红谷霉素对金黄色葡萄球菌抑菌机制的研究

红谷霉素是一种抗细菌的新型抗生素。为探讨红谷霉素对金黄色葡萄球菌的抑菌机制,本文采用浓度为EC50和EC90的红谷霉素对试验菌株进行处理,并设空白对照,测定供试菌株的胞外多糖、细胞膜渗透性和生物大分子(DNA、RNA、蛋白质和胞外酶活性)。结果显示:红谷霉素对金黄色葡萄球菌的抑制作用首先表现在对核酸合成的抑制,由于核酸的合成受阻,引起菌体内的蛋白质和其它的生物大分子的合成受阻,细菌细胞膜通透性改变。透视电镜照片显示:红谷霉素处理后金黄色葡萄球菌菌体内部的原生质体明显变稀。     

Cadmium Uptake,Translocation, and Tolerance in <Emphasis Type="Italic">AHA1OX Arabidopsis thaliana</Emphasis>

Information on cadmium (Cd) uptake and transport is essential to understand better the physiology of Cd tolerance in plants. In this study, Cd uptake, translocation, and tolerance were investigated in AHA1 (Arabidopsis plasma membrane H⁺-ATPase gene) overexpressed plants. Exposed to 10 μM CdCl₂, AHA1OX showed a higher root elongation, accumulated more Cd, and maintained better integrity of nucleus membrane of root tips in comparison to the control plant (WT), suggesting that AHA1OX was more Cd tolerant than WT. To investigate Cd tolerance mechanism of AHA1OX plants, we measured the activity of plasma membrane H⁺-ATPase and the secretion of citrate. Results indicated that treatment with 10 μM of Cd stimulated the activity of plasma membrane H⁺-ATPase and the secretion of citrate, while 30 μM of Cd inhibited them. AHA1OX had higher activity of H⁺-ATPase and secretion of citrate than WT. Addition of citrate enhanced root-to-shoot translocation of Cd significantly. A higher root-to-shoot Cd translocation was observed in AHA1OX than in WT plants. Treatment with low temperature or metabolic inhibitor (carbonyl cyanide m-chlorophenylhydrazone) inhibited Cd uptake and translocation. The study of Cd forms using sequential extraction indicated that Cd was mainly present as a protein-bound form, and AHA1OX had more water-soluble Cd than WT. Taken together, our results suggested that the Cd tolerance of AHA1OX was associated with its root-to-shoot Cd translocation and secretion of citrate, which converts Cd²⁺ into less toxic and more easily transportable forms in plant cells.     

天山冻土产低温脂肪酶菌株的筛选及其多样性分析

【目的】通过天山冻土细菌的分离和产低温脂肪酶菌株的筛选,了解天山冻土微生物的物种多样性和产脂肪酶菌株的系统发育多样性,为高效低温脂肪酶生物技术奠定基础。【方法】采用稀浓度的R2A、TSB平板涂布分离天山冻土中可培养细菌,通过选择性培养基筛选产低温脂肪酶的菌株。采用细菌常规生理生化实验、最适生长温度、耐盐性、产酶性能对分离菌株的生理学进行研究,通过16S rRNA基因序列分析确定产脂肪酶菌种的系统进化地位,通过BOX-PCR指纹技术对16S rRNA基因高度同源性的菌株进一步区分。【结果】分离筛选到78株可培养低温菌,选择培养基显示有17株可产低温脂肪酶,其中8株在两种选择培养基中均可产脂肪酶和酯酶。17株产酶菌分别隶属于5个系统发育类群、6个属,其中假单胞菌属(Pseudomonas)占大多数(58.9%)。【结论】天山冻土中产低温脂肪酶的细菌具有较丰富的系统发育多样性,依据生长温度,均属于耐冷菌。     

Profile and Determinants of Retinal Optical Intensity in Normal Eyes with Spectral Domain Optical Coherence Tomography

Purpose

To investigate the profile and determinants of retinal optical intensity in normal subjects using 3D spectral domain optical coherence tomography (SD OCT).

Methods

A total of 231 eyes from 231 healthy subjects ranging in age from 18 to 80 years were included and underwent a 3D OCT scan. Forty-four eyes were randomly chosen to be scanned by two operators for reproducibility analysis. Distribution of optical intensity of each layer and regions specified by the Early Treatment of Diabetic Retinopathy Study (ETDRS) were investigated by analyzing the OCT raw data with our automatic graph-based algorithm. Univariate and multivariate analyses were performed between retinal optical intensity and sex, age, height, weight, spherical equivalent (SE), axial length, image quality, disc area and rim/disc area ratio (R/D area ratio).

Results

For optical intensity measurements, the intraclass correlation coefficient of each layer ranged from 0.815 to 0.941, indicating good reproducibility. Optical intensity was lowest in the central area of retinal nerve fiber layer, ganglion cell layer, inner plexiform layer, inner nuclear layer, outer plexiform layer and photoreceptor layer, except for the retinal pigment epithelium (RPE). Optical intensity was positively correlated with image quality in all retinal layers (0.553<β<0.851, p<0.01), and negatively correlated with age in most retinal layers (-0.362<β<-0.179, p<0.01), except for the RPE (β = 0.456, p<0.01), outer nuclear layer and photoreceptor layer (p>0.05). There was no relationship between retinal optical intensity and sex, height, weight, SE, axial length, disc area and R/D area ratio.

Conclusions

There was a specific pattern of distribution of retinal optical intensity in different regions. The optical intensity was affected by image quality and age. Image quality can be used as a reference for normalization. The effect of age needs to be taken into consideration when using OCT for diagnosis.     

Molecular Evidence for the Hybrid Origin of Ilex dabieshanensis (Aquifoliaceae)

Ilex, the largest genus of dioecious woody plants, is a good study system to assess the role of hybridization in speciation and evolution. Ilex dabieshanensis, a tree endemic to Dabieshan Mountains region, was initially described as a new species. Based on morphological intermediacy and sympatric distribution with its putative parental species, I. cornuta and I. latifolia, we proposed it as a natural hybrid between them. In this study, we sequenced one chloroplast intergenic spacer (trnH-psbA) and two nuclear genes (gapC and nepGS) in I. dabieshanensis and its putative parental species to test the hybrid origin hypothesis. Our results showed that there were one to two differentially fixed sequence differences between I. cornuta and I. latifolia at the two nuclear genes. Twelve of the 14 individuals of I. dabieshanensis exhibited additivity in chromatograms on these differentially fixed sites at both nuclear genes, and the remaining two exhibited additivity in chromatograms on the fixed site at only the nepGS gene. Except one haplotype of I. cornuta at the nepGS gene, all of the haplotypes of I. cornuta at the two nuclear genes were well separated from those of I. latifolia, and most haplotypes of I. dabieshanensis were shared with those of I. cornuta and I. latifolia. Phylogenetic analysis of these haplotypes was largely consistent with haplotype network analysis. I. cornuta and I. latifolia differed by two nucleotide substitutions in the chloroplast intergenic spacer, and 12 individuals of I. dabieshanensis had the same sequences as I. latifolia, while the remaining two were identical with I. cornuta. The molecular data provide convincing evidence for the hybrid origin of I. dabieshanensis and asymmetrical direction of hybridization. One haplotype of I. cornuta at the nepGS gene was nested with those of I. latifolia, indicating introgression to I. cornuta.     

Inverse analysis of coupled carbon-nitrogen cycles against multiple datasets at ambient and elevated CO2

Aims Carbon (C) sequestration in terrestrial ecosystems is strongly regulated by nitrogen (N) processes. However, key parameters that determine the degree of N regulation on terrestrial C sequestration have not been well quantified.Methods Here, we used a Bayesian probabilistic inversion approach to estimate 14 target parameters related to ecosystem C and N interactions from 19 datasets obtained from Duke Forests under ambient and elevated carbon dioxide (CO₂).Important findings Our results indicated that 8 of the 14 target parameters, such as C:N ratios in most ecosystem compartments, plant N uptake and external N input, were well constrained by available datasets whereas the others, such as N allocation coefficients, N loss and the initial value of mineral N pool were poorly constrained. Our analysis showed that elevated CO₂ led to the increases in C:N ratios in foliage, fine roots and litter. Moreover, elevated CO₂ stimulated plant N uptake and increased ecosystem N capital in Duke Forests by 25.2 and 8.5%, respectively. In addition, elevated CO₂ resulted in the decrease of C exit rates (i.e. increases in C residence times) in foliage, woody biomass, structural litter and passive soil organic matter, but the increase of C exit rate in fine roots. Our results demonstrated that CO₂ enrichment substantially altered key parameters in determining terrestrial C and N interactions, which have profound implications for model improvement and predictions of future C sequestration in terrestrial ecosystems in response to global change.     

Construction of High-Density Linkage Maps of Populus deltoides × P. simonii Using Restriction-Site Associated DNA Sequencing

Although numerous linkage maps have been constructed in the genus Populus, they are typically sparse and thus have limited applications due to low throughput of traditional molecular markers. Restriction-site associated DNA sequencing (RADSeq) technology allows us to identify a large number of single nucleotide polymorphisms (SNP) across genomes of many individuals in a fast and cost-effective way, and makes it possible to construct high-density genetic linkage maps. We performed RADSeq for 299 progeny and their two parents in an F₁ hybrid population generated by crossing the female Populus deltoides ‘I-69’ and male Populus simonii ‘L3’. A total of 2,545 high quality SNP markers were obtained and two parent-specific linkage maps were constructed. The female genetic map contained 1601 SNPs and 20 linkage groups, spanning 4,249.12 cM of the genome with an average distance of 2.69 cM between adjacent markers, while the male map consisted of 940 SNPs and also 20 linkage groups with a total length of 3,816.24 cM and an average marker interval distance of 4.15 cM. Finally, our analysis revealed that synteny and collinearity are highly conserved between the parental linkage maps and the reference genome of P. trichocarpa. We demonstrated that RAD sequencing is a powerful technique capable of rapidly generating a large number of SNPs for constructing genetic maps in outbred forest trees. The high-quality linkage maps constructed here provided reliable genetic resources to facilitate locating quantitative trait loci (QTLs) that control growth and wood quality traits in the hybrid population.     

Signaling Cascades Governing Cdc42-Mediated Chondrogenic Differentiation and Mensenchymal Condensation

Endochondral ossification consists of successive steps of chondrocyte differentiation, including mesenchymal condensation, differentiation of chondrocytes, and hypertrophy followed by mineralization and ossification. Loss-of-function studies have revealed that abnormal growth plate cartilage of the Cdc42 mutant contributes to the defects in endochondral bone formation. Here, we have investigated the roles of Cdc42 in osteogenesis and signaling cascades governing Cdc42-mediated chondrogenic differentiation. Though deletion of Cdc42 in limb mesenchymal progenitors led to severe defects in endochondral ossification, either ablation of Cdc42 in limb preosteoblasts or knockdown of Cdc42 in vitro had no obvious effects on bone formation and osteoblast differentiation. However, in Cdc42 mutant limb buds, loss of Cdc42 in mesenchymal progenitors led to marked inactivation of p38 and Smad1/5, and in micromass cultures, Cdc42 lay on the upstream of p38 to activate Smad1/5 in bone morphogenetic protein-2-induced mesenchymal condensation. Finally, Cdc42 also lay on the upstream of protein kinase B to transactivate Sox9 and subsequently induced the expression of chondrocyte differential marker in transforming growth factor-β1-induced chondrogenesis. Taken together, by using biochemical and genetic approaches, we have demonstrated that Cdc42 is involved not in osteogenesis but in chondrogenesis in which the BMP2/Cdc42/Pak/p38/Smad signaling module promotes mesenchymal condensation and the TGF-β/Cdc42/Pak/Akt/Sox9 signaling module facilitates chondrogenic differentiation.     

The Role of Porcine Monocyte Derived Dendritic Cells (MoDC) in the Inflammation Storm Caused by Streptococcus suis Serotype 2 Infection

Background

Streptococcus suis is an important swine pathogen and zoonotic agent. Infection with this highly pathogenic strain can cause streptococcal toxic shock-like syndrome (STSLS), characterized by a Th-1 inflammatory cytokine storm, and a high mortality rate. Monocyte derived dendritic cells (MoDCs) are known to stimulate Th-1 cell differentiation, but the role of MoDCs in STSLS remains to be elucidated.

Methodology and Findings

Porcine CD14-positive monocytes, purified from peripheral blood mononuclear cells (PBMCs), were used to generate MoDCs using granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4). Highly pure MoDCs were generated, as proved by their morphology, phenotype analysis, phagocytic ability, and induction of T cells proliferation. The MoDCs were further stimulated by the virulent S. suis serotype 2 (SS2) SC19 strain which triggered a strong release of several pro-inflammatory cytokines, including IL-1β, IL-8, TNF-α, IFN-γ, and IL-12. Furthermore, the stimulated MoDCs induced CD4⁺ T cell differentiation towards Th-1 cells in vitro.

Conclusions

The results of this study indicated that the porcine MoDCs stimulated by SS2 could release high levels of Th-1 inflammatory cytokines and induce CD4⁺ T cell differentiation towards Th-1 cells. Hence, it is likely that porcine MoDCs play an important role in the STSLS caused by SS2.