A. A. Shapkin

Investigations of Iron Minerals Formed by Dissimilatory Alkaliphilic Bacterium with 57Fe Mössbauer Spectroscopy

Anaerobic alkaliphilic bacterium of Geoalkalibacter ferrihydriticus type (strain Z‐0531), isolated from a bottom sediment sample from the weakly mineralized soda Lake Khadyn, have been analyzed. The strain uses the amorphous Fe(III)‐hydroxide (AFH) as an electron acceptor and acetate CH3COO− as an electron donor. Mossbauer investigations of solid phase samples obtained during the process of the bacterium growth were carried out at room temperature, 77.8 K, 4.2 K without and with the presence of an external magnetic field (6 T) applied perpendicular to the γ‐bebam.

Mössbauer study of formation of iron oxides and carbonate by dissimilatory alkaliphilic bacterium

The process of amorphous Fe(III)-hydroxide (AFH) reduction by anaerobic alkaliphilic bacterium – Geoalkalibacter ferrihydriticus (strain Z-0531) was investigated by Mossbauer spectroscopy methods. Strain Z-0531 was isolated from the sediments of soda Lake Khadyn (Tuva, Russian Federation). The influence of AFH concentration and the concentration of anthraquinone-2,6-disulfonate added to the cultivation medium as well as the incubation time influence on the reducing process were studied. It was found that increase in the time of cultivation of bacteria led to an increase in the relative content of phases containing ferrous atoms that could be explained by the adaptation of bacterium to the cultivation medium.

Mössbauer and Magnetic Study of Solid Phases Formed by Dissimilatory Iron-Reducing Bacteria

Mössbauer investigations of solid phases that were formed during the reduction of amorphous synthesized ferrihydrite (SF) by thermophilic anaerobic iron-reducing bacterium Thermincola ferriacetica (strain Z-0001) and alkaliphilic anaerobic iron-reducing bacterium Geoalkalibacter ferrihydriticus (strain Z-0531) were carried out at room, liquid nitrogen and helium temperatures in the presence or the absence of an external magnetic field (6 T). The magnetization M (T, H) was measured in the temperature interval 80-300 K and magnetic field up to 10 kOe. It was performed zero field cooling (ZFC) and field cooling (FC) measurements of M (T).

Mössbauer study of bacterial iron-reduction processes in natural glauconite and biotite

Interaction between a bacterial monoculture of alkaliphylic G. ferrihydriticus along with binary cultures of G. ferrihydriticus and cellulolytic C. alkalicellulosi and natural biotite and glauconite under alkaliphylic conditions is investigated by means of Mössbauer spectroscopy. Measurements were performed over a range of temperatures from T = 4.8 K to T = 300 K. It was found that a new magnetically ordered phase was formed during culture growth. This new phase was a mixture of nonstoichiometric magnetite and maghemite. The relative amount of the magnetically ordered phase in the monoculture of G. ferrihydriticus when interacting with glauconite is less than in the case of the binary culture. Iron reduction glauconite is also more intense than in biotite.

Mössbauer study of biogenic formation processes of iron minerals

Mossbauer investigations of iron minerals formed during the process of synthesized ferrihydrite (SF) reduction by anaerobic alkaliphilic bacterium Geoalkalibacter ferrihydriticus and anaerobic thermophilic bacterium Thermincola ferriacetica were carried out involving magnetization measurements. The influence of T. ferriacetica and G. ferrihydriticus growth media on SF was investigated. It was found that SF after its interaction with the mineral media was almost identical. There were also analyzed minerals that formed during the growth of binary culture of Geoalkalibacter ferrihydriticus and Anaerobacillus alkalilacustris at the concentrations of SF equal to 10mM. The new phase formed under this concentration is probably of FeII-FeIII (oxy-)hydroxycarbonate nature. Mossbauer spectroscopy showed that in all experiments where magnetically ordered phases formed by dissimilatory iron-reducing bacteria, a mixture of nonstoichiometric magnetite (Fe3O4) and maghemite (γ-Fe2O3) was observed.

Investigation of Iron Mineral Formation by Dissimilatory Alcalophilic Bacterium Geoalkalibacter Ferrihydriticus Using Mössbauer Spectroscopy

Formation of iron-bearing minerals by the dissimilatory alcalophilic bacterium Geoalkalibacter ferrihydriticus (strain Z-0531) under controlled laboratory conditions was studied using Mössbauer spectroscopy. Strain Z-0531 was isolated from bottom sediments of Lake Khadyn (Tyva, Russia), a soda lake. The effect of the concentration of amorphous iron hydroxide (AFH) and anthraquinone-2,6-disulfonate (quinone) added to the medium was studied along with the effect of the incubation time on iron reduction.

Mössbauer Study of Microbial Synthesis of Iron-Containing Nanoparticles

Mössbauer studies of bioreduction products stabilized by acetone and ethanol were carried out at wide temperature range from 80 K to room temperature and in external magnetic field applied perpendicular to γ-beam at room temperature. The initial products (mixture of non-stoichiometric magnetite and maghemite) were formed during the iron reduction of synthesized ferrihydrite by bacterium G. ferrihydriticus. The addition of acetone and ethanol led to slight particle size decrease. The average size and magnetic moments were 11.2 nm and 524 µB, respectively.