Diallyl disulfide from garlic oil inhibits Pseudomonas aeruginosa virulence factors by inactivating key quorum sensing genes

Applied Microbiology and Biotechnology - Garlic oil can disrupt the quorum sensing (QS) pathways of the opportunistic pathogen Pseudomonas aeruginosa; however, the underlying mechanisms for this...     

GsCML27, a Gene Encoding a Calcium-Binding Ef-Hand Protein from Glycine soja,Plays Differential Roles in Plant Responses to Bicarbonate,Salt and Osmotic Stresses

Calcium, as the most widely accepted messenger, plays an important role in plant stress responses through calcium-dependent signaling pathways. The calmodulin-like family genes (CMLs) encode Ca²⁺ sensors and function in signaling transduction in response to environmental stimuli. However, until now, the function of plant CML proteins, especially soybean CMLs, is largely unknown. Here, we isolated a Glycine soja CML protein GsCML27, with four conserved EF-hands domains, and identified it as a calcium-binding protein through far-UV CD spectroscopy. We further found that expression of GsCML27 was induced by bicarbonate, salt and osmotic stresses. Interestingly, ectopic expression of GsCML27 in Arabidopsis enhanced plant tolerance to bicarbonate stress, but decreased the salt and osmotic tolerance during the seed germination and early growth stages. Furthermore, we found that ectopic expression of GsCML27 decreases salt tolerance through modifying both the cellular ionic (Na⁺, K⁺) content and the osmotic stress regulation. GsCML27 ectopic expression also decreased the expression levels of osmotic stress-responsive genes. Moreover, we also showed that GsCML27 localized in the whole cell, including cytoplasm, plasma membrane and nucleus in Arabidopsis protoplasts and onion epidermal cells, and displayed high expression in roots and embryos. Together, these data present evidence that GsCML27 as a Ca²⁺-binding EF-hand protein plays a role in plant responses to bicarbonate, salt and osmotic stresses.     

Molecular dynamics simulation of isothermal crystallisation of polymer chains around single polymer lamella

The isothermal crystallisation of polyethylene (PE) chains around single PE lamella in vacuum is investigated by molecular dynamic simulation. The crystallisation process is analysed in terms of the orientational order parameters, principal moments of inertia for the simulated systems. The effects of charge interactions between the polymer chains and lamella are discussed. It is found that the crystallisation process for uncharged systems can be divided into three stages: (1) adsorption, (2) orientation and (3) arrangement. The single polymer lamella changes a little during the three stages. PE chains are arranged parallel to the chain direction of the stems in the crystalline state. When considering the effect of charge interactions between the polymer chains and lamella, a different crystallisation process appears. The single polymer lamella is affected by the charged polymer chains.     

模拟穿透雨减少对锐齿栎(Quercus aliena var. acuteserrata)树干液流密度的影响

降水格局变化是全球气候变化的重要特征之一,未来气候变化下,较为频繁和严峻的干旱将威胁地球中纬度部分地区的森林,但森林植被如何响应季节性干旱胁迫及其机制尚不清楚。北亚热带-暖温带过渡区分布着以锐齿栎(Quercus aliena var.acuteserrata)为优势树种的落叶阔叶林,研究其水分蒸腾代谢过程对干旱的响应是评估气候变化对过渡区天然落叶阔叶林生态系统水碳影响的关键科学问题。在典型的锐齿栎天然林中通过开展模拟穿透雨减少大型野外实验,采用Granier热扩散式探针技术监测锐齿栎树干液流密度的动态变化,研究了不同径级锐齿栎树干液流密度对模拟干旱的响应规律。结果表明:(1)穿透雨减少对树干液流密度的影响呈现季节变异。在7月份,林内穿透雨减少显著降低了锐齿栎的树干液流密度,但生长季后期的10月份林内穿透雨减少反而使锐齿栎树干液流密度显著升高。(2)不同径级的锐齿栎树干液流密度在生长季内对干旱有不同的响应,特别是小径级的树干液流密度与其他径级有较多的不同。小径级的锐齿栎树干液流密度在5、7月份表现为减雨样地显著小于对照样地,在9、10月份则表现为减雨样地显著大于对照样地。中径级的锐齿栎树干液流密度在5、10月份表现为减雨样地显著大于对照样地,在7月份则表现为减雨样地极显著小于对照样地。大径级的锐齿栎树干液流密度在6、7月份表现为减雨样地显著小于对照样地,在10月份则表现为减雨样地显著大于对照样地。     

Novel Inhibitors of Staphylococcus aureus Virulence Gene Expression and Biofilm Formation

Staphylococcus aureus is a major human pathogen and one of the more prominent pathogens causing biofilm related infections in clinic. Antibiotic resistance in S. aureus such as methicillin resistance is approaching an epidemic level. Antibiotic resistance is widespread among major human pathogens and poses a serious problem for public health. Conventional antibiotics are either bacteriostatic or bacteriocidal, leading to strong selection for antibiotic resistant pathogens. An alternative approach of inhibiting pathogen virulence without inhibiting bacterial growth may minimize the selection pressure for resistance. In previous studies, we identified a chemical series of low molecular weight compounds capable of inhibiting group A streptococcus virulence following this alternative anti-microbial approach. In the current study, we demonstrated that two analogs of this class of novel anti-virulence compounds also inhibited virulence gene expression of S. aureus and exhibited an inhibitory effect on S. aureus biofilm formation. This class of anti-virulence compounds could be a starting point for development of novel anti-microbial agents against S. aureus.     

Surface Plasmon Resonance Imaging-Based Protein Array Chip System for Monitoring a Hexahistidine-Tagged Protein during Expression and Purification

A surface plasmon resonance imaging-based Ni²⁺-iminodiacetic acid-coated gold chip system was developed to enable specific detection of a hexahistidine-tagged recombinant protein in crude extracts or in column chromatography fractions. This system is especially advantageous for high-throughput analysis of multiple proteins.