Projects Nos. 28 and 29).
Compliance with ethical standards
Conflict of interest
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
- 2.Wisniewski-Dyé F, Drogue B, Borland S, Prigent-Combaret C. Azospirillum-plant interaction: from root colonisation to plant growth promotion. In: Belén Rodelas González M, González-López J, editors. Beneficial plant-microbial interactions: ecology and applications, vol. Chapter 11. Boca Raton: CRC Press; 2013. p. 237–69.CrossRefGoogle Scholar
- 5.Rothballer M, Schmid M, Hartmann A. In situ localization and PGPR-effect of Azospirillum brasilense strains colonizing roots of different wheat varieties. Symbiosis. 2003;34:261–79.Google Scholar
- 14.Bachhawat AK, Ghosh S. Iron transport in Azospirillum brasilense: role of the siderophore spirilobactin. J Gen Microbiol. 1987;133:1759–65.Google Scholar
- 15.Mori E, Fulchieri M, Indorato C, Fani R, Bazzicalupo M. Cloning, nucleotide sequencing, and expression of the Azospirillum brasilense lon gene: involvement in iron uptake. J Bacteriol. 1996;178(12):3440–6.Google Scholar
- 16.Kamnev AA, Renou-Gonnord M-F, Antonyuk LP, Colina M, Chernyshev AV, Frolov I, et al. Spectroscopic characterization of the uptake of essential and xenobiotic metal cations in cells of the soil bacterium Azospirillum brasilense. IUBMB Life. 1997;41:123–30. doi: 10.1080/15216549700201121.CrossRefGoogle Scholar
- 17.Kamnev AA, Tugarova AV, Kovács K, Kuzmann E, Homonnay Z, Kulikov LA, et al. Mössbauer spectroscopic study of iron and cobalt metabolic transformations in cells of the bacterium Azospirillum brasilense Sp7. Bull Russ Acad Sci Phys. 2015;79(8):1036–40. doi: 10.3103/S1062873815080110.CrossRefGoogle Scholar
- 19.Alenkina IV, Oshtrakh MI, Tugarova AV, Biró B, Semionkin VA, Kamnev AA. Study of the rhizobacterium Azospirillum brasilense Sp245 using Mössbauer spectroscopy with a high velocity resolution: Implication for the analysis of ferritin-like iron cores. J Mol Struct. 2014;1073:181–6.CrossRefGoogle Scholar
- 26.Naumann D. Infrared spectroscopy in microbiology. In: Meyers RA, editor. Encyclopedia of analytical chemistry. Chichester: Wiley; 2000. p. 102–31.Google Scholar
- 33.Papaefthymiou GC. The Mössbauer and magnetic properties of ferritin cores. Biochim Biophys Acta. 1800;2010:886–97.Google Scholar
- 35.Alenkina IV, Oshtrakh MI, Klepova YuV, Dubiel SM, Sadovnikov NV, Semionkin VA. Comparative study of the iron cores in human liver ferritin, its pharmaceutical models and ferritin in chicken liver and spleen tissues using Mössbauer spectroscopy with a high velocity resolution. Spectrochim Acta Part A: Mol Biomol Spectrosc. 2013;100:88–93.CrossRefGoogle Scholar
- 36.Kamnev AA, Kovács K, Alenkina IV, Oshtrakh MI. Mössbauer spectroscopy in biological and biomedical research. In: Sharma VK, Klingelhöfer G, Nishida T, editors. Mössbauer spectroscopy: applications in chemistry, biology, and nanotechnology, vol. Chapter 13. N.Y: Wiley; 2013. p. 272–91.CrossRefGoogle Scholar