The quarternary molecular architecture of TetA, a secondary tetracycline transporter from Escherichia coli

TetA, a tetracycline cation/proton antiporter, was expressed in Escherichia coli with a C-terminal tag of six histidines, solubilized in dodecyl maltoside and purified in a single step using Ni2+ affinity chromatography. Two-dimensional crystals were obtained after reconstitution of purified protein with lipids. Electron microscopy of negatively stained crystals revealed a trigonal symmetry, from which we infer that this secondary transporter has a trimeric structure. An overall molecular envelope can be described by a triangle of side approximately 100 A enclosing a central stain-filled depression. These dimensions are consistent with those obtained from projection views of single, isolated TetA particles that also display a trimeric architecture, confirming that the threefold symmetry is not simply a consequence of crystal-packing interactions. These data represent the first direct view of the quarternary arrangement of any antibiotic efflux pump. They are fully consistent with biochemical data on TetA, which indicate that it functions as a multimer and that the monomer consists of two domains, one of which plays the major part in oligomerization interactions.     

Indole-3-acetic acid accumulation during poplar rhizogenesis revealed by immunohistochemistry

Poplar hybrid 741 [Populus alba × (P. davidiana + P. simonii) × P. tomentosa] leaves were rooted within 8 d when cultured in vitro on 1/2 Murashige and Skoog (MS) medium. The spatial distribution of endogenous indole-3-acetic acid (IAA) in the rhizogenesis was investigated, using an immunohistochemical approach. In addition, the effect of 2,3,5-triiodobenzoic acid (TIBA) on IAA distribution was also analyzed. The results showed that a strong IAA signal was detected in the vascular bundles of the basal regions of the petioles 3 d after root induction. Furthermore, the signal in vascular bundles of the basal regions of the petioles was stronger than that of the middle regions of the petioles. Application of TIBA on lamina delayed both the accumulation of IAA in the vascular bundles and rhizogenesis. These data indicate that an endogenous IAA rise in vascular bundles is among the first signals leading to the rhizogenesis, and that it results from transportation of the hormone from the lamina of the leaf to the base of the petiole, rather than by in situ IAA generation.     

无色素腺棉籽蛋白粉与棉子油的制备

低棉酚棉籽为高蛋白含油的植物资源,适宜于水溶法制备油及蛋白粉,出油率一般可达９５％。     

Grazing-induced legacy effects enhance plant adaption to drought by larger root allocation plasticity

放牧诱导的植物遗留效应可以通过较大的根系分配可塑性增强其干旱适应性 为探索植物的放牧遗留效应是否有利于天然草原生态系统应对干旱环境,我们采集了 内蒙古典型草原自由放牧和多年围封样地内的冰草(Agropyron cristatum)和黄囊苔草(Carex korshinskyi)幼苗 进行了温室控水试验。研究结果表明,干旱处理对自由放牧样地采集的冰草和黄囊苔草子株生物量、子株数量和总生物量的影响较小;自由放牧区的冰草与黄囊苔草较强的干旱适应性可部分由干旱处理下较大的根系分配可塑性来解释。本研究结果表明合理放牧是天然草原适应气候变化的潜在管理办法之一。     

Dynamics and diversity of a microbial community during the fermentation of industrialized <Emphasis Type="Italic">Qingcai</Emphasis> paocai,a traditional Chinese fermented vegetable food,as assessed by Illumina MiSeq sequencing,DGGE and qPCR assay

Paocai is a traditional Chinese fermented food and typically produced via spontaneous fermentation. We have investigated the microbial community utilized for the fermentation of industrialized Qingcai paocai using the combination of Illumina MiSeq sequencing, PCR-mediated denaturing gradient gel electrophoresis (PCR-DGGE) and quantitative PCR (qPCR) assay. Three main phyla, namely Firmicutes, Proteobacteria and Bacteroidetes, were identified by both MiSeq sequencing and PCR-DGGE. The dominant genera observed in the fermentation were Lactobacillus, Pseudomonas, Vibrio and Halomonas. Most genera affiliated with Proteobacteria or Bacteroidetes were detected more often during the earlier part of the fermentation, while Lactobacillus (affiliated with Firmicutes) was dominant during the later fermentation stages. Fungal community analysis revealed that Debaryomyces, Pichia and Kazachstania were the main fungal genera present in industrialized Qingcai paocai, with Debaryomyces being the most dominant during the fermentation process. The quantities of dominant genera Lactobacillus and Debaryomyces were monitored using qPCR and shown to be 10⁹–10¹² and 10⁶–10¹⁰ copies/mL, respectively. During the later fermentation process of industrialized Qingcai paocai, Lactobacillus and Debaryomyces were present at 10¹¹ and 10⁸ copies/mL, respectively. These results facilitate further understanding of the unique microbial ecosystem during the fermentation of industrialized Qingcai paocai and guide future improvement of the fermentation process.     

A novel peroxiredoxin from the antagonistic endophytic bacterium Enterobacter sp. V1 contributes to cotton resistance against Verticillium dahliae

Plant and Soil - [Aims] To reveal the molecular mechanism of endophytic bacteria in Verticillium wilt-resistant cottons and deeply understand the interaction between soil and plants. [Methods]...