细菌表面多糖抗原多样性遗传基础及基因功能分析

目的探讨细菌表面多糖抗原多样性遗传基础及基因功能。方法分别就大肠杆菌、变形杆菌和肺炎链球菌作为研究对象,对表面多糖抗原基因簇多样性的分子进化和遗传基础进行研究。结论在形态上,大肠杆菌和志贺氏菌等肠道杆菌细菌类型均具有丰富多样性,以表面多糖抗原为主要表现。对变形杆菌O抗原基因簇在基因组上的位置进行定位,对其位置的多样性进行验证,并对O抗原基因簇进行分析和测序。在对肺炎链球菌进行研究中,有88种为依赖型,运用质谱技术对单糖合成的酶基因进行鉴定,为其生物学特征和动力学参数的研究打下了基础。

机械化香雪酒发酵过程生物化学成份变化研究

对机械化香雪酒发酵过程生物化学成份变化规律进行了研究;通过对酵母菌总数、酵母形态、细菌总数、细菌形态、还原糖、总酸、挥发酸、酒精度、感官品质、pH等生化指标的定期观察、检测研究;并分离出4株细菌进行糖化发酵试验。经测定:4株细菌有较强的糖化能力,机械化香雪酒的发酵过程细菌也参与糖化作用。结果表明:机械化香雪酒的发酵过程是曲的糖化和以多品种、高密度的细菌糖化发酵与少量酵母发酵协同作用的混合糖化发酵并行的过程(即:边糖化与边细菌糖化发酵、边酵母发酵同时协同进行的三边发酵),酵母数量少、作用小,是真正意义上的细菌为主的发酵。

传统香雪酒发酵过程微生物变化和作用研究

对传统香雪酒发酵过程中的理化变化和微生物变化规律及作用进行了研究;通过对酵母菌总数、酵母形态、细菌总数、细菌形态、还原糖、总酸、挥发酸、酒精度、感官品质、pH等生化指标的定期观察、检测研究;并分离出4株细菌进行了糖化发酵试验,经测定:4株细菌有较强的糖化能力,对饭进行糖化发酵,测得还原糖达100g/L以上,传统香雪酒的发酵过程细菌也参与糖化作用;结果表明:传统香雪酒的发酵过程是曲(酒药、麦曲)的糖化和以多品种、高密度的细菌糖化发酵与酵母糖化发酵协同作用的混合糖化发酵并行的过程,中后期酵母数量少或无,作用小,是真正意义上的细菌为主的发酵。

Separation of growth-stimulating peptides for Bifidobacterium from soybean conglycinin

AIM： To isolate and identify the soybean conglycinin peptides that selectively stimulates the growth of bifidobacteria in vitro, and to investigate the effect of soybean conglycinin peptides on intestinal ecosystem in vivo. METHODS： Soybean conglycinin was purified from soybean seeds by gel filtration （Sepharose-CL-6B）. These proteins were submitted to hydrolysis by pepsin. Several growth-stimulating peptides for bifidobacteria were isolated chromatographically from pepsin hydrolysis of soybean conglycinin and identified by means of matrixassisted laser desorption ionization time of flight mass spectrometry （MALDI-TOF-MS）. Parallel to in vitro study, in vivo experiments with soybean conglycinin peptides were performed in mice. Ninety male KM mice were randomly assigned into five groups of 16 mice each, and each group was administered for 21d intragastrically with physiological saline （control）, conglycinin, pepsin-treated conglycinin （PTC）, the most active fraction which isolated from pepsin-treated conglycinin （P2-PTC） and HCl-full hydrolysis of conglycinin （HCl-FHC）, respectively. Intestinal microflora were evaluated by standard microbiologic methods and biochemical assays of cecal content samples after treatment. RESULTS： The results showed that the peptides which were isolated from soybean conglycinin could stimulate the growth of bifidobacteria in vitro, and the molecular mass of purified peptides with MALDI-TOF-MS ranged from 693.32 to 1829.55. Compared with control group, in vivo experiments showed that P2-PTC group decreased cecal pH （7.08±0.08 vs7.21±0.09, P〈0.05） and enterococcicounts （5.38±0.26 log10CFU/g vs 5.78±0.19 log10CFU/g, P〈0.05）, significantly increased sIgA level （172.08±35.40 ng/g vs 118.27±33.93 ng/g, P〈0.01） and β-galactosidase activity （1.28±0.23 U/g vs 1.82±0.58 U/g, P〈0.05） CONCLUSION： The results have shown that conglycinin is good source for enzyme-mediated production of peptides which stimulate the growth of bifidobacteria. These peptides are inactive within the sequence of the parent protein but can be released during enzymatic hydrolysis, and in vivo experiments demonstrate that conglycinin peptides may be beneficial for improving gastrointestinal health.

Genetic improvement of Trichoderma ability to induce systemic resistance

The beneficial applications of Trichoderma spp. in agriculture include not only the control of plant pathogens, but also the improvement of plant growth, micronutrient availability, and plant tolerance to abiotic stress. In addition, it has been suggested that these fungi are able to increase plant disease resistance by activating induced systemic resistance (ISR) . The mode of action of these beneficial fungi in the Trichoderma -plant-pathogen interaction are many, complex and not completely understood. Numerous lytic enzymes have been characterized, the encoding genes (ech42 gluc78, nag1 from T. atroviride strain P1) cloned, and their role in biocontrol demonstrated. The corresponding biocontrol-related inducible promoters have been used in a reporter system based on the Aspergillus niger glucose oxidase gene (goxA) to monitor biocontrol activity. Glucose oxidase catalyzes the oxygen-dependent oxidation of D-glucose to D-glucono-1,5-lactone and hydrogen peroxide; this latter compound is known to have an antifungal effect and activate the plant defence cascade, thus increasing resistance to pathogen attack. T. atroviride P1 transformants with various promoters gox were tested as seed coating treatments on bean seeds planted in soil infested with a soilborne fungal pathogen. Successively, the emergent leaves were inoculated with a foliar pathogen to determine the effect of the GOX transformants on biocontrol and resistance to pathogen attack. Inoculations with the P1-GOX transformants not only reduced disease symptoms caused by a soil pathogen, but also the lesions of various foliar pathogens applied far from the Trichoderma colonization, thus activating ISR. A similar approach is being use to genetically improve T. harzianum T22, a rhizosphere competent and commercially marketed strain not transformed yet, by using four different gox gene constructs under the control of constitutive and inducible promoters. Plasmids have been introduced in Trichoderma by protoplasts co-transformation. hygromicin resistant progeny selected, and mitotically stable transformants analysed to confirm the presence of the novel enzyme activity. Progenies are being tested for biocontrol ISR inducing activity.

Portulaca oleracea Leaf Aqueous Lyophilized Extract Reduces Hyperglycemia and Improves Antioxidant Status of Red Blood Cells and Liver in Streptozotocin-lnduced Diabetic Wistar Rats

The aim of this study was to investigate the antihyperglycemic and antioxidant effects of Po （Portulaca oleracea） lyophilised aqueous extract in diabetic male Wistar rats. Diabetes was induced intraperitonially by a single injection of STZ （streptozotocin） （60 mg/kg bw （body weight））. Twenty diabetic rats, weighing 263 ± 5 g, were divided into two groups fed a casein diet supplemented or not with Po extract （1 g/kg bw）, for four weeks. Control group （n = 6） received 0.23-0.25 mL of citrate buffer and was fed a standard diet during the experiment. The study was carried out at Oran University, Algeria and the entire experiments lasted from September 2011 to July 2012. Blood was obtained from the abdominal aorta of rats after fasting overnight and standard methods were used for the extraction of spices, determination of glycemia, insulinemia, lipid peroxidation and antioxidant enzymes activities. Portulaca oleracea treated compared to untreated rats, glycemia and HbAIc values were respectively 2.8- and 1.7-fold lower. TBARS （thiobarbituric acid reactive substances） concentrations were reduced in RBC （red blood cells） （-54%） and plasma （-65%）. Moreover, in liver and kidney, TBARS values were respectively 1.8- and 2-fold lower. SOD （superoxide dismutase） and GSH-Px （glutathione peroxidase） activities were increased respectively by ＋38% and ＋85%, in liver. GSSG-Red （glutathione reductase） activity was 1.9-fold higher in kidney, while CAT （catalase） was improved in kidney （＋48%）. In RBCs, SOD, GSH-Px, GSSH-Red and CAT activities were increased by 31%, 42%, 56% and ＋50%, respectively. These data have cast a new light on the actions of Portulaca oleracea and its antioxidant potential benefits in preventing diabetes and its complications.

Insights into bacterial protein glycosylation in human microbiota

The study of human microbiota is an emerging research topic. The past efforts have mainly centered on studying the composition and genomic landscape of bacterial species within the targeted communities. The interaction between bacteria and hosts is the pivotal event in the initiation and progression of infectious diseases. There is a great need to identify and characterize the molecules that mediate the bacteria-host interaction. Bacterial surface exposed proteins play an important role in the bacteria-host interaction. Numerous surface proteins are glycosylated, and the glycosylation is crucial for their function in mediating the bacterial interaction with hosts. Here we present an overview of surface glycoproteins from bacteria that inhabit three major mucosal environments across human body: oral, gut and skin. We describe the important enzymes involved in the process of protein glycosylation, and discuss how the process impacts the bacteria-host interaction. Emerging molecular details underlying glycosylation of bacterial surface proteins may lead to new opportunities for designing anti-infective small molecules, and developing novel vaccines in order to treat or prevent bacterial infection.