The Pseudomonas aeruginosa homeostasis enzyme AlgL clears the periplasmic space of accumulated alginate during polymer biosynthesis

Pseudomonas aeruginosa is an opportunistic human pathogen and a leading cause of chronic infection in the lungs of individuals with cystic fibrosis. After colonization, P. aeruginosa often undergoes a phenotypic conversion to mucoidy, characterized by overproduction of the alginate exopolysaccharide. This conversion is correlated with poorer patient prognoses. The majority of genes required for alginate synthesis, including the alginate lyase, algL, are located in a single operon. Previous investigations of AlgL have resulted in several divergent hypotheses regarding the protein’s role in alginate production. To address these discrepancies, we determined the structure of AlgL and, using multiple sequence alignments, identified key active site residues involved in alginate binding and catalysis. In vitro enzymatic analysis of active site mutants highlights R249 and Y256 as key residues required for alginate lyase activity. In a genetically engineered P. aeruginosa strain where alginate biosynthesis is under arabinose control, we found that AlgL is required for cell viability and maintaining membrane integrity during alginate production. We demonstrate that AlgL functions as a homeostasis enzyme to clear the periplasmic space of accumulated polymer. Constitutive expression of the AlgU/T sigma factor mitigates the effects of an algL deletion during alginate production, suggesting that an AlgU/T-regulated protein or proteins can compensate for an algL deletion. Together, our study demonstrates the role of AlgL in alginate biosynthesis, explains the discrepancies observed previously across other P. aeruginosa ΔalgL genetic backgrounds, and clarifies the existing divergent data regarding the function of AlgL as an alginate degrading enzyme.     

山药多糖对大鼠糖尿病肾病的治疗作用

目的：探讨山药多糖治疗大鼠糖尿病肾病的作用。方法：将sD大鼠40只随机分为4组（n=10）：对照组、模型组、苯那普利组和山药多糖组。复制糖尿病肾病大鼠模型,实验第10周统一处死大鼠,测定大鼠肾重／体重、血糖（Bs）、血脂及肾功能。结果：山药多糖能显著降低肾重／体重、血糖（BS）和血脂,改善肾功能。结论：山药多糖具有治疗糖尿病肾病的作用。     

Effect of water-soluble and insoluble non-starch polysaccharides isolated from wheat flour on the rheological properties of wheat starch gel

Water-soluble (WSP) and insoluble non-starch polysaccharides (WIP) were isolated from wheat flour to evaluate the effects of WSP and WIP on starch gel properties. Isolated WSP and WIP were added to two types of isolated wheat starch with different amylose content at a concentration of 3% based on the dry weight of starch. 30% starch gels were prepared and stored at 5 °C for 1, 8, or 24 h. The dynamic viscoelasticity of 30% starch gels mixed with WSP and WIP was measured using parallel plate geometry, showing that WSP and WIP affected the elastic component of starch gels in opposite ways. Adding WIP increased the storage shear modulus (G′) of starch gels, while adding WSP decreased G′ and dramatically increased the loss tangent (tan δ=G″/G′).     

天门冬多糖对人工感染鸡传染性支气管炎的治疗试验

旨在评价复方天门冬多糖注射液对鸡传染性支气管炎的临床治疗效果,为鸡传染性支气管炎临床治疗提供依据。以复方天门冬多糖注射液临床给药剂量筛选试验为基础,分别设置高剂量组、中剂量组、低剂量组、药物对照组、阳性对照组及空白对照组,运用t检验和方差分析法对攻毒前后试验动物的相对体质量及试验结束后免疫器官指数进行统计分析,通过比较各组数据的显著性差异来评价复方天门冬多糖注射液对鸡传染性支气管炎的治疗效果。结果显示,复方天门冬多糖注射液能提高发病鸡的相对增量率,并促进发病鸡的生长发育。说明,复方天门冬多糖注射液对患病鸡的临床治疗效果显著,在实际生产中可以推广应用。     

火针层孔菌(桑黄)粗多糖对荷瘤小鼠的免疫调节研究

研究了火针层孔菌不同粗多糖对荷瘤小鼠的免疫调节作用。荷瘤小鼠随机分为四组:胞外粗多糖组、菌丝体粗多糖组、子实体粗多糖组和生理盐水阴性对照组。给药10d后测定荷瘤小鼠脾NK细胞活性和脾淋巴细胞的增殖率。结果显示火针层孔菌粗多糖组与阴性对照组相比能够提高小鼠脾NK细胞活性和脾淋巴细胞的增殖率(P<0.01),表明火针层孔菌液体发酵粗多糖和子实体粗多糖对荷瘤小鼠免疫功能均有调节作用。     

Novel polysaccharide antigen of Orientia tsutsugamushi revealed by a monoclonal antibody

Orientia tsutsugamushi , the causative agent of scrub typhus, is an obligate intracellular bacterium that replicates in the cytosol of host cells. Although several protein antigens have been characterized and cloned, little information exists regarding the polysaccharide antigen of this bacterium. In this study, we identified and characterized a novel antigen defined by a monoclonal antibody (MAb), NT19, against O. tsutsugamushi . Immunofluorescence microscopic studies showed that the NT19 antigen is released from the bacteria in the cytosol of host cells forming aggregates with bacteria. Immunoblot analysis showed that MAb NT19 recognized a strong band with a molecular mass of 20 kDa that was resistant to proteinase K digestion and sensitive to periodate oxidation, suggesting that the NT19 antigen is a polysaccharide. The function of this polysaccharide is not known, but considering its distribution within a bacterial microcolony, it is suspected to be involved in forming a biofilm-like structure within host cells.     

In vitro and in vivo immunomodulatory activity of sulfated polysaccharides from Enteromorpha prolifera

Water-soluble sulfated polysaccharides extracted from Enteromorpha prolifera and fractionated using ion-exchange chromatography (crude, F₁, F₂ and F₃ fractions) were investigated to determine their in vitro and in vivo immunomodulatory activities. The sulfated polysaccharides, especially the F₁ and F₂ fractions, stimulated a macrophage cell line, Raw 264.7, inducing considerable nitric oxide (NO) and various cytokine production via up-regulated mRNA expression. The in vivo experiment results show that the sulfated polysaccharides (the crude and F₂ fractions) significantly increased Con A-induced splenocyte proliferation, revealing their potential comitogenic activity. In addition, IFN-γ and IL-2 secretions were considerably increased by the F₂ fraction without altering the release of IL-4 and IL-5. This implies that the F₂ fraction can activate T cells by up-regulating Th-1 response and that Th-1 cells might be the main target cells of the F₂ fraction. These in vitro and in vivo results suggest that the sulfated polysaccharides are strong immunostimulators.     

Preparation and anticoagulant activity of a fucosylated polysaccharide sulfate from a sea cucumber Acaudina molpadioidea

A fucosylated polysaccharide sulfate, AMP-2, was purified by DEAE-Sepharose Fast Flow and Sephadex G-100 columns in successive steps from a special sea cucumber in southeastern China. HPLC and cellulose acetate membrane electrophoresis experiments confirmed AMP-2 was a homogenous carbohydrate with a relative molecular weight of ca. 2.4 × 10⁴ Da, and methylation analysis indicated that polysaccharide was composed of 1-substituted-Galp, 1,4-disubstituted-GalNp, 1,2-disubstituted-FucSp, 1,4,6-trisubstituted-Glcp in a molar ratio of ca. 0.5:2.0:1.0:3.0, together with a small amount of different substituted Manp. Sulfated derivative and carboxymethylated derivative were prepared using dry pyridine and chlorosulfonic acid, and chloroacetic acid, respectively. Anticoagulant activities in vitro investigation showed that sulfated derivative showed a stronger ability than native polysaccharide and carboxymethylated derivative, which might be caused by their different percentages and types of functional groups in their structures.     

Extracellular polysaccharides of cowpea rhizobia: compositional and functional studies

Polysaccharides excreted by cowpea Rhizobium strains JLn(c) and RA-1 were mixtures of complex acidic exopolysaccharides and low molecular weight neutral glucans. These polymers were fractionated using gel filtration chromatography. Purified fractions of the acidic heteropolymer reacted with peanut agglutinin to give precipitin bands when subjected to Ouchterlony gel diffusion. The acidic exopolysaccharide was found to contain mainly glucose, galactose, glucuronic acid, mannose and fucose. The non-carbohydrate substituents of the acidic heteropolymer were pyruvate, acetate and uronate which were identified by infrared and proton nuclear magnetic resonance spectroscopy as well as by chemical analysis.Abbreviations EPS Extracellular polysaccharide - YEM yeast extract mannitol - PNA peanut agglutination - ¹H-NMR proton nuclear magnetic resonance