Phylogeny of green sulfur bacteria on the basis of gene sequences of 16S rRNA and of the Fenna-Matthews-Olson protein

The phylogeny of green sulfur bacteria was studied on the basis of gene sequences of the 16S rRNA and of the Fenna-Matthews-Olson (FMO) protein. Representative and type strains (31 strains total) of most of the known species were analyzed. On the basis of fmoA gene sequences from Chlorobium tepidum ATCC 49652T and Chlorobium limicola DSM 249T available from the EMBL database, primers were constructed that allowed sequence analysis of a major part of the fmoA gene. The largely congruent phylogenetic relationship of sequences of the fmoA gene and of 16S rDNA gives considerable support to the phylogeny of green sulfur bacteria previously suggested on the basis of 16S rDNA sequences. Distinct groups of strains were recognized on the basis of 16S rDNA and FMO sequences and supported by characteristic signature amino acids of FMO. Marine strains formed clusters separate from freshwater strains. The resulting phylogenetic grouping and relationship of the green sulfur bacteria do not correlate with their current taxonomic classificatio

Flux-induced structural modification and phase transformations in a Pd40Ni40Si4P16 bulk-glassy alloy

International audienceIn order to uncover the mechanism of fluxing-enhanced undercooling, a study of the liquid structure in a Pd40Ni40Si4P16 bulk-glassy alloy was performed, which revealed that a flux-treated sample presents a shortened mean interatomic distance and an Increased coordination number within the first shell, which results in a more densely packed local structure than in an unfluxed sample. In addition to the usual influence of fluxing to effect a deactivation of nucleation catalysts to yield enhanced undercooling, structural studies have discovered a new effect of fluxing The local structural change induced by fluxing is associated with an increase in the delay time for the onset of nucleation. The prolonged transient period is also reflected by sluggish atomic transport in the fluxed sample, which promotes kinetic stability of the undercoole

Flux-induced structural modification and phase transformations in Pd40Ni40Si4P16 bulk-glassy alloy

International audienc