1. Neutrophilic iron-oxidizing bacteria Sphaerotilus-Leptothrix materials for application in nano and biotechnologies
R. Angelova1,2, L. Slavov2, B. Blagoev2, M. Iliev1   
1 Faculty of Biology, University of Sofia, Bulgaria, 1164 Sofia, 8 Dragan Tsankov Blvd.
2 Institute of Electronics, BAS, Bulgaria, 1784 Sofia, 72, Tzarigradsko chaussee Blvd.
Introduction
The neutrophilic iron bacteria from the group Sphaerotilus-Leptothrix are widely spread in different natural habitats. They are typical ß- Proteobacteria with different morphology and physiology but all of them are able to oxidise Fe2+ at neutral pH and to form insoluble ferric hydroxides. The interest to these bacteria increased in the recent years because the possibility for application of the biogenic hydroxides formed in different nanotechnologies [1] as well as pigments, catalysts, absorbents etc [2]. These bacteria forms sheaths which are also of interest but is very difficult to have been obtained probably because their slowly formations or unknown yet reason.
Aim
The goal of this study is to isolate from natural habitats pure cultures of this group bacteria, to establish the most suitable laboratory conditions for cultivating and formation of various biogenic oxides characterized by Raman spectroscopy and X-ray Diffraction (XDR).
Materials, Methods and Results
Sampling region a b c d
5 μm
Typical deposits of iron bacteria in
Vitosha Mountain (1783 m altitude)
Microscopic images of the samples from the area of ​​sampling: (a) and (b) SEM of bacterial cells, (с) SEM of sheaths – x, (d) light microscopy image of sheaths.
Molecular methods (PCR detection assay)
Fehrenbach Flasks
Cultivation
(а, b) SEM of bacteria of the genus Leptothrix cultured in medium: a) Panoramic view; с) Typical cell shape with a rough surface; (c) SEM of bacteria cultured in an Isolation medium
Amplification profile of mofA gene of Leptothrix spp.
Raman spectra of the biogenic material
Images by light microscopy in areas where was focused laser beam of the Raman spectroscopy
c.m. “Lieske”
c.m. “IM”
c.m. “Adler”
(а), (c) lepidocrocite (γ-FeO(OH));
(b) goethite (α-FeO(OH))
(а), (b) lepidocrocite (γ-FeO(OH));
(c) и (d) magnetite (Fe3O4)
(а), (b) goethite (α-FeO(OH))
XRD spectra of the biogenic material
c.m. “IM”
c.m. “Adler”
c.m. “Lieske”
Goethite – % nm
Lepidocrocite – % nm
Goethite – % nm
Lepidocrocite – % nm
- Magnetite – 8.14 % nm
Lepidocrocite – % nm
Magnetite – % nm
- Goethite – % nm
References:
[1] Katsoyiannis I. and Zouboulis A., Water Qual. Res. J. 41 (2006) 117–129.
[2] Sawayama M. et al., Curr. Microbiol. 63 (2011) 173 –180.
Conclusions
The most suitable conditions for culturing bacteria of the group Sphaerotilus-Leptothrix as well as the formation of biogenic iron oxides are the media IM, AM and LM. XRD data confirmed the results of Raman spectroscopy, as in addition gives the amount of the different nanosized oxides contained and their percentage ratio.
The experiments must be continued into the direction for optimization of the laboratory cultivation of the bacteria. This optimization must be in order to receive bigger amounts of monophase iron containing by-products, with suitable magnetic characteristics.
Acknowledgements
This work was supported by the Bulgarian National Science Fund under project ДИД 02/38/2009.