Mutualism between bacteria and eukaryotes has essential roles in the history of life, but the evolution of their compatibility is poorly understood. Here we show that different Sinorhizobium strains can form either nitrogen-fixing nodules or uninfected pseudonodules on certain cultivated soybeans, while being all effective microsymbionts of some wild soybeans. However, a few well-infected nodules can be found on a commercial soybean using inocula containing a mixed pool of Tn5 insertion mutants derived from an incompatible strain. Reverse genetics and genome sequencing of compatible mutants demonstrated that inactivation of T3SS (type three secretion system) accounted for this phenotypic change. These mutations in the T3SS gene cluster were dominated by parallel transpositions of insertion sequences (ISs) other than the introduced Tn5. This genetic and phenotypic change can also be achieved in an experimental evolution scenario on a laboratory time scale using incompatible wild-type strains as inocula. The ISs acting in the adaptive evolution of Sinorhizobium strains exhibit broader phyletic and replicon distributions than other ISs, and prefer target sequences of low GC% content, a characteristic feature of symbiosis plasmid where T3SS genes are located. These findings suggest an important role of co-evolved ISs in the adaptive evolution of rhizobial compatibility.

High-pressure Raman studies have been carried out on single crystalline C(60)(Fc)(2) nanosheets up to 25.4 GPa. Our results show that the charge transfer between Fc (ferrocene) and C(60) increases in the low-pressure range. Above 5 GPa, C(60) molecules start to form a chainlike polymer structure, and this polymerization is reversible upon decompression, in contrast to that of pristine C(60). The special layered structure of C(60)(Fc)(2) restricts the polymerization of C(60) molecules in some directions and explains the formation of the linear chainlike polymeric structure of the C(60) lattice under pressure. We suggest that the reversible polymerization is related to the increased charge transfer and the overridden steric repulsion of counterions.

Single crystalline C 70 nanotubes having a face-centered-cubic (fcc) structure with diameters in the nanometer scale were synthesized by a facile solution method. In-situ high pressure Raman spectroscopy and X-ray diffraction have been employed to study the structural stability and phase transitions of the pristine sample. We show that the molecular orientation related phase transition from the fcc structure to a rhombohedral structure occurs at about 1.5 GPa, which is ~1 GPa higher than in bulk C 70 . Also, the C 70 molecules themselves are more stable in the nanotubes than in bulk crystals, manifested by a partial amorphization at ~20 GPa. The crystal structure of C 70 nanotubes could partially return to the initial structure after a pressure cycle above 30.8 GPa, and the C 70 molecules were intact up to 43 GPa. The bulk modulus of C 70 nanotubes is measured to be ~50 GPa, which is twice larger than that of bulk C 70.2

No abstract

We report a synthesis of hydrogenated carbon nanospheres (HCNSs) via a facile solvothermal route at low temperatures (60-100 °C), using CHCl3 as the carbon source and potassium (K) as the reductant. Selective cleavage of the relatively lower stable C-Cl bonds (compared to C-H bonds) of the carbon precursor (CHCl3) by K metal results in the growth of HCNSs. The diameter of HCNSs ranges from 40 to 90 nm. The HCNSs have a graphite-like ordered carbon structure in spite of their high degree of hydrogenation. The HCNSs exhibit an average Brunauer-Emmett-Teller (BET) surface area of 43 m(2) g(-1), containing a small amount of mesopores and macropores in the structure. The nanospheres' sample as an anode material for lithium ion batteries (LIBs) has been studied. It exhibits a high discharge capacity (3539 mA h g(-1) in the first cycle, 978 mA h g(-1) after 50 cycles) and good cycling stability, demonstrating advantages as a promising candidate for anode materials in LIBs. The high capacity of the HCNSs is due to their unique nanostructures and high percentage hydrogenation, as well as hydrogenation induced structural defects.