末端酶在噬菌体包装过程的作用

噬菌体是病毒的一种,专以细菌为宿主,主要通过吸附、侵入、生物合成、装配、释放5个步骤进行,具有独特的核酸成熟和包装机制。随着抗生素的滥用,各种"超级细菌"已经出现,噬菌体治疗是代替抗生素类生物物品的热点之一。本文主要介绍了噬菌体的位点特异性包装、满头包装两种包装致病机制,及末端酶在这两种包装机制中发挥的重要作用,为研发新的生物药品提供新思路。     

细菌胞外囊泡与宿主的互作机制研究进展

细菌胞外囊泡（BEVs）是一类由细菌分泌的可携带和转运各种物质的纳米级颗粒,在母源细菌与宿主互作中发挥重要作用。研究发现,BEVs可携带母源细菌源抗原成分参与免疫反应信号通路,实现对宿主的免疫调节作用,为疫苗开发提供了新思路;肠道中的BEVs可刺激黏蛋白产生,增强肠道屏障效应、降低肠道炎症,既能作为修复肠炎患者肠道屏障功能的潜在药物,也可作为评估肠道损伤情况的标志物;BEVs还可通过调节糖和脂质代谢的信号通路调节宿主代谢。反过来,宿主也能影响细菌及其BEVs的分泌。本文综述了BEVs的组成及其在宿主免疫调节、肠道屏障功能和代谢过程中作用机制,以期为BEVs在临床和生产应用中提供参考。     

细菌鞭毛运动、黏附和免疫逃逸机制的研究进展

鞭毛是细菌表面重要的附属结构之一,很长一段时间以来被认为仅负责细菌的运动。然而随着对鞭毛的结构以及致病性深入研究发现,鞭毛的运动性能够促进细菌与宿主的相互作用,鞭毛介导的黏附在几种动植物病原体对宿主的定植过程中起很重要作用,而促进鞭毛结合到不同宿主组织的特异性互作机制至今仍不清楚。鞭毛素单体的保守区是机体先天性免疫应答的有效诱导剂,能够诱导机体发生免疫应答,然而细菌也进化出多重策略来逃避免疫识别。现对近年来细菌鞭毛在动植物宿主环境中的作用作一综述,为更全面认识和研究鞭毛提供参考。     

中国农业科学院哈尔滨兽医研究所——基础免疫创新团队

<正>研究内容1.高致病性猪繁殖与呼吸综合征病毒(HP-PRRSV)-细菌混合感染致病力增强分子机制研究:建立HP-PRRSV-细菌混合感染动物或细胞模型,研究病毒-细菌混合感染导致炎症反应增强和动物死亡增加的分子机制。2.利用基因敲除小鼠为模型,研究病毒、细菌及寄生虫感染后逃逸宿主天然免疫的分子机制。3.寻找具有抑制慢病毒复制活性的宿主限制性因子,研究慢病毒和宿主相互作用的分子机制。理解这些限制性因子的抗病毒活性将有助于发现新型的抗病毒分子机制和开发新的抗病毒治疗方法。     

噬菌体与动物细胞的相互作用

噬菌体是动物体内最丰富的生物群体。噬菌体易获得、宿主特异性强、不易产生耐药性等特点使其在治疗耐药细菌感染方面具有很大优势。随着基因工程和显微镜技术的发展，噬菌体对动物细胞的调节机制逐渐被发现。笔者综述了近年来关于噬菌体进入动物细胞的机制、噬菌体在细胞内的分布及与细胞内受体相互作用的研究进展，强调了噬菌体在协助宿主细胞杀灭细菌过程中的作用，讨论了噬菌体与动物细胞相互作用对噬菌体治疗的意义，旨在为噬菌体治疗耐药细菌的研究提供理论基础。     

细菌细胞壁肽聚糖的研究进展

肽聚糖(PG)是细菌细胞壁成分, 大部分革兰氏阳性菌及部分革兰氏阴性菌细胞壁都含有PG.PG具有多种生物学活性,在调节宿主免疫功能方面发挥着重要作用.本文综述了细菌细胞壁PG的结构与分类、分离纯化、生物合成、代谢过程、生物学功能、免疫作用机制及应用前景.     

浅谈反刍动物粗饲料中含氮物的利用

随着反刍动物瘤胃生理和生化过程的研究和发展,人们已经揭示出了瘤胃氮代谢的基本规律以及瘤胃微生物(细菌、纤毛虫和原虫)有利用非蛋白氮(NPN)合成细菌蛋白质以供宿主动物利用方面的作用机制和影响因素。在此基础上,已经开始制定出新     

NDRVσC蛋白互作的宿主因子筛选及生物信息学分析

研究鸭呼肠孤病毒(Duck reovirus,DRV)σC蛋白与宿主因子之间的相互作用,对揭示σC蛋白在病毒复制过程中的功能及该病毒的致病机理具有重要作用。本研究采用免疫共沉淀法及质谱分析技术,筛选出与σC蛋白可能发生互作的宿主相关蛋白,并对所筛选出的宿主细胞蛋白进行了GO注释和KEGG代谢通路注释。结果表明,与空白对照组比较,获得与σC蛋白相互作用的宿主细胞蛋白有100个;筛选出的这些宿主细胞蛋白中,在病毒感染后不同时间点差异表达量均上升3倍以上的蛋白有6个,分别与病原致病性、蛋白质代谢途径、细胞信号通路转导有关。该研究结果为进一步探讨σC蛋白的生物学功能奠定了基础,也为揭示σC蛋白与宿主因子相互作用进而调控DRV复制等机制研究提供线索。     

马链球菌兽疫亚种SeseC-00619蛋白的功能研究

为了阐明马链球菌兽疫亚种新蛋白SeseC-00619(细胞表面蛋白,cell surface protein,CSP)的功能,本试验采用real-time qPCR分析CSP的体内诱导表达特征,同时在大肠埃希菌中表达与纯化马链球菌兽疫亚种表面相关蛋白CSP,研究其免疫反应性及免疫保护功能,并试图解释其分子机制。通过流式细胞术与黏附抑制试验探索CSP对小鼠肺上皮细胞的黏附作用。结果表明,CSP是一个重要的体内诱导抗原,并且能在S.zooepidemicus细菌表面表达,属于细菌表面蛋白。重组蛋白CSP能够黏附LA-4细胞表面,而这种黏附作用可以竞争性抑制S.zooepidemicus黏附宿主细胞。本结果为进一步研究CSP基因的功能及其在致病机制中的作用奠定了基础。     

瘤胃微生物与宿主的互作及其对瘤胃上皮发育的影响

瘤胃上皮在挥发性脂肪酸的吸收和代谢中发挥着重要作用，但瘤胃上皮发育的机制尚不清楚。近年来研究报道，瘤胃微生物与宿主存在互作关系，瘤胃微生物可以通过与宿主的相互作用，在瘤胃上皮发育和代谢中发挥作用。然而，瘤胃微生物与宿主相互作用的调节机制在很大程度上是未知的。因此，本文总结了瘤胃微生物与宿主互作以及其促进瘤胃上皮发育的最新研究成果，以期从瘤胃微生物与宿主互作角度，分析瘤胃上皮发育机制，为进一步了解瘤胃上皮发育过程中瘤胃微生物与宿主之间的关系研究提供理论依据。     

Advances on the Biosynthesis Mechanism of Bacterial Polysaccharides

Polysaccharide is the major component of bacterial cell that plays a significant role in the interaction between bacteria and their hosts. It aids the identification of bacteria, imparting virulence to the bacteria and adjusting host's immune response as well. Advance genomics research has deciphered several different bacterial polysaccharides sharing a common biosynthesis mechanism. The study of polysaccharides is mainly based on sequence analysis and prediction of genome in combination with metabolite analyses that still requires a detailed study. Researchers are now further focusing on their biosynthetic pathways to unveil the mechanisms underlying the diversity of these bacterial polysaccharides along with the host-pathogen interaction. It will open new doors for vaccine development and other therapeutic methods against pathogenic bacteria, and also provide technical support to control disease and cure at molecular level. This review states the mechanisms and relevant problems of biosynthesis and in vitro biosynthesis of peptidoglycan,O-antigen and capsular polysaccharides,and summarizes the application of bacteria polysaccharides in the aspects of searching for candidate antigens and controlling the targets of pathogenic bacteria and exploring genetic evolution of bacteria and biological synthesis.     

Intestinal bacterial overgrowth includes potential pathogens in the carbohydrate overload models of equine acute laminitis

Carbohydrate overload models of equine acute laminitis are used to study the development of lameness. It is hypothesized that a diet-induced shift in cecal bacterial communities contributes to the development of the pro-inflammatory state that progresses to laminar failure. It is proposed that vasoactive amines, protease activators and endotoxin, all bacterial derived bioactive metabolites, play a role in disease development. Questions regarding the oral bioavailability of many of the bacterial derived bioactive metabolites remain. This study evaluates the possibility that a carbohydrate-induced overgrowth of potentially pathogenic cecal bacteria occurs and that bacterial translocation contributes toward the development of the pro-inflammatory state. Two groups of mixed-breed horses were used, those with laminitis induced by cornstarch (n=6) or oligofructan (n=6) and non-laminitic controls (n=8). Cecal fluid and tissue homogenates of extra-intestinal sites including the laminae were used to enumerate Gram-negative and -positive bacteria. Horses that developed Obel grade2 lameness, revealed a significant overgrowth of potentially pathogenic Gram-positive and Gram-negative intestinal bacteria within the cecal fluid. Although colonization of extra-intestinal sites with potentially pathogenic bacteria was not detected, results of this study indicate that cecal/colonic lymphadenopathy and eosinophilia develop in horses progressing to lameness. It is hypothesized that the pro-inflammatory state in carbohydrate overload models of equine acute laminitis is driven by an immune response to the rapid overgrowth of Gram-positive and Gram-negative cecal bacterial communities in the gut. Further equine research is indicated to study the immunological response, involving the lymphatic system that develops in the model.     

Immunobiology of bovine mammary gland: apoptosis of somatic cells in milk during naturally occurring mastitis

Mastitis remains a major cause of economic losses in dairy herds. It is believed, that the enhancement of natural defense mechanisms in mammary gland may be helpful in the treatment of bovine mastitis. Our study was designed to assess the apoptosis of leukocytes isolated from bovine milk during subclinical staphylococcal mastitis. Milk samples were collected from cows naturally infected with one pathogen--Staphylococcus aureus and from animals with mastitis caused by several pathogens, including S. aureus. It has been determined that the rate of apoptosis was lower in mastitic milk, as compared with control samples, although varied significantly between groups. High percentage of apoptotic cells was detected in milk with high counts of pathogenic bacteria. In all groups the rate of apoptosis was dependent on the bacterial load, although various correlations were identified. Thus, it is postulated, that the rate of apoptosis of somatic cells in mastitic milk is related to the etiology of infection and is determined by the bacterial load.     

Probiotic alternatives to reduce gastrointestinal infections: the poultry experience

The intestinal mucosa represents the most active defense barrier against the continuous challenge of food antigens and pathogenic microorganisms present in the intestinal lumen. Protection against harmful agents is conferred by factors such as gastric acid, peristalsis, mucus, intestinal proteolysis, and the intestinal biota. The establishment of beneficial bacterial communities and metabolites from these complex ecosystems has varying consequences for host health. This hypothesis has led to the introduction of novel therapeutic interventions based on the consumption of beneficial bacterial cultures. Mechanisms by which probiotic bacteria affect the microecology of the gastrointestinal tract are not well understood, but at least three mechanisms of action have been proposed: production/presence of antibacterial substances (e.g., bacteriocins or colicins), modulation of immune responses and specific competition for adhesion receptors to intestinal epithelium. The rapid establishment of bacterial communities has been thought to be essential for the prevention of colonization by pathogenic bacteria. Some animal models suggest that the reduction in bacterial translocation in neonatal animals could be associated with an increase in intestinal bacterial communities and bacteriocin-like inhibitory substances produced by these species. This review emphasizes the role of the intestinal microbiota in the reduction of the gastrointestinal infections and draws heavily on studies in poultry.     

Role of Ichthyophthirius multifiliis in the Infection of Aeromonas hydrophila

Aeromonas hydrophila and Ichthyophthirius multifiliis are important fish pathogens. To clarify their relationship, two host models, goldfish with trauma and those infected with I. multifiliis, were used to study infection kinetics of A. hydrophila 4332 tagged with plasmid pGFPuv (Ah4332(GFP)). The results showed that in fish suffering from ichthyophthiriosis, the bacterial infection process was accelerated and more persistent than in the other groups. It is suggested that I. multifiliis plays an important role in the infection of A. hydrophila. Mechanical trauma caused by I. multifiliis might act as a portal of entry for A. hydrophila present in the water, thereby facilitating the invasion of bacteria. The ectoparasite might also serve as a vector and reservoir of pathogenic bacteria.     

桑树病原原核生物及其病害的研究进展(Ⅰ)

侵染桑树的病原原核生物有细菌、菌原体、螺原体、立克次体等,其中由病原细菌引发的桑树细菌病害对蚕桑生产的危害极大。主要介绍原核生物界薄壁菌门的病原细菌侵染桑树导致的桑疫病、桑青枯病、桑枝软腐病、桑枯萎病和桑叶斑病等重要桑树细菌病害,从病原及其侵染循环,桑树发病规律、发病症状,病害防治方法几个方面概述其研究进展。     

脂多糖修饰对革兰阴性菌毒力及外膜囊泡生物学特性影响的研究进展

脂多糖(LPS)是革兰阴性(G^-)菌的内毒素,刺激机体引发炎症反应,为细菌的一种毒力因子,主要存在于细菌细胞壁外膜上,也是外膜囊泡(OMVs)的主要成份。OMVs是细菌从膜上脱落下来的一种囊状结构,含有大量的LPS、外膜蛋白及其他成分,具有良好的免疫原性,被认为是最具潜力的亚单位疫苗。大多数LPS由类脂A、核心寡糖和O抗原多糖组成,这3个组分的合成影响着LPS的结构,继而影响细菌的毒力和细菌分泌OMVs的产量、毒性及免疫原性等生物学特性。论文主要对LPS的合成转运过程中结构修饰对G^-菌毒力及其OMVs生物学特性的影响进行综述,为革兰阴性菌致病机理研究及开发新型亚单位疫苗提供新思路。     

曲靖地区仔猪腹泻细菌性病原的分离鉴定与耐药性分析

为了解曲靖地区仔猪出现腹泻的细菌性病因,对5个养殖场148份出现仔猪腹泻症状的样品进行细菌分离培养及耐药性分析,结果显示,检出致病性大肠杆菌(E.coli)114份,阳性率为77.03%;沙门氏菌(Salmonella)26份,阳性率为17.57%,混合感染率为17.57%.致病性大肠杆菌和沙门氏菌对多种抗生素产生了耐药性,其中114株致病性大肠杆菌中97株呈多重耐药性,占总菌数的85.09%,26株沙门氏菌中20株呈多重耐药性,占总菌数的76.92%.结果表明,致病性大肠杆菌是导致当地哺乳仔猪腹泻的主要细菌性病原,部分仔猪继发感染沙门氏菌,两种细菌对多种抗生素产生了耐药性,多重耐药现象较严重.     

Presence of Bacteria on the External Genitalia of Healthy Stallions and its Transmission to the Mare at the Time of Breeding by Live Cover

The current field study used thoroughbred stallions and mares from central Kentucky to investigate the occurrence of potentially pathogenic bacteria on the stallion's external genitalia, based on cultures, and investigated the occurrence of bacteria and type of isolate in the mare's uterus after breeding by live cover to stallions with or without positive bacterial cultures. Fifteen thoroughbred stallions and 206 mares from two central Kentucky thoroughbred farms were used during the 2010 and 2011 breeding seasons. Samples for bacteriological evaluation were taken from the prepuce and postejaculate urethra (n = 201) of stallions. Uterine swabs (n = 264) were collected 12-18 hours postbreeding. For statistical analyses, a chi-squared test was used to test the relationship between stallion culture results and postbreeding uterine culture results, as well as the effect of bacterial types found on the stallion cultures with bacterial types found on the postbreeding uterine cultures. Of stallion cultures, 22.4% were positive for potentially pathogenic bacteria, with Streptococcus equi subspecies zooepidemicus (51.1%) being the most common isolate. Uterine cultures resulted in a 29.2% positive rate for potentially pathogenic bacteria, with S. equi subsp. zooepidemicus (90.9%) being the most common. There was no difference (P > .05) in the occurrence of bacteria or type of isolate found on uterine cultures after breeding stallions with or without positive cultures. In conclusion, potentially pathogenic bacteria found on the stallion's external genitalia did not affect the occurrence and type of bacterial isolate found in the mare's uterus after breeding by live cover.     

金黄色葡萄球菌氟喹诺酮的耐药抑制剂研究进展

金黄色葡萄球菌是引起人和动物感染的一种重要病原菌,它可以对氟喹诺酮等多种抗菌药物产生耐药性,严重影响临床治疗效果。NorA蛋白介导的药物主动外排成为葡萄球菌对氟喹诺酮类药物耐药的重要机制,利血平等作为NorA外排蛋白抑制剂,可有效降低其耐药性的产生。CCCP等能量抑制剂可加强细菌对氟喹诺酮类药物的摄取量。文章从葡萄球菌对氟喹诺酮类药物耐药机制、耐药抑制剂作用途径和能量抑制剂影响等方面,简要介绍金黄色葡萄球菌氟喹诺酮的耐药抑制剂研究进展。