Samples of natural and synthetic tochilinites and valleriites were investigated by Mössbauer spectroscopy. Synthesis of tochilinite was carried out at different temperatures and Fe/Mg ratio in the initial mixture. The relative amounts of obtained phases as functions of Mg atom relative content in the initial mixture were derived. It was shown that Mg atoms preferred to occupy one of two nonequivalent positions in brucite-like layers when entering the tochilinite structure. Parameters of hyperfine interaction were determined for valleriite and crystal chemical identification of 57 Fe subspectra was carried out.PACS : 76.80.+y
The genus Carboxydocella forms a deeply branching family in the class Clostridia and is currently represented by three physiologically diverse species of thermophilic prokaryotes. The type strain of the type species, Carboxydocella thermautotrophica 41T, is an obligate chemolithoautotroph growing exclusively by hydrogenogenic CO oxidation. Another strain, isolated from a hot spring at Uzon caldera, Kamchatka in the course of this work, is capable of coupling carboxydotrophy and dissimilatory reduction of Fe(III) from oxic and phyllosilicate minerals. The processes of carboxydotrophy and Fe(III) reduction appeared to be interdependent in this strain. The genomes of both isolates were sequenced, assembled into single chromosome sequences (for strain 41T a plasmid sequence was also assembled) and analyzed. Genome analysis revealed that each of the two strains possessed six genes encoding diverse Ni,Fe-containing CO dehydrogenases (maximum reported in complete prokaryotic genomes), indicating crucial role of carbon monoxide in C. thermautotrophica metabolism. Both strains possessed a set of 30 multiheme c-type cytochromes, but only the newly isolated Fe-reducing strain 019 had one extra gene of a 17-heme cytochrome, which is proposed to represent a novel determinant of dissimilatory iron reduction in prokaryotes. Mössbauer studies revealed that strain 019 induced reductive transformation of the abundant ferric/ferrous-mica mineral glauconite to siderite during carboxydotrophic growth. Reconstruction of the C. thermautotrophica strains energy metabolism is the first comprehensive genome analysis of a representative of the deep phylogenetic branch Clostridia Incertae Sedis, family V. Our data provide insights into energy metabolism of C. thermautotrophica with an emphasis on its ecological implications.
Samples obtained as a result of the valleriite synthesis process under different conditions (temperature and proportion Cu:Fe:Mg in the initial mixture) were investigated by 57 Fe Mössbauer spectroscopy with attraction data of X-ray diffraction. Parameters of hyperfine interactions for valleriite were determined and crystal chemical identification of 57 Fe subspectra was carried out. It was found that valleriite was formed in samples synthesized at 150 • C and 180 • C and not formed in samples synthesized at 250 • C.
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