Bacteria adhesion and biofilms on surfaces

Bacterial adhesion has become a significant problem in industry and in the domicile, and much research has been done for deeper understanding of the processes involved. A generic biological model of bacterial adhesion and population growth called the bacterial biofilm growth cycle, has been described and modified many times. The biofilm growth cycle encompasses bacterial adhesion at all levels, starting with the initial physical attraction of bacteria to a substrate, and ending with the eventual liberation of cell clusters from the biofilm matrix. When describing bacterial adhesion one is simply describing one or more stages of biofilm development, neglecting the fact that the population may not reach maturity. This article provides an overview of bacterial adhesion, cites examples of how bacterial adhesion affects industry and summarises methods and instrumentation used to improve our understanding of the adhesive properties of bacteria.     

MWCNT-PEI对细菌菌膜生长和结构的影响

菌膜是细菌适应周围环境的重要生存模式，在调控地球物质循环方面发挥着积极作用.碳纳米材料由于其独特的理化性质，在多个领域得到广泛应用.这些材料释放到环境中是否会影响菌膜生长和结构的变化，成为纳米毒理学领域的前沿热点.文章合成了一种接枝聚乙烯亚胺的多壁碳纳米管（MWCNT-PEI），具有良好的分散性、稳定性，以及优异的抗菌能力.同时，MWCNT-PEI会改变菌膜的生长周期和成熟菌膜结构组分，即刺激细菌分泌更多的胞外多聚物基质（EPS）.文章可为评估碳纳米材料的环境风险提供理论指导，也可为调控菌膜生长和结构提供新思路.     

流动室系统中含氮杂环化合物降解菌的生物膜形成特征研究

采用流动室(Flow Cell)生物膜发生装置和激光共聚焦显微镜观察技术, 揭示不同环境条件下含氮杂环化合物(nitrogenous heterocyclic compounds, NHCs)降解菌的生物膜形成特征。结果表明, 增加初始接种菌液浓度并延长初始黏附时间, 有利于吡啶降解菌在基质表面的黏附和生物膜形成; 降低培养基流速, 细菌生物膜更加均质化且形成水通道结构; 不同条件下的生物膜都存在内层活细胞比例较低, 外层活细胞比例较高的规律。此外, 还发现相对于单一菌株, 混合菌株在生物膜厚度、基质覆盖率与活细胞比例上都更具优势。目标NHC浓度对喹啉降解菌生物膜的形态和活性也有明显的影响: 低浓度下降解菌团聚结构分布较零散, 但具有较大的体积; 高浓度下降解菌团聚结构明显变小, 在基质表面的分布则更均匀; 低浓度下生物膜的活细胞比例显著高于高浓度下的生物膜。     

环二鸟苷酸对细菌运动调控的研究进展

细菌中的第二信使环二鸟苷酸(c-di-GMP)对细菌的运动性有调节作用.c-di-GMP调控鞭毛的生物合成、菌毛形成和菌毛蛋白的组成,以及其他一些与运动相关的蛋白的合成.细菌的运动性与其毒力、致病性、粘附性、趋化性、生物膜组成等密切相关.在革兰氏阴性细菌中,关于c-di-GMP的信号通路的研究较为清晰,而在革兰氏阳性细菌中,关于该信号转导通路的研究较少.此外,有关c-di-GMP的信号通路的研究主要集中在病原菌.该文主要综述了一些常见病原菌中c-di-GMP对其运动性的调控机制,为研究其他细菌c-di-GMP信号通路提供思路.     

A component of innate immunity prevents bacterial biofilm development

Antimicrobial factors form one arm of the innate immune system, which protects mucosal surfaces from bacterial infection. These factors can rapidly kill bacteria deposited on mucosal surfaces and prevent acute invasive infections. In many chronic infections, however, bacteria live in biofilms, which are distinct, matrix-encased communities specialized for surface persistence. The transition from a free-living, independent existence to a biofilm lifestyle can be devastating, because biofilms notoriously resist killing by host defence mechanisms and antibiotics. We hypothesized that the innate immune system possesses specific activity to protect against biofilm infections. Here we show that lactoferrin, a ubiquitous and abundant constituent of human external secretions, blocks biofilm development by the opportunistic pathogen Pseudomonas aeruginosa. This occurs at lactoferrin concentrations below those that kill or prevent growth. By chelating iron, lactoferrin stimulates twitching, a specialized form of surface motility, causing the bacteria to wander across the surface instead of forming cell clusters and biofilms. These findings reveal a specific anti-biofilm defence mechanism acting at a critical juncture in biofilm development, the time bacteria stop roaming as individuals and aggregate into durable communities.     

口腔细菌表面糖苷酶的生物学功能研究

口腔细菌是引起龋齿的关键因素。口腔细菌和黏附在牙齿表面的唾液大分子相互作用,在牙齿表面形成早期牙菌斑生物膜,随后更多的细菌加入到生物膜中生长并最终导致龋齿和牙周炎等疾病。唾液为细菌的黏附提供配体,为细菌的生长提供碳源和氮源,但是细菌如何利用以及利用哪些唾液大分子进行生长还不清楚。许多口腔细菌细胞表面和细胞内有不同的糖苷酶水解糖链。本综述总结了笔者对口腔细菌的研究,揭示不同细菌利用人的唾液生长的能力不同,有的生长良好,有的甚至不能单独在唾液中生长;而口腔共生菌Streptococcus gordonii DL1在唾液中生长良好是依赖于细菌表面的3个糖苷酶,它们捕食唾液中富含脯氨酸的糖蛋白的N-糖链,是该细菌在唾液中生长关键的第一步;而且不同的糖苷酶对底物有严格的特异性,糖链只能被依次水解。不同细菌表面有不同的糖苷酶,能够合作水解糖链从而在唾液中相互喂养并在牙齿表面共生,是笔者下一步的研究方向。     

猪胸膜放线杆菌中黏附素的研究进展

胸膜肺炎放线杆菌(Actinobacillus pleuropneumoniae,APP)是引起猪传染性胸膜肺炎疾病的病原菌,APP引起猪致病的毒力因子有多种,其中黏附素作为细菌粘附宿主的第一步中的关键作用被广泛关注.黏附是APP感染宿主的第一步,分泌到革兰氏阴性菌表面的自转运黏附索调节着细菌对宿主细胞的黏附,是重要的...     

Natural conjugative plasmids induce bacterial biofilm development

Horizontal gene transfer is a principal source of evolution leading to change in the ecological character of bacterial species. Bacterial conjugation, which promotes the horizontal transfer of genetic material between donor and recipient cells by physical contact, is a phenomenon of fundamental evolutionary consequence. Although conjugation has been studied primarily in liquid, most natural bacterial populations are found associated with environmental surfaces in complex multispecies communities called biofilms. Biofilms are ideally suited to the exchange of genetic material of various origins, and it has been shown that bacterial conjugation occurs within biofilms. Here I investigate the direct contribution of conjugative plasmids themselves to the capacity of the bacterial host to form a biofilm. Natural conjugative plasmids expressed factors that induced planktonic bacteria to form or enter biofilm communities, which favour the infectious transfer of the plasmid. This general connection between conjugation and biofilms suggests that medically relevant plasmid-bearing strains are more likely to form a biofilm. This may influence both the chances of biofilm-related infection risks and of conjugational spread of virulence factors.     

没食子鞣质及其有效提取物对牙菌斑生物膜形态结构和活性的作用

研究药物没食子鞣质及其有效提取物对牙菌斑生物膜形态结构和活力的影响,了解常态生物膜形成过程中生物膜活力的变化,以及药物作用下生物膜形态结构和活力的变化,探讨药物对牙菌斑生物膜的作用机制.采用倒置荧光显微镜结合特异荧光染料标记常态牙菌斑生物膜生长过程中死菌和活菌变化,及药物处理后牙菌斑生物膜中死菌和活菌的构成,观察常态牙菌斑生物膜形竺过程中生物膜结构及活力的变化以及药物作用下生物膜形态结构和活力的变化;研究和评估常态牙菌斑生物膜的形态结构和细菌活力及实验药物对牙菌斑生物膜结构和细菌活性的影响.结果显示,从早期细菌定植粘附到形成成熟生物膜结构的各个过程中都存在一定数量的死菌.24 h常态生物膜结构中活菌面积占主导地位,有少量的死菌存在,细菌互相紧密粘附在一起,生物膜结构清晰,其间有各管道结构.0.05%洗必泰24 h细菌生物膜作用后,细菌总量明显下降,残存滞留的细菌基本为死菌.0.023%的氟化钠(NaF)作用细菌生物膜后,生物膜结构发生了明显的变化,细菌总量明显减少,但是存在的细菌以活菌为主.经过4mg/mL的没食子鞣质及其有效提取物作用后,生物膜中各管道结构模糊不清,细菌变得散开,生物膜细菌总量减少,与24 h常态生物膜比,有显著差异(P<0.05),生物膜结构密度下降,其中有大量的死菌和部分活菌存在.实验组活菌百分比与阴性对照组活菌百分比相比有显著差异(P<0.05).由此得出结论,实验药物对牙菌斑生物膜的作用一方面是对生物膜中细菌的杀灭,另一方面是改变牙菌斑孝竺膜的形态结构,降低生物膜密度及调整生物膜内部死活菌的比例.     

In vitro antibacterial and osteogenic properties of plasma sprayed silver-containing hydroxyapatite coating

The objective of the present investigation was to characterize the antibacterial and osteogenic properties of plasma sprayed silver-containing hydroxyapatite （HA/Ag） coating in vitro. HA/Ag coating was deposited via vacuum plasma spraying. The concentration of silver ions released from HA/Ag coating, the efficacy of the HA/Ag coating against bacterial biofilm development, the effect of the HA/Ag coating on early adhesion and ossification of osteoblast cells in vitro was measured. The silver ion concentration released from the HA/Ag coating was between the minimum inhibitory concentration to bacteria and the cytotoxic concentration. Bacterial biofilm inhibition studies indicated an antibacterial activity on the HA/Ag coating surface when compared with hydroxyapatite （HA） coating alone. Moreover, it was demonstrated that osteoblast cell adhesion and mineralization occurred on the HA/Ag coating surface during the testing period. We conclude that the vacuum plasma sprayed HA/Ag coating possesses good antibacterial capability and osteogenic properties in vitro and represents a promising candidate for coating orthopedic implants.     

光照波长影响光合细菌生物膜生长特性实验

在平板式生物膜反应器内,研究波长范围为420~590 nm的3种不同单色光源对高效光合产氢细菌生物膜生长特性的影响进行实验,讨论了不同光照波长对沼泽红假单胞菌生物膜表面覆盖率、膜厚、干重和密度的影响。实验结果表明,不同的光照波长对生物膜生长速率及结构具有重要影响,在相同的时间间隔内,生物膜表面覆盖率随着光照波长的增加而增加,而光照波长对生物膜干重影响很小,在实验运行4 d后,生物膜厚度随着波长的增加而减小;光照波长越长,生物膜密度越高,这是由于较短的光照波长抑制了细菌的分裂及胞外高聚物的生成。     

黄芩提取物对脓肿分枝杆菌生长及生物膜形成的影响

为了研究黄芩提取物对脓肿分枝杆菌浮游细菌及生物膜的影响，本研究以脓肿分枝杆菌标准菌株ATCC 19977以及临床分离株作为受试菌，采用Alarmar-Blue液体药敏法测定黄芩提取物对脓肿分枝杆菌的最小抑菌浓度（MIC），平板涂布法测定最小杀菌浓度（MBC），结晶紫染色法和扫描电子显微镜分析黄芩提取物对脓肿分枝杆菌生物膜形成量及形态结构的影响，进一步采用了RT-qPCR探究黄芩提取物对分枝菌酸合成相关基因表达的影响.结果表明黄芩提取物对脓肿分枝杆菌标准菌株ATCC 19977以及8株临床分离株的MIC90为50~100 mg/mL，MBC为50~200 mg/mL；黄芩提取物可显著降低脓肿分枝杆菌生物膜形成量（P<0.05），破坏生物膜的结构，并且显著降低分枝菌酸合成相关基因表达量（P<0.01）.本研究表明黄芩提取物能够抑制脓肿分枝杆菌的生长以及生物膜的形成.     

A taxa-area relationship for bacteria

A positive power-law relationship between the number of species in an area and the size of that area has been observed repeatedly in plant and animal communities. This species-area relationship, thought to be one of the few laws in ecology, is fundamental to our understanding of the distribution of global biodiversity. However, such a relationship has not been reported for bacteria, and little is known regarding the spatial distribution of bacteria, relative to what is known of plants and animals. Here we describe a taxa-area relationship for bacteria over a scale of centimetres to hundreds of metres in salt marsh sediments. We found that bacterial communities located close together were more similar in composition than communities located farther apart, and we used the decay of community similarity with distance to show that bacteria can exhibit a taxa-area relationship. This relationship was driven primarily by environmental heterogeneity rather than geographic distance or plant composition.     

微量量热法对细菌最低生长温度的研究

用微量量热计测定了大肠杆菌,金黄色葡萄球菌,白色葡萄球菌和枯草杆菌,在牛肉膏汤液体中不同温度下的产热曲线,按限制性条件下微生物生长模型进行了处理,求得了细菌的生长速率常数k,衰减速度常数β和在实验条件下细菌增长的最大倍数M和细菌的最大数目K,建立了细菌生长速率常数k和细菌生长温度T的定量关系,得到k=0时的温度T0,即细菌的最低生长温度。     

Shewanella algae对纯锌腐蚀性能的影响

【目的】在室内模拟条件下研究海藻希瓦氏菌(Shewanella algae)对纯锌牺牲阳极腐蚀的影响。【方法】利用微生物分析、交流阻抗测试技术、扫描电镜及荧光显微等方法,测试Shewanella algae的生长曲线、开路电位、电化学阻抗、表面形貌等。【结果】在含细菌体系中,细菌通过代谢活动消耗掉溶解氧,在试样表面形成一层生物膜。该生物膜阻挡了腐蚀介质与试样表面的接触,从而使试样的腐蚀受到抑制。荧光显微镜观察结果表明,浸泡7d,试样表面形成完整的生物膜,但随着营养物质及氧气的消耗,生物膜逐渐脱落。【结论】该细菌可以使纯锌试样的腐蚀电位升高,并且显著抑制试样的腐蚀。该细菌生物膜的形成需要一定的时间及充足的营养物质和氧气。     

生物膜和生物膜形成菌的研究

细菌生物膜是一个复杂的微生物群落,生物膜巾除了水和细菌以外,还含有细菌分泌的胞外聚合物、吸附的营养物质、代谢产物及DNA等细菌裂解产物.介绍细菌生物膜的形成过程,并综述了近年来医学领域以几种成膜力强的条件致病菌为研究对象,从基因水平上证实了细菌细胞表面结构鞭毛、纤毛、胞外聚合物和群体感应信号分子等细胞因子对生物膜形成的影响.     

Structural identification of a bacterial quorum-sensing signal containing boron

Cell-cell communication in bacteria is accomplished through the exchange of extracellular signalling molecules called autoinducers. This process, termed quorum sensing, allows bacterial populations to coordinate gene expression. Community cooperation probably enhances the effectiveness of processes such as bioluminescence, virulence factor expression, antibiotic production and biofilm development. Unlike other autoinducers, which are specific to a particular species of bacteria, a recently discovered autoinducer (AI-2) is produced by a large number of bacterial species. AI-2 has been proposed to serve as a 'universal' signal for inter-species communication. The chemical identity of AI-2 has, however, proved elusive. Here we present the crystal structure of an AI-2 sensor protein, LuxP, in a complex with autoinducer. The bound ligand is a furanosyl borate diester that bears no resemblance to previously characterized autoinducers. Our findings suggest that addition of naturally occurring borate to an AI-2 precursor generates active AI-2. Furthermore, they indicate a potential biological role for boron, an element required by a number of organisms but for unknown reasons.     

An independent microbial flora of the epithelium and its role in the ecomicrobiology of the rumen

IT has been suggested that the bacterial flora of the rumen should be considered as three distinct, interacting populations-the bacteria of rumen fluid (the population which has been studied most extensively), the bacteria associated with food particles, and the bacteria adhering to the epithelial wall of the organ(1). Until now, studies of the 'epithelial' population have been restricted to examination of postmortem samples of wall tissue and its attached bacterial flora(2-5). A recently developed technique(6) for feeding young sheep for long periods solely by infusion of protein and other essential nutrients into the abomasum, and of volatile fatty acids and bicarbonate buffer into the rumen, has provided us with an opportunity to study in isolation the role of the bacterial population of the wall in the ecomicrobiology of the rumen in the living animal. Our studies show that this population can exist independently of the other two populations, that it is primarily responsible for urea digestion in the rumen and that it initiates breakdown of dead epithelial tissue. Furthermore, our results point to an inverse relationship between ammonia concentration and ureolytic activity in rumen fluid, which may account for the control which ammonia exerts over flux of urea across the rumen wall(7-9).     

中国创业投资行业的波动特征研究

中国创业投资行业的发展呈现出高度的波动性,而这种波动性会对技术创新等经济活动产生较大的负面影响。采用计量经济学的相关方法对中国创业投资行业的波动特征进行研究,结果发现,中国创业投资行业的波动是一种增长波动,即创业投资行业具有确定性的增长趋势,其发展过程是围绕确定性增长趋势上下波动的过程。研究同时发现,1994年以来中国创业投资行业的发展经历了3个较为完整的波动周期,周期内波动情况相当剧烈。