鲍曼不动杆菌菌毛在细菌生物膜形成中的作用

目的通过观察鲍曼不动杆菌菌毛,了解菌毛结构在生物被膜形成过程中的作用。方法以ICU的医院感染患者的腹腔手术后引流液、痰及呼吸机导管内壁附着物等为材料分离鉴定细菌,制备细菌的电镜标本,通过超微结构观察鲍曼不动杆菌菌体表面的菌毛与生物被膜形成的相关性。结果新分离的鲍曼不动杆菌菌体表面存在菌毛,菌毛与生物膜形成过程中的粘附有关。结论菌毛粘附是生物被膜形成的原因之一。     

噬菌体及其裂解酶对细菌生物被膜作用的研究进展

细菌形成的生物被膜,可保护细菌不易被抗生素杀死,这给临床上相应疾病的治疗及医疗器械的消毒带来极大困难。研究表明,噬菌体及其裂解酶对生物被膜有降解作用。噬菌体能清除细菌在有生物活性或无生物活性的介质表面形成的生物被膜。此外,噬菌体裂解酶比如LySMP、肽酶CHAPk、细胞壁溶解酶CWHs等能清除特定的生物被膜,这可能与裂解酶直接溶菌和裂解细菌细胞外基质有关。同时,与抗生素、钴离子、氯等物质联合使用时,噬菌体对生物被膜的清除作用会更强。本文从噬菌体、噬菌体编码的裂解酶、以及它们联合其他物质对细菌生物被膜的作用进行综述,并对其实际应用做了展望。     

细菌显微追踪技术在生物被膜中的应用

细菌生物被膜是粘附于物体表面的由细菌细胞及其胞外物质组成的复杂膜样物聚集体,具有很强的耐药性和免疫逃逸能力。生物被膜内细菌的代谢活性、运动状态等与浮游细菌有明显区别。近年来,先进的显微成像技术结合新型图像处理方法,在研究细菌的运动、生理等方面发挥了重要作用。本文围绕生物被膜,概述了细菌显微追踪技术在其研究中的应用。主要从细菌的运动方式和生物被膜形成过程的调控两方面出发,介绍了在单细胞水平上利用该技术研究生物被膜的进展,包括细菌的游泳、蹭行、群集运动和多种信号通路调控下生物被膜的形成过程等,并展望了该技术在生物被膜其他相关研究领域的应用前景。     

c-di-AMP调控细菌生物被膜的形成

细菌生物被膜是细菌持续性致病的重要机制。研究细菌生物被膜的形成和发展可为顽固性细菌感染防治提供新的思路与策略。环二腺苷酸c-di-AMP(Cyclic diadenosine monophosphate)是继c-di-GMP之后在细菌中新发现的一种核苷酸第二信使分子。研究发现,c-di-AMP参与调节细菌多种生理功能,包括细菌生长代谢、生物被膜形成、细胞壁的合成以及细菌毒力因子等。本文综述了c-di-AMP参与调控细菌生物被膜形成的不同方式及其分子机制。鉴于c-di-AMP在调控细菌生物被膜中的重要性,其可作为抗细菌生物被膜感染新药研发的潜在靶点。     

铜绿假单胞菌蹭行运动单细胞分析方法的建立及应用

蹭行运动在生物被膜形成过程中对细菌适应表面环境以及后续生物被膜三维结构的形成起重要作用。因此,对蹭行运动的原位表征、量化是生物被膜研究中的重要科学问题之一。我们通过高通量数据采集、自动化图像处理、数据库建立以及图形化输出等技术手段,建立了一整套基于单细菌的统计分析方法。利用这一方法对蹭行运动中的行走、弹射过程进行了详细分析,发现弹射运动过程中存在以0.9 s为周期的周期性弛豫。并定量比较了群体感知信号分子对蹭行运动的影响,发现加入信号分子后蹭行运动在高速区明显增强。该方法的建立为后续蹭行运动分子机制以及调节方式的研究奠定了基础。     

铜绿假单胞菌生物被膜组成及其受群体感应系统和c-di-GMP调控的研究进展

作为人类条件性感染的前三大病原菌之一的铜绿假单胞菌,是一种革兰氏阴性细菌,对免疫功能低下和囊性纤维化患者可以造成严重和持续性感染。造成这种持续感染的原因主要是由于细菌接收外界信号后,在自身调控网络的协同作用下,会依附于固体表面,并产生胞外多糖、基质蛋白和胞外DNA等大分子物质形成高度结构化的膜状复合物将自身包裹形成生物被膜群体结构。生物被膜可以有效帮助细菌定殖、提高细菌对抗菌物质和宿主免疫反应的抵抗能力、促进群落细菌的细胞-细胞之间的信号交流等,是临床治疗中病原菌慢性感染和反复感染最重要的原因之一。本篇综述重点介绍了铜绿假单胞菌生物被膜的各组成成分及其在生物被膜形成中的重要功能,并进一步阐述了群体感应系统(las、rhl、pqs与iqs)和c-di-GMP对铜绿假单胞菌生物被膜形成的调控作用。通过本篇综述可以更清晰地了解细菌生物被膜形成和调控的过程,为开发新的治疗生物被膜感染策略提供帮助。     

黄色粘球菌基于复杂社会性细胞行为的生物被膜

黄色粘球菌具有多样化的细胞行为,具备典型多细胞水平的社会性特征。其形成的生物被膜是目前认知的最为复杂的单种群细菌生物被膜之一。黄色粘球菌的社会性细胞行为主导了其生物被膜形成过程中的关键环节,包括固体介质表面的细胞运动、群体细胞的捕食、亲缘细胞的识别、子实体的发育、粘孢子的分化以及细胞程序性死亡等行为过程。文中将介绍相关领域的研究进展。     

葡萄糖类似物甲基葡萄糖对表皮葡萄球菌生物被膜形成的影响及调节机制的研究

生物被膜(Biofilm)是条件致病菌表皮葡萄球菌(Staphylococcusepidermidis)的主要致病因素,生物被膜的形成依赖多糖PIA的合成,PIA合成与细菌糖代谢相关。通过研究葡萄糖类似物甲基葡萄糖(MethylDglucoside,MG)对生物被膜的形成及相关基因表达的影响,考察生物被膜形成的调控机制并寻找抑制生物被膜形成的方法。甲基葡萄糖能抑制97337株生物被膜的形成,而且不同浓度的甲基葡萄糖对生物膜作用不同。甲基葡萄糖对97337株生物被膜形成的早期的粘附有较强的抑制作用;不同浓度的甲基葡萄糖处理后对ica和AtlE基因的mRNA表达水平影响不大,但能诱导agr基因的表达,这与甲基葡萄糖处理不同时间后的结果一致;而且甲基葡萄糖处理后97337的表面相关蛋白的组成明显改变。甲基葡萄糖对生物膜的抑制并不直接由于它对生长的抑制,它对细菌生长和生物被膜形成的抑制与其在细菌糖代谢中的竞争性相关;甲基葡萄糖能通过调控agr基因的表达改变细菌表面从而抑制97337的早期粘附和生物被膜的形成,但没有通过调控icaADBC、icaR的表达抑制生物膜的形成,可能与其对合成PIA相关糖基转移酶的竞争性抑制相关。     

细菌生物被膜检测方法的研究进展

细菌生物被膜(bacterial biofilm,BF)是细菌黏附于接触物表面,由细菌自身分泌的胞外基质包裹形成的多细胞微生物群体,是微生物界细菌普遍的生存状态。基于生物被膜的物理屏障作用和膜内特殊微环境,其具有多重耐药性以及较强的黏附性、抗吞噬性等特性,导致所致疾病迁延不愈,已成为医疗卫生领域的重大挑战。早期、快速、准确检测生物被膜形成对及时有效防治其感染性疾病至关重要。现从表型和基因型检测两个方面对细菌生物被膜检测方法作一综述。     

生物被膜在病原细菌与植物识别中的作用

生物被膜是微生物附着在生物或非生物表面所形成的一种三维结构,细胞被其自身所产生的胞外聚合物所包围,生物被膜的形成被认为是微生物应对生物和非生物胁迫时所产生的一种自我防御机制。众多微生物能够在植物叶、维管束和根等组织中生长,并在植物不同组织表面附着形成生物被膜,病原细菌的生物被膜随植物内部环境动态变化是其有效发挥致病作用的关键,研究植物病原细菌生物被膜调控机制是认识植物-病原菌互作的重要方面。文中将系统地介绍植物病原细菌生物被膜特征、组成成分、分子调控机制及最新研究进展。     

Susceptibility of Staphylococcus aureus biofilms to reactive discharge gases

Formation of bacterial biofilms at solid-liquid interfaces creates numerous problems in both industrial and biomedical sciences. In this study, the susceptibility of Staphylococcus aureus biofilms to discharge gas generated from plasma was tested. It was found that despite distinct chemical/physical properties, discharge gases from oxygen, nitrogen, and argon demonstrated very potent and almost the same anti-biofilm activity. The bacterial cells in S. aureus biofilms were killed (>99.9%) by discharge gas within minutes of exposure. Under optimal experimental conditions, no bacteria and biofilm re-growth from discharge gas treated biofilms was found. Further studies revealed that the anti-biofilm activity of the discharge gas occurred by two distinct mechanisms: (1) killing bacteria in biofilms by causing severe cell membrane damage, and (2) damaging the extracellular polymeric matrix in the architecture of the biofilm to release biofilm from the surface of the solid substratum. Information gathered from this study provides an insight into the anti-biofilm mechanisms of plasma and confirms the applications of discharge gas in the treatment of biofilms and biofilm related bacterial infections.     

Comparison of the Phenotypes and Genotypes of Biofilm and Solitary Epiphytic Bacterial Populations on Broad-Leaved Endive

The discovery that biofilms are ubiquitous among the epiphytic microflora of leaves has prompted research about the impact of biofilms on the ecology of epiphytic microorganisms and on the efficiency of strategies to manage these populations for disease control and to ensure food safety. Biofilms are likely to influence the microenvironment and phenotype of the microorganisms they harbor. However, it is also important to determine whether there are differences in the types of bacteria within biofilms compared to those outside of biofilms so as to better target microorganisms via disease control strategies. Broad-leaved endive (Cichorium endivia var. latifolia) harbors biofilms containing fluorescent pseudomonads. These bacteria can cause considerable post-harvest losses when this plant is used for manufacturing minimally processed salads. To determine whether the population structure of the fluorescent pseudomonads in biofilms is different from that outside of biofilms on the same leaves, bacteria were isolated quantitatively from the biofilm and solitary components of the epiphytic population on leaves of field-grown broad-leaved endive. Population structure was determined in terms of taxonomic identities of the bacteria isolated, in terms of genotypic profiles, and in terms of phenotypic traits related to surface colonization and biofilm formation. The results illustrate that there are no systematic differences in the composition and structure of biofilm and solitary populations of fluorescent pseudomonads, in terms of either genotypic profiles or phenotypic profiles of the strains. However, Gram-positive bacteria tended to occur more frequently within biofilms than outside of biofilms. We suggest that leaf colonization by fluorescent pseudomonads involves a flux of cells between biofilm and solitary states. This would allow bacteria to exploit the advantages of these two types of existence; biofilms would favor resistance to stressful conditions, whereas solitary cells could foster spread of bacteria to newly colonizable sites on leaves as environmental conditions fluctuate.     

Amyloid-containing biofilms and autoimmunity

Bacteria are microscopic, single-celled organisms known for their ability to adapt to their environment. In response to stressful environmental conditions or in the presence of a contact surface, they commonly form multicellular aggregates called biofilms. Biofilms form on various abiotic or biotic surfaces through a dynamic stepwise process involving adhesion, growth, and extracellular matrix production. Biofilms develop on tissues as well as on implanted devices during infections, providing the bacteria with a mechanism for survival under harsh conditions including targeting by the immune system and antimicrobial therapy. Like pathogenic bacteria, members of the human microbiota can form biofilms. Biofilms formed by enteric bacteria contribute to several human diseases including autoimmune diseases and cancer. However, until recently the interactions of immune cells with biofilms had been mostly uncharacterized. Here, we will discuss how components of the enteric biofilm produced in vivo, specifically amyloid curli and extracellular DNA, could be interacting with the host's immune system causing an unpredicted immune response.     

Synthetic biology in biofilms: Tools,challenges, and opportunities

The field of synthetic biology seeks to program living cells to perform novel functions with applications ranging from environmental biosensing to smart cell-based therapeutics. Bacteria are an especially attractive chassis organism due to their rapid growth, ease of genetic manipulation, and ability to persist across many environmental niches. Despite significant progress in bacterial synthetic biology, programming bacteria to perform novel functions outside the well-controlled laboratory context remains challenging. In contrast to planktonic laboratory growth, bacteria in nature predominately reside in the context of densely packed communities known as biofilms. While biofilms have historically been considered environmental and biomedical hazards, their physiology and emergent behaviors could be leveraged for synthetic biology to engineer more capable and robust bacteria. Specifically, bacteria within biofilms participate in complex emergent behaviors such as collective organization, cell-to-cell signaling, and division of labor. Understanding and utilizing these properties can enable the effective deployment of engineered bacteria into natural target environments. Toward this goal, this review summarizes the current state of synthetic biology in biofilms by highlighting new molecular tools and remaining biological challenges. Looking to future opportunities, advancing synthetic biology in biofilms will enable the next generation of smart cell-based technologies for use in medicine, biomanufacturing, and environmental remediation.     

Bacterial biofilms as a natural form of existence of bacteria in the environment and host organism

Advances in microscopic analysis and molecular genetics research methods promoted the acquisition of evidence that natural bacteria populations exist predominately as substrate attached biofilms. Bacteria in biofilms are able to exchange signals and display coordinated activity that is inherent to multicellular organisms. Formation of biofilm communities turned out to be one of the main survival strategies of bacteria in their ecological niche. Bacteria in attached condition in biofilm are protected from the environmental damaging factors and effects of antibacterial substances in the environment and host organism during infection. According to contemporary conception, biofilm is a continuous layer of bacterial cells that are attached to a surface and each other, and contained in a biopolymer matrix. Such bacterial communities may be composed of bacteria of one or several species, and composed of actively functioning cells as well as latent and uncultured forms. Particular attention has recently been paid to the role of biofilms in the environment and host organism. Microorganisms form biofilm on any biotic and abiotic surfaces which creates serious problems in medicine and various areas of economic activity. Currently, it is established that biofilms are one of the pathogenetic factors of chronic inflection process formation. The review presents data on ubiquity of bacteria existence as biofilms, contemporary methods of microbial community analysis, structural-functional features of bacterial biofilms. Particular attention is paid to the role of biofilm in chronic infection process formation, heightened resistance to antibiotics of bacteria in biofilms and possible mechanisms of resistance. Screening approaches for agents against biofilms in chronic infections are discussed.     

Membrane Vesicle Formation as a Multiple-Stress Response Mechanism Enhances Pseudomonas putida DOT-T1E Cell Surface Hydrophobicity and Biofilm Formation

Among the adaptive responses of bacteria to rapid changes in environmental conditions, those of the cell envelope are known to be the most crucial. Therefore, several mechanisms with which bacteria change their cell surface and membranes in the presence of different environmental stresses have been elucidated. Among these mechanisms, the release of outer membrane vesicles (MV) in Gram-negative bacteria has attracted particular research interest because of its involvement in pathogenic processes, such as that of Pseudomonas aeruginosa biofilm formation in cystic fibrosis lungs. In this study, we investigated the role of MV formation as an adaptive response of Pseudomonas putida DOT-T1E to several environmental stress factors and correlated it to the formation of biofilms. In the presence of toxic concentrations of long-chain alcohols, under osmotic stress caused by NaCl, in the presence of EDTA, and after heat shock, cells of this strain released MV within 10 min in the presence of a stressor. The MV formed showed similar size and charge properties, as well as comparable compositions of proteins and fatty acids. MV release caused a significant increase in cell surface hydrophobicity, and an enhanced tendency to form biofilms was demonstrated in this study. Therefore, the release of MV as a stress response could be put in a physiological context.     

Antimicrobial activity of surface attached marine bacteria in biofilms

Relatively little is known about the microbial ecology of biofilm communities or the diversity of antimicrobial molecules that they produce to regulate these communities. This study tested whether the production of antimicrobial activity in biofilm cultures is enhanced towards competing bacteria found in those biofilms. First, the production of antimicrobial activity of marine bacteria grown in biofilms was tested. Fourteen of the 105 marine isolates tested were found to produce antimicrobial factors when grown in biofilms. The antimicrobial activity produced by these isolates in biofilms was more potent and inhibited a broader range of target bacteria grown in biofilms compared to shaken liquid cultures. In a separate experiment, we found that cultivation in biofilms containing produced metabolites from an ‘inducer’ bacterium stimulated the production of antimicrobial molecules by ‘producer’ bacteria that were active against the ‘inducer’ bacterium. Overall, the study suggests that surface attached marine bacteria can target their antimicrobial activity towards competing bacteria in biofilms.     

人工纳米材料与生物膜相互作用机制及影响因素研究进展

人工纳米材料在水体中的环境行为与生物环境安全问题成为环境科学领域研究的热点,人工纳米材料与生物膜相互作用机制和影响因素是其中迫切需要研究解决的关键科学问题。本文主要探讨了人工纳米材料释放进入到水体中后对生物膜细菌活性、微生物群落结构、净污活性等的毒性效应,分析了人工纳米材料对生物膜的毒性作用机制及其影响因素,同时探讨了生物膜对人工纳米材料的吸附作用及机理,为深入研究人工纳米材料与生物膜的相互作用机制提供了重要的理论基础。     

Biofilm formation in plant-microbe associations

Bacteria adhere to environmental surfaces in multicellular assemblies described as biofilms. Plant-associated bacteria interact with host tissue surfaces during pathogenesis and symbiosis, and in commensal relationships. Observations of bacteria associated with plants increasingly reveal biofilm-type structures that vary from small clusters of cells to extensive biofilms. The surface properties of the plant tissue, nutrient and water availability, and the proclivities of the colonizing bacteria strongly influence the resulting biofilm structure. Recent studies highlight the importance of these structures in initiating and maintaining contact with the host by examining the extent to which biofilm formation is an intrinsic component of plant-microbe interactions.