铜绿假单胞菌鞭毛功能的影响因素及其致病性

细菌鞭毛是细菌分类的重要依据之一,但近年来人们对鞭毛功能的影响因素很关注,尤其是细菌鞭毛的致病性已成为研究热点.本文讨论了铜绿假单胞菌鞭毛功能的影响因素及其与致病性的关系.     

胃肠微环境下吻合钉仿生表面对细菌黏附的微流场仿真

目的 模拟在吻合钉植入人体以后,吻合钉表面与肠壁组织之间的微流场环境,研究其仿生疏水化表面对细胞外液流速和壁面处流体剪切力的影响,进而通过流场的变化调控细菌的黏附。方法 观察鲨鱼皮肤微结构,建立细菌在微流场环境中的简化二维运动模型。通过计算流体动力学数值仿真,模拟静态流场和动态流场中,细菌分别在光滑表面和微织构表面的运动,比较两种表面环境下细菌周围的流场特征和流体剪切力,分析流体剪切力影响细菌黏附的内在机制。结果 仿生微织构的加入增强了微流场内细胞外液的流速,在静态流场中流体对细菌的黏滞作用较小;动态流场中流体对细菌的推动作用更强;一定范围内的微坑宽度使微织构壁面所受流体剪切力更大。结论 吻合钉的仿生微织构表面,加快了细胞外液的流速,提高了微织构壁面和细菌所受流体剪切力,对细菌的附着有一定影响。研究结果为吻合钉抑菌表面的研究提供了理论依据。     

趋磁性细菌与磁小体的研究与应用(综述)

1975年,美国生物学家Blakemore在试图分离海底泥样中的折叠螺旋体菌时,首次发现了自然界存在的一类奇特的微生物——趋磁性细菌(magnetotactic bacterium)。趋磁性细菌是一类能够沿着磁力线运动的特殊细菌,其体内含有对磁场具有敏感性的磁小体(magnetosomes),起了导向的作用,并借助于自身的鞭毛来运动。这     

新闻点击

科学家发现钙原子是控制细菌运动的关键据美国BIOCOMPARE科技新闻网(2010-02-04)报道,细菌能利用鞭毛(flaggella)在水溶液的环境下游动,也能利用形态较为细小的纤毛(pili)进行漫步或行走的动作,这些细菌的运动行为也是一些致病菌能造成感染的原因之一,导致人们生病甚至死亡。最近,美国北卡大学(the University of North Carolina)的研究人员发现,钙(calcium)原子与细菌的运动行为有很     

细菌鞭毛镀银染色法的创新

目的 发明一种新的细菌鞭毛镀银染色方法。方法 染色媒染剂由A、B2种溶液组成，A液是酸化的FeCl3溶液，B液是含有甲醛的丹宁酸溶液，A、B液混合后，微加热，染涂片50s，洗净涂片后镀银染色。共有19属34种228株细菌，每株菌都进行固体培养和液体培养进行鞭毛染色，并采用West氏评分法对鞭毛染色质量进行评价。结果 鞭毛形态及其在菌体的位置极易观察。228株细菌获得良好的鞭毛染色质量，血琼脂平板培养平均每株菌获得4．7分，肉汤培养获得4．6分。与一些肠杆菌株不同，100株非发酵菌血琼脂平板培养鞭毛染色均获得5分，而99株肠杆菌肉汤培养鞭毛染色获得4分以上。一些弧菌科细菌鞭毛位置分布因这2种培养方法的不同而有差异。并发现1株非O1群霍乱弧菌有单侧毛和亚极端毛。结论 这种鞭毛染色方法操作简单、快速，试剂稳定，重复性好。由于可靠性好，可以作为常规方法。非发酵菌适合于固体培养进行鞭毛染色获得最佳效果，液体培养对于一些肠杆菌鞭毛染色更为适合。     

趋化因子在树突状细胞和T细胞迁移活化中的作用和意义

趋化因子是机体内一群能使细胞发生趋化运动的细胞因子 ,通过与表达于细胞表面的趋化因子受体结合而发挥其生物学作用。树突状细胞是一种专职的抗原递呈细胞。树突状细胞的成熟和功能与趋化因子和其受体介导的体内迁移密切相关 ,从而有效的将抗原递呈给初始T细胞并使之活化和分化 ,发挥其调节免疫应答的作用。     

CD44介导的透明质酸对单核细胞黏附和迁移的作用

目的研究透明质酸（HA）在单核细胞中的分布,HA受体CD44和细胞问黏附分子-1（ICAM-1）在单核细胞中的表达以及HA及其受体对单核细胞黏附和迁移的影响.方法用Percoll非连续密度梯度离心法分离狗外周血单核细胞,然后用免疫荧光染色法标记单核细胞的HA、CD44和ICAM-1.通过用透明质酸酶（HAase）消化细胞表面的HA、在培养皿底面和细胞培养池膜上涂布HA和在培养液中添加HA,观察细胞表面的HA、底物HA和游离HA对细胞黏附和迁移的影响.以抗体阻断剂抑制CD44或ICAM-1,研究HA受体的介导作用.结果单核细胞表面和细胞内存在HA,并表达CD44和ICAM-1.消化细胞表面HA后,黏附和迁移的单核细胞数减少.在培养皿底面和细胞培养池膜上铺HA,黏附和迁移的细胞数增加.培养液中加入HA,黏附和迁移的细胞数减少.阻断CD44后,HA底物上黏附和迁移的细胞数减少,而阻断ICAM-1后黏附和迁移的单核细胞数无明显变化.结论单核细胞内外分布有HA.单核细胞表面的HA和底物HA促进细胞的黏附和迁移,但游离HA阻碍单核细胞的黏附和迁移.CD44介导HA对单核细胞黏附和迁移的作用.     

神经元与胶质细胞的相互作用

<正> 在中枢神经系统的发育过程中,神经元沿着星状胶质细胞突起从特定的增生区迁移到目标区。小脑的分裂后期的颗粒细胞沿Bergmann胶质细胞突起从外颗粒层穿过分子层及Purkinje细胞层迁移到内颗粒层。神经元沿胶质细胞突起运动的机理可能与凝集素及细胞表面的糖蛋白有关。Lehimann近来报导用抗内源性小脑凝集素抗体及凝素集结合糖蛋白抗体处理小脑培养物可抑制颗粒细胞的迁移活动。他们推测可溶性的凝集素可在神经元及星状胶质细胞间形成一种“桥”,而细胞表面凝集素结合糖蛋白则介导凝集素“桥”的形成。这个“桥”的形成支持细胞粘连,这对胶质细胞介导的神经元运动有意义。Stitth及Hatten发现星状胶质细胞抑制素(astrostactin),为一种细胞糖蛋白,可抑制小脑颗粒细胞与星状胶质细胞的粘连,但不抑制神经元间的粘连。     

趋化因子在树突状细胞和T细胞迁移活化中的作用和意义

趋化因子是机体内一群能使细胞发生趋化运动的细胞因子，通过与表达于细胞表面的趋化因子受体结合而发挥其生物学作用。树突状细胞是一种专职的抗原递呈细胞。树突状细胞的成熟和功能与趋化因子和其受体介导的体内迁移密切相关，从而有效的将抗原递呈给初始T细胞并使之活化和分化，发挥其调节免疫应答的作用。     

微流控脓毒症患者中性粒细胞惯性无标记分选及趋化性研究

脓毒症患者中性粒细胞（PMN）的趋化迁移能力减弱,导致细菌清除率下降,加速了脓毒症病程的发展。对脓毒症患者PMN的趋化性进行量化,有助于表征脓毒症患者的免疫健康状况。微流控芯片具有试剂消耗低、近生理环境、迁移过程可视化等优点,被广泛用于细胞趋化性分析。目前,采用微流控芯片进行PMN趋化性的研究,主要受限于细胞分离操作繁琐和微流控芯片通量低。本文首先设计了一款惯性细胞分选芯片,利用白细胞（主要包括粒细胞、淋巴细胞和单核细胞）和红细胞在螺旋微通道中运动时,会受到不同大小惯性力和迪恩阻力的作用,而移动至螺旋微通道的不同位置聚焦这一基本原理,实现两大类细胞无标记分离。随后,本文设计了多通道细胞迁移芯片,构建了微流控PMN惯性无标记分选及趋化性分析平台,惯性细胞分选芯片分离出白细胞群后注入多通道细胞迁移芯片,可在15 min内完成PMN对趋化肽（fMLP）的趋化性测试。其余细胞,如单核细胞运动缓慢、淋巴细胞需要预先激活与增殖培养,而不会发生明显趋化迁移现象。本研究招募的脓毒症患者（n=6）和健康志愿者（n=3）测试结果表明,脓毒症患者PMN的趋化性指数（CI）和迁移速度（v）明显弱于健康志愿者。...     

Improving the reproducibility of Pseudomonas aeruginosa swarming motility assays

Swarming motility is a rapid and coordinated migration of a bacterial population across a semi-solid surface. This multicellular phenomenon is getting increasing attention as it is suspected to be related to biofilm development of Pseudomonas aeruginosa. Published swarm plate preparation protocols differ greatly from one study to another and no reproducible and standardized protocols have been proposed to accurately study this phenomenon. We report here a rapid and highly reproducible swarm plate protocol for P. aeruginosa and show how different key parameters affect this type of motility (i.e. agar %, drying time under laminar flow, incubation temperature and pH). Results reported here will help to standardize swarming motility assays and develop effective swarm plate protocols for other bacterial species.     

Characterization of the dapA-nlpB genetic locus involved in regulation of swarming motility, cell envelope architecture, hemolysin production, and cell attachment ability in Serratia marcescens

Swarming migration of Serratia marcescens requires both flagellar motility and cellular differentiation and is a population-density-dependent behavior. While the flhDC and quorum-sensing systems have been characterized as important factors regulating S. marcescens swarming, the underlying molecular mechanisms are currently far from being understood. Serratia swarming is thermoregulated and is characterized by continuous surface migration on rich swarming agar surfaces at 30 degrees C but not at 37 degrees C. To further elucidate the mechanisms, identification of specific and conserved regulators that govern the initiation of swarming is essential. We performed transposon mutagenesis to screen for S. marcescens strain CH-1 mutants that swarmed at 37 degrees C. Analysis of a "precocious-swarming" mutant revealed that the defect in a conserved dapA(Sm)-nlpB(Sm) genetic locus which is closely related to the synthesis of bacterial cell wall peptidoglycan is responsible for the aberrant swarming phenotype. Further complementation and gene knockout studies showed that nlpB(Sm), which encodes a membrane lipoprotein, NlpB(Sm), but not dapA(Sm), is specifically involved in swarming regulation. On the other hand, dapA(Sm) but not nlpB(Sm) is responsible for the determination of cell envelope architecture, regulation of hemolysin production, and cellular attachment capability. While the nlpB(Sm) mutant showed similar cytotoxicity to its parent strain, the dapA(Sm) mutant significantly increased in cytotoxicity. We present evidence that DapA(Sm) is involved in the determination of cell-envelope-associated phenotypes and that NlpB(Sm) is involved in the regulation of swarming motility.     

Swarming motility in Bradyrhizobium japonicum

Flagellar-driven bacterial motility is an important trait for colonization of natural environments. Bradyrhizobium japonicum is a soil species that possesses two different flagellar systems: one subpolar and the other lateral, each with a filament formed by a different set of flagellins. While synthesis of subpolar flagellins is constitutive, translation of lateral flagellins was detected in rhizobia grown with l-arabinose, but not with d-mannitol as sole carbon source, independently of whether bacteria were in liquid or semisolid medium. We characterized swarming of B. japonicum in semisolid medium and found that this motility was faster with l-arabinose than with d-mannitol. By using mutants with deletions in each flagellin set, we evaluated the contribution of each flagellum system to swarming in semisolid culture media, and in soil. Mutants devoid of either of the flagella were affected in swarming in culture media, with this impairment being stronger for mutants without lateral flagella. In sterile soil at 100% or 80% field capacity, flagellar-driven motility of mutants able to swim but impaired in swarming was similar to wild type, indicating that swimming was the predominant movement here.     

Ultrastructure of Proteus mirabilis swarmer cell rafts and role of swarming in catheter-associated urinary tract infection

Proteus mirabilis is a common cause of catheter-associated urinary tract infection (C-UTI). It blocks indwelling urethral catheters through the formation of extensive crystalline biofilms. The obstruction of urine flow can induce episodes of pyelonephritis, septicemia, and shock. P. mirabilis exhibits a type of motility referred to as swarming, in which multicellular rafts of elongated, hyperflagellated swarmer cells form and move rapidly in concert over solid surfaces. It has been suggested that swarming is important in the pathogenesis of C-UTI. In this study we generated a set of stable transposon mutants deficient in swarming and used them to assess the role of swarming in the migration of P. mirabilis over urinary catheters. Swarming was found to be essential for migration over all-silicone catheters. Swarming-deficient mutants were attenuated in migration over hydrogel-coated latex catheters, but those capable of swimming motility were able to move over and infect these surfaces. A novel vapor fixation technique for the preparation of specimens and scanning electron microscopy were used to resolve the ultrastructure of P. mirabilis multicellular rafts. The flagellar filaments of P. mirabilis were found to be highly organized during raft migration and were interwoven in phase to form helical connections between adjacent swarmer cells. Mutants lacking these novel organized structures failed to swarm successfully. We suggest that these structures are important for migration and formation of multicellular rafts. In addition, the highly organized structure of multicellular rafts enables P. mirabilis to initiate C-UTI by migration over catheter surfaces from the urethral meatus into the bladder.     

Population cell differentiation of Serratia marcescens on agar surface and in broth culture

The bacterium Serratia marcescens shows population surface migration (swarming) phenomenum on an LB swarming plate, and differentiated cells can be observed at the swarming front. How the cell population differentiates during swarming on the agar surface is not known, neither is it clear whether cells with differentiated characteristics can be observed in broth culture. To monitor the population cell differentiation in a highly sensitive way without cell destruction, experiments were designed using bacterial luciferase genes luxAB as the reporter genes to allow direct monitoring of the differentiating cells through bioluminescence. An isogenic S. marcescens strain was constructed with luxAB under the control of the promoter of flagellin gene hag (phag::luxAB). Patterns of cell differentiation were monitored either by direct X-ray film exposure and/or by Autolumat luminometer detection. Results show that population cell differentiation on the agar surface occurs first in a temporal and then spatial way during colonial growth. It was also found that cells harvested from both the spreading agar plate and broth culture showed differentiation patterns similar to those from swarming cells, suggesting that the agar surface culture may not be essential for the formation of differentiated cells.     

Measurement of Proteus cell motility during swarming.

The motilities of Proteus long forms during swarming on agar were measured on cells transferred to liquid suspension. During concentric-ring formation on solid medium, when the edge of the swarm was advancing slowly or had stopped, the velocity of long-form motility was low. When the colony was spreading rapidly, long-form velocitywas relatively high. This periodic variation in cell velocity, which determines the zones formed during swarming, cannot adequately be explained by negative chemotaxis.     

观察铜绿假单胞菌pvdQ基因对群集游动中抗生素抗性的影响

目的 探讨铜绿假单胞菌pvdQ(PA2385)基因在群集游动中对几种常用抗生素抗性的影响.方法 构建pvdQ基因表达质粒pME6032-pvdQ并鉴定,采用电穿孔法将带有pvdQ基因的质粒转入PAO1中,构建pvdQ高表达株.同时将空质粒pME6032采用电穿孔法转入PAO1中,构建pME6032空质粒株.在不同浓度抗生素中,通过比较群集游动直径的大小,观察PAO1和pvdQ高表达株对抗生素抗性的改变.结果 经鉴定成功构建pvdQ高表达株,比较两株菌群集游动直径大小:抗生素浓度成倍增加,但群集游动直径不是成倍下降而是成不规则增加,说明PAO1和pvdQ高表达株均能提高抗生素抗性;pvdQ高表达株对头孢他啶、环丙沙星、美罗培南和多黏菌素B几种抗生素与PAO1相比抗性提高了2～4倍.结论 铜绿假单胞菌pvdQ高表达株能够提高抗生素的抗性,说明pvdQ基因在此过程中发挥重要作用,可能通过参与群集细胞的分化来提高抗生素的抗性.

Abstract：

Objective To investigate whether Pseudomonas aeruginosa pvdQ( PA2385 ) gene reveals altered antibiotic susceptibility under swarming conditions. Methods The plasmid pME6032 with pvdQ gene was constructed and identified, then transformed into Pseudomonas aeruginosa PAO1 by the electroporation, building pvdQ overexpression strain. Using the same method building pME6032-PAO1 strain.Bacteria were inoculated in LB overnight , measuring the colony diameter of the swarming zone . Results Strains of pvdQ overexpression was successfully constructed by real-time PCR. Comparison of two strains of the swarming motility of change in diameter: The result showed that PAO1 and pvdQ overexpression strains can both improve the antibiotics resistance. Swarmer cells of pvdQ overexpression strain exhibited a 2- to 4-fold increase in antibiotic resistance toward ceftazidime,ciprofloxacin, meropenem and polymyxin B compared to PAO1 on BM2-swarming agar plates. Conclusion pvdQ gene played an important role in elevating the antibiotics resistance, which through prarticipated in the swarmer cell differentiation.     

The use of host cell machinery in the pathogenesis of Listeria monocytogenes

The bacterial pathogen, Listeria monocytogenes, exploits the host cell's machinery, enabling the pathogen to enter into cells and spread from cell to cell. Three bacterial surface proteins are crucial for these processes: internalin and InlB, which mediate entry into cells, and ActA, which induces actin polymerisation at one pole of the bacterium and promotes intracellular and intercellular motility. Recent studies have identified several of the cellular factors involved in the entry process and major discoveries have unravelled the mechanisms underlying the actin-based motility. Increasing evidence shows that many cellular genes are up- or down-regulated during infection and probably play a role in the establishment of infection, inflammation and induction of the host immune response.