新疆棉田土壤固氮菌遗传多样性分析

利用ERIC-PCR和16SrDNA全序列测定方法,研究了新疆棉田土壤中分离获得的58株固氮菌的遗传多样性及系统发育。采用平均连锁法(UPGMA)分析ERIC-PCR的聚类结果表明在Watson距离为0.65左右时可以将供试菌株分为9个大群。选取ERIC-PCR各群中代表菌株进行16SrRNA全序列测定分析,结果表明这些菌株分别属于Enterobacter、Bacillus、Acinetobacter、Pseudomonas、Serratia和Yersinia6个属。     

Synthesis, characterization, and in vitro evaluation of long-chain hyperbranched poly(ethylene glycol) as drug carrier

A series of novel long-chain hyperbranched poly(ethylene glycol)s (LHPEGs) with biodegradable connections were designed and synthesized in one pot through proton-transfer polymerization using PEG and commercial glycidyl methacrylate as monomers and potassium hydride as catalyst. The LHPEGs were hydrolyzed at neutral pH resulting in the decrease of molecular weights. In vitro evaluation demonstrated that LHPEGs were biocompatible and displayed negligible hemolytic activity. The efficient cellular uptake of LHPEGs was confirmed by flow cytometry and confocal laser scanning microscopy. Moreover, conjugation of a model hydrophobic anticancer drug methotrexate to LHPEGs inhibited the proliferation of a human cervical carcinoma Hela cell line. MTT assay indicated that the conjugated methotrexate dose required for 50% cellular growth inhibition against Hela cells was 20 μg/mL. By combining the advantages of long-chain hyperbranched structure and PEG, LHPEG provides a promising drug carrier for therapeutic fields.     

Genetic Diversity and Geographical Differentiation of <Emphasis Type="Italic">Desmodium triflorum</Emphasis> (L.) DC. in South China Revealed by AFLP Markers

High levels of genetic variation enable species to adapt to changing environments and provide plant breeders with the raw materials necessary for artificial selection. In the present study, six AFLP primer pairs were used to assess the genetic diversity of Desmodium triflorum (L.) DC. from 12 populations in South China. A high percentage of polymorphic loci (P = 76.16%) and high total gene diversity (H _T = 0.310) were found, indicating that the genetic diversity of D. triflorum is high at the species level. Genetic diversity was also relatively high at the population level (P = 55.85%, H _e = 0.230). The coefficient of gene differentiation among populations (G _ST) was 0.255, indicating that while most genetic diversity resided within populations, there was also considerable differentiation among populations. AMOVA also indicated 24.29% of the total variation to be partitioned among populations (Φ_ST = 0.243). UPGMA clustering analysis based on genetic distances showed that the 12 populations could be separated into three subgroups: an eastern, a western, and a central-southern subgroup. However, a Mantel test revealed no significant correlation (r = 0.286, p = 0.983) between the geographical distances and genetic distances separating these populations; mountain barriers to gene flow and human disturbance may have confounded these correlations. The present study has provided some fundamental genetic data that will be of use in the exploitation of D. triflorum.     

Effect of solid bed-materials on vegetative cells of <Emphasis Type="Italic">Nostoc flagelliforme</Emphasis>

Nostoc flagelliforme was cultivated on three solid bed-materials which have different wettability. The results show that the wettability of solid bed-materials is very important to the need for water in N. flagelliforme, and also greatly affects photosynthetic activity, polysaccharide secretion and the morphology of the cells. Glass residue has the best wettability, followed by sand, and then nylon6 (PA6). We show that only sand is suitable for the growth of N. flagelliforme. When cultivated on sand for 100 days, the cells maintained a typical rosary-like shape. On glass residue, two to three vegetative cells formed a group with slime. On PA6, cells were in the form of loose group with slimes. N. flagelliforme is applicable to desert control as it cannot only grow on the sand, but also adhere to sand to form a biological crust.     

Phylogeographic patterns and conservation units of a vulnerable species,Cabot’s tragopan (<Emphasis Type="Italic">Tragopan caboti</Emphasis>), endemic to southeast China

Cabot’s tragopan (Tragopan caboti) is a pheasant endemic to southeast China and is protected under both national and global legislation due to ongoing decline in population size and increased habitat fragmentation. We investigated the phylogeographic patterns and examined the consistency between evolutionary units and assumed subspecies taxonomy in this species. Six populations across the whole species presenting a wide distribution range were sampled and two mitochondrial DNA segments (control region, CR and cytochrome b, cyt b) were used in this study. The results demonstrated a high level of genetic diversity (h = 0.97 in CR and 0.78 in cyt b) and significant differentiation among populations. Phylogenetic analyses strongly indicated two reciprocally monophyletic clades named the “West group” and “East group” that were not consistent with the present subspecies regional distribution. The divergence time between the two groups was estimated to be around 5.54 × 10⁵–8.7 × 10⁵ years ago, and the expansion times of the two groups were close (about 3 × 10⁵ years ago), indicating the effect of glaciation in intraspecific differentiation. Based on the results of genetic analyses combined with geographic isolation and distinct population history, our findings suggest that two management units (MUs) should be defined in T. caboti for conservation.     

Affinity and Specificity of Ciprofloxacin-Bovine Serum Albumin Interactions: Spectroscopic Approach

Fluorescence spectroscopy in combination with UV–Vis absorption spectroscopy were employed to investigate the binding of an antibacterial drug Ciprofloxacin (CPFX) to bovine serum albumin (BSA) under the physiological conditions. In the discussion of the quenching mechanism, it was proved that the fluorescence quenching of BSA by CPFX is a result of the formation of CPFX-BSA complex. Binding parameters were determined using the modified Stern-Volmer equation and Scatchard equation to provide a measure of the binding affinity between CPFX and BSA. The results of thermodynamic parameters ΔG, ΔH, ΔS, at different temperatures indicate that the electrostatic interactions play a major role for CPFX-BSA association. Site marker competitive experiments indicated that the binding of CPFX to BSA primarily took place in site I. Furthermore, the effect of metal ions to CPFX-BSA system was studied, and the distance r between donor (BSA) and acceptor (CPFX) was obtained according to fluorescence resonance energy transfer (FRET). The conformation of BSA upon CPFX binding was evaluated by measuring synchronous fluorescence properties of the CPFX-BSA complex.