土壤矿物与微生物相互作用的机理及其环境效应

土壤矿物与微生物相互作用是地球表层系统中重要的生态过程.微生物或生物分子与矿物间的吸附(粘附)是两者相互作用的基础.吸附(粘附)是一个由分子间力、静电力、疏水作用力、氢键和空间位阻效应等多种作用力或作用因素共同决定、影响的物理化学过程.因此,微生物和矿物的表面性质如表面电荷、疏水性和它们所处的环境条件如pH、电解质浓度、温度等,都影响着矿物-微生物吸附(粘附)过程.微生物细胞或酶可吸附于矿物表面,其结果是细胞代谢或酶活性会发生明显变化,并进一步影响土壤中诸多相关的生态、环境过程.结合4种典型的初始吸附理论:表面自由能热力学理论、DLVO理论、吸附等温线理论和表面复合物理论及本课题组近年来的研究成果,对土壤矿物与微生物相互作用的类型、机理、作用力和现代研究技术等方面的最新研究进展进行了较为全面的论述,对土壤矿物-微生物相互作用的环境效应进行了讨论,并就该领域今后研究工作的特点及应关注的问题进行了展望.     

The antistaphylococcal activity of thionium in in vitro experiments

The paper deals with the experimental study of antistaphylococcal properties of thionium--a derivative of bis-quarternary ammonium compounds. High bactericide activity of the preparation is revealed as a result; it is preserved under high contents of protein substances in the media. The sensitivity of staphylococcal strains to thionium is not affected by the initial sensitivity of microorganisms to antibiotics. The preparations interaction with benzylpenicillin and gentamycin has been studied. Synergist effect of sub-bacteriostatic doses of thionium with the mentioned antibiotics has been found. Effect of benzylpenicillin increases 4-32 times, that of gentamycin--64-512 times independent of the primary sensitivity to these antibiotics. The further study of a new antistaphylococcal preparation is advisable.     

Influence of antibiotics (benzylpenicillin,pharmazin, and nystatin) on the number of microorganisms in ordinary chernozem

In model experiments, the influence of pharmaceutical antibiotics (benzylpenicillin, pharmazin, and nystatin) in different doses (100, 300, 450, and 600 mg/kg) on a number of microorganisms of the chernozem region has been studied. All the studied doses of antibiotics had reliable and overwhelming impacts on the amount of soil microorganisms. The time between a dose of antibiotics and a change in the number of microorganisms in the soil is shown to have a linear dependence. The studied groups of soil microorganisms in relation to pharmaceutical antibiotics showed a hierarchy of resistance (high concentration): Azotobacter > amylolytic bacteria > ammonifying bacteria > micromycetes.     

Lateral and Perpendicular Interaction Forces Involved in Mobile and Immobile Adhesion of Microorganisms on Model Solid Surfaces

Gliding and near-surface swimming of microorganisms are described as a mobile form of microbial adhesion that need not necessarily be reversible. It is argued that the reversibility of microbial adhesion depends on the depth of the secondary interaction minimum, calculated from the forces between an organism and a substratum acting in a direction perpendicular to the substratum surface. The mobility of adhering microorganisms depends on lateral interactions between the organisms. On ideally homogeneous and smooth model surfaces, only mobile adhesion occurs because the multibody, lateral interactions are weak compared with the thermal or Brownian motion energy of the organisms. Minor chemical or structural heterogeneities, which exist on all real-life surfaces, yield a lateral interaction on adhering microorganisms. This causes their immobilization, which helps to explain the physicochemical nature of microbial gliding or near-surface swimming. Moreover, these lateral interaction energies are one order of magnitude smaller than the Lifshitz-Van der Waals, electrostatic, and acid-base forces acting perpendicular to substratum surfaces that are responsible for adhesion. Received: 2 April 1998 / Accepted: 26 May 1998     

Emergence of antibiotic-resistant extremophiles (AREs)

Excessive use of antibiotics in recent years has produced bacteria that are resistant to a wide array of antibiotics. Several genetic and non-genetic elements allow microorganisms to adapt and thrive under harsh environmental conditions such as lethal doses of antibiotics. We attempt to classify these microorganisms as antibiotic-resistant extremophiles (AREs). AREs develop strategies to gain greater resistance to antibiotics via accumulation of multiple genes or plasmids that harbor genes for multiple drug resistance (MDR). In addition to their altered expression of multiple genes, AREs also survive by producing enzymes such as penicillinase that inactivate antibiotics. It is of interest to identify the underlying molecular mechanisms by which the AREs are able to survive in the presence of wide arrays of high-dosage antibiotics. Technologically, "omics"-based approaches such as genomics have revealed a wide array of genes differentially expressed in AREs. Proteomics studies with 2DE, MALDI-TOF, and MS/MS have identified specific proteins, enzymes, and pumps that function in the adaptation mechanisms of AREs. This article discusses the molecular mechanisms by which microorganisms develop into AREs and how "omics" approaches can identify the genetic elements of these adaptation mechanisms. These objectives will assist the development of strategies and potential therapeutics to treat outbreaks of pathogenic microorganisms in the future.     

Nanomechanical changes in probiotic bacteria under antibiotics exposure: Implications on Lactobacillus biofilm formation

Recognition of the microbial cell's surface constituents' biophysical properties is an important research topic, allowing a better understanding of the cell's behaviour under different conditions. Atomic force microscopy (AFM) was employed in this study to analyse the basis of the nanomechanical changes in probiotic bacteria under nitrofurantoin, furazolidone, and nitrofurazone exposure. Recorded significant changes in the two Lactobacillus strains cells morphology, topography, and adhesion parameters resulted in the increase of the cells' longitude (up to 2.58 μm), profile height (by around 0.50 μm), and decrease in the adhesion force (up to 13.58 nN). Young's modulus and adhesion energy decreased within 96 h, however with no negative effect on the cells' morphology or loss of structural integrity. Observed modifications present the mode of action of the 5-nitrofuran derivative antibiotics on probiotic biofilm formation and suggest activation of the multilevel adaptation mechanisms to counteract unfavorable environments. A visual change in bacterial morphology such as an increased surface-to-volume ratio might be a link between molecular-level events and outcomes in individual cells and biofilms. This paper for the first time shows, that these antibiotics affect the properties of non-target microorganisms as lactobacilli, and might impair biofilm formation. However, the degree of such transformations depends on the delivered active substance.     

Products containing biocides: perceptions and realities

The mechanisms of action for chemical germicides and antibiotics for inactivating microorganisms are significantly different and methods for determining resistance by microorganisms to these agents are also different. Chemical germicides usually have multiple targets and the mechanisms for inactivation and resistance are not measured in absolute terms but rather in the rapidity with which they reduce levels of microorganisms. The term tolerance is much more suited for germicides than the term resistance. The mechanism of resistance to chemical germicides is often dependent on the concentration of the germicide. At high concentrations multiple cellular and metabolic targets are involved, and at low concentrations fewer cellular targets. In contrast antibiotics usually have a singular cellular or metabolic target and resistance implies the ability of the microorganism to grow in the presence of the antibiotic, and in a clinical sense, to initiate or continue infection in the presence of the antibiotic. When methods used to assess resistance to antibiotics are applied to chemical germicides, inappropriate interpretations can be made regarding the ability of microorganisms to develop resistance to antibiotics as a result of developing resistance to chemical germicides. The use of chemical germicides in health-care institutions and especially the home setting has increased in recent years. Although there may be an overuse of germicides in these settings the consequence is a cost issue and not one that involves the development of antibiotic resistant microorganisms.     

Proteus adhesion to intestinal epithelium

The adhesive properties of Proteus strains isolated from different sources have been studied under conditions similar to the real interaction of microorganisms with the epithelial cells of intestine. A comparison of the adhesive properties of Proteus and of colon Bacillus has shown that the value of the strong adhesion to the mucosa of Proteus isolated under enterocolitis at the same bulk concentrations of the infectious suspension is 2-3 order less than that of E. coli. The adhesion of Proteus to the surface of epithelial cells begins at bulk concentrations exceeding those for the colon Bacillus by 3-4 orders. Besides, a toxic effect of number of freshly isolated Proteus strains on the epithelial cells of intestine mucosa is observed. Strains isolated from patients with diarrhea and from environment differed from each other in the studied criteria. A conclusion is drawn that at the initial stage of the interaction with the intestine mucosa the Proteus strains differ considerably from the indigenous strain of the colon Bacillus in the ability to colonize the epithelial surface.     

喷司他丁的合成及其生物合成机制研究进展

喷司他丁是一种核苷类抗生素,对腺苷脱氨酶有极强的抑制效果,在临床治疗恶性肿瘤方面具有广泛应用。但其生产成本高、市售价格昂贵,难以满足需求。近10年来,关于生物合成喷司他丁的研究主要集中在菌种选育、优化培养基组分与发酵工艺等方面。目前,尽管喷司他丁的生物合成机制得到了阐明,但生物合成喷司他丁方面的综述尚无。对此,文中综述了喷司他丁的生物合成进展,为其进一步研究提供参考。首先,简介了喷司他丁的合成方法及其生产现状;其次,总结了喷司他丁在不同微生物中的生物合成机制;最后,探讨了生物合成喷司他丁所面临的问题,并提出调控微生物合成喷司他丁的策略,以期为喷司他丁的规模化生产提供指导。     

Interaction of PC-3 cells with fibronectin adsorbed on sulfonated polystyrene surfaces

The ability of cancer cells to invade neighboring tissues is crucial for cell dissemination and tumor metastasis. It is generally assumed that cell adhesion to extracellular matrix proteins is an important stage of cancer progression. Hence, adhesion of cancer cells under in vitro conditions to proteins adsorbed on a substratum surface has been studied to provide a better understanding of cell-protein interaction mechanisms. A protein, adsorbed in an appropriate conformation on a substratum surface, creates a biologically active layer that regulates such cell functions as adhesion, spreading, proliferation and migration. In our study, we examined the interaction of PC-3 cells under in vitro conditions with fibronectin adsorbed on sulfonated polystyrene surfaces of a defined chemical composition and topography. We investigated cell adhesion to fibronectin and cell spreading. Using automatic, sequential microscopic image registration, we are the first to present observations of the dynamics of PC-3 cell spreading and the cell shape during this process. Our results show that cell adhesion and the shape of spreading cells strongly depend on the time interaction with fibronectin. The analysis of images of cytoskeletal protein distribution in the cell region near the cell-substratum interface revealed that induction of a signal cascade took place, which led to the reorganization of the cytoskeletal proteins and the activation of focal adhesion kinase (FAK).     

Antimicrobial peptides from marine invertebrates: challenges and perspectives in marine antimicrobial peptide discovery

The emergence of pathogenic bacteria resistance to conventional antibiotics calls for an increased focus on the purification and characterization of antimicrobials with new mechanisms of actions. Antimicrobial peptides are promising candidates, because their initial interaction with microbes is through binding to lipids. The interference with such a fundamental cell structure is assumed to hamper resistance development. In the present review we discuss antimicrobial peptides isolated from marine invertebrates, emphasizing the isolation and activity of these natural antibiotics. The marine environment is relatively poorly explored in terms of potential pharmaceuticals, and it contains a tremendous species diversity which evolved in close proximity to microorganisms. As invertebrates rely purely on innate immunity, including antimicrobial peptides, to combat infectious agents, it is believed that immune effectors from these animals are efficient and rapid inhibitors of microbial growth.     

胱氨酸/半胱氨酸调控活性氧代谢影响大肠杆菌耐药性

【背景】随着越来越多超级细菌出现和抗生素资源的渐渐枯竭,细菌耐药机制研究愈加重要。【目的】探讨大肠杆菌内源半胱氨酸推动Fenton反应,调控胞内的活性氧水平,从而影响细菌耐药性这一代谢途径。【方法】在贫硫的培养条件下,通过控制外源胱氨酸和抗生素浓度,研究了胱氨酸/半胱氨酸对大肠杆菌耐药性的影响。【结果】较低水平的半胱氨酸使大肠杆菌对抗生素的耐药性增强,RNA-Seq的结果证明了胱氨酸内流对Fur、CysB和SOS的调控作用。LC-MS对外流硫醇的分析显示,细胞会快速将过量内流的半胱氨酸泵出胞外。在抗生素一定浓度范围内,半胱氨酸外排泵AlaE表现出良好的细胞保护作用。【结论】大肠杆菌对不同作用机理抗生素硫酸庆大霉素、氨苄青霉素和诺氟沙星的耐药性均受内源半胱氨酸水平的影响。本文通过研究半胱氨酸调控活性氧代谢对大肠杆菌耐药性的影响,为探讨细菌耐药性机制提供新的理论依据。     

Study of microbial adhesion on some wood species: Theoretical prediction

The initial interaction between microorganisms and substrata is mediated by physicochemical forces, which in turn originate from the physicochemical surface properties of both interacting phases. In this context, we have determined the physicochemical proprieties of all microorganisms isolated from cedar wood decay in an old monument at the Medina of Fez-Morocco. The cedar wood was also assayed in terms of hydrophobicity and electron donor-electron acceptor (acid-base) properties. Investigations of these two aspects were performed by contact angles measurements via sessile drop technique. Except Bacillus subtilis strain (Giwi < 0), all strains studied showed positive values of the degree of hydrophobicity (Giwi > 0) and can therefore be considered as hydrophilic while cedar wood revealed a hydrophobic character (Giwi = 58.81 mJ m⁻²). All microbial strains were predominantly electron donor. The results show also that all strains were weak electron acceptors. Cedar wood exhibits a weak electron donor/acceptor character. Based on the thermodynamic approach, the Lifshitz-van der Waals interaction free energy, the acid-basic interactions free energy, the total interaction free energy between the microbial cells and six different wood species (cedar, oak, beech, ash, pine and teak) in aqueous media was calculated and used to predict which microbial strains have a higher ability to adhere to wooden surfaces. Except of weak wood, for all the situations studied, generalizations concerning the adhesion of the microbiata on wood species cannot be made and the microbial adhesion on wooden substrata was dependent on wood species and microorganisms tested.     

Inhibition of Pseudomonas aeruginosa adhesion to fibronectin by PA-IL and monosaccharides: involvement of a lectin-like process

Pseudomonas aeruginosa adherence to fibronectin has been shown to be important to bacterial colonization and infection. To better understand the mechanisms involved in this interaction, the role of the carbohydrate moiety of the fibronectin molecule in P. aeruginosa adhesion was studied. Strain NK 125 502 adhered to immobilized fibronectin with an adherence index of 4.8 x 10(5) CFU/ micro g. Periodic oxidation of fibronectin markedly reduced the adhesion of P. aeruginosa, while a neuraminidase treatment increased bacteria adhesion. N-Acetylgalactosamine, N-acetylglucosamine, sialic acid, and also lectin PA-IL worked as efficient inhibitors in adhesion assays: 59%, 70.7%, 100%, and 60% of inhibition, respectively. We have demonstrated here the involvement of a lectin-like process in the interaction of P. aeruginosa NK 125 502 with immobilized fibronectin.     

益生菌调控幼龄畜禽消化道微生物研究进展

益生菌是一类对宿主(人类或动物)有益的活性微生物,包括细菌、真菌(如酵母)等,具有促进动物生长、提高免疫力的作用,是潜在的抗生素替代品。益生菌可能通过与动物消化道微生物互作来发挥益生作用,但具体机制仍不明确。综述了基于高通量测序技术研究益生菌调控幼龄畜禽(仔猪、雏鸡、反刍动物)消化道微生物群落组成的最新进展,并提出了未来研究方向,包括益生菌如何通过与消化道微生物互作影响其功能,益生菌对于幼龄畜禽不同健康状态下肠道微生物的影响,以及宿主因素如何影响益生菌对于幼龄畜禽消化道微生物的作用效果。     

The adhesion of pathogenic microflora on carbon sorbents

The adsorbing activity of granulated carbonic sorbents SKN and KAU, as well as their oxidated forms, containing protogenic carboxylic and phenolic groups with respect to Shigella flexneri, Salmonella typhimurium, Escherichia coli, Streptococcus aureus and Pseudomonas aeruginosa pathogenic strains has been studied. As shown in this study, the process of interaction between microorganisms and carbonic sorbents has two stages. At the first stage the main role is played by long-distance electrostatic forces and at the second stage, by Van der Waals short-distance forces, as well as bonds formed between cell structures and surface groupings of carbonaceous materials. In the mechanism of interaction between microbial cells and carbons the geometry of carbon surface plays an important role. KAU(0)-1 exhibits the highest degree of adhesion with respect to pathogenic bacteria.     

Real time monitoring of the effects of Heparan Sulfate Proteoglycan (HSPG) and surface charge on the cell adhesion process using thickness shear mode (TSM) sensor

The effects of Heparan Sulfate Proteoglycan (HSPG) and surface charge on the cellular interactions of the cell membrane with different substrates to determine the kinetics of cell adhesion was studied using thickness shear mode (TSM) sensor. The TSM sensor was operated at its first, third, fifth and seventh harmonics. Since the penetration depth of the shear wave decreases with increases in frequency, the multi-resonance operation of the TSM sensor was used to monitor the changes in the kinetics of the cell-substrate interaction at different distances from the sensor surface. During the sedimentation and the initial attachment of the cells on the sensor surface, the changes in the sensor resonant frequency and the magnitude response were monitored. First, HSPGs were partially digested with the enzyme Heparinase III to evaluate the effect of HSPG on the cell adhesion process. The results indicated that HSPG did not have any effect on the kinetics of the initial attachment, but it did reduce the strength of steady-state cell adhesion. Next, we investigated the effect of the electrostatic interactions of the cell membrane with the substrate on the cell adhesion. In this case, the sensor surface was coated with positively charged Poly-D-Lysine (PDL). It was observed that electrostatic interaction of the negatively charged cell membrane with the PDL surface promoted the initial cell adhesion but did not support long-term cell adhesion. The multi-resonant TSM technique was shown to be a very promising method for monitoring specific interfacial effects involving in cell adhesion process in real-time.     

A role for the Ca2(+)-dependent adhesion molecule, N-cadherin, in myoblast interaction during myogenesis

The formation of multinucleate skeletal muscle cells (myotubes) is a Ca2(+)-dependent process involving the interaction and fusion of mononucleate muscle cells (myoblasts). Specific cell-cell adhesion precedes lipid bilayer union during myoblast fusion and has been shown to involve both Ca2(+)-independent (CI)2 and Ca2(+)-dependent (CD) mechanisms. In this paper we present evidence that CD myoblast adhesion involves a molecule similar or identical to two known CD adhesion glycoproteins, N-cadherin and A-CAM. These molecules were previously identified by other laboratories in brain and cardiac muscle, respectively, and are postulated to be the same molecule. Antibodies to N-cadherin and A-CAM immunoblotted a similar band with a molecular weight of approximately 125,000 in extracts of brain, heart, and pectoral muscle isolated from chick embryos and in extracts of muscle cells grown in vitro at Ca2+ concentrations that either promoted or inhibited myotube formation. In assays designed to measure the interaction of fusion-competent myoblasts in suspension, both polyclonal and monoclonal anti-N-cadherin antibodies inhibited CD myoblast aggregation, suggesting that N-cadherin mediates the CD aspect of myoblast adhesion. Anti-N-cadherin also had a partial inhibitory effect on myotube formation likely due to the effect on myoblast-myoblast adhesion. The results indicate that N-cadherin/A-CAM plays a role in myoblast recognition and adhesion during skeletal myogenesis.     

Applications from bacterial adhesion and biofilm studies in relation to urogenital tissues and biomaterials: A review

Summary The urogenital tract, particularly of the adult female, is the habitat for many species of microorganisms. These populations are in a state of flux, are susceptible to disruption by antibiotics and spermicides, and are exposed to many different biomaterial substrata. Infections of the genital area and bladder are common, and are invariably initiated by microbial adhesion to surfaces. This review examines the actual and potential applications to industry and to patients emerging from the study of bacterial adhesion to surfaces.     

根系分泌物介导的根际效应及在水体生态修复中的应用潜力

文章主要以根系分泌物为核心, 综述了根系分泌物的分类、发生机理及影响因素; 围绕着植物-土壤-微生物三者的关系, 阐述了根系分泌物介导的植物与植物之间的化感作用、植物与根际微生物之间的协同作用以及植物微生物相互作用对土壤物质循环的影响。水生植物以其生境的特殊性和功能的不可替代性, 对沉积物污染物去除和水体生态修复产生显著的影响。在水体生态问题较为严峻的今天, 充分认识水生植物根系分泌物介导的根际过程将为水生植物生态学和水体生态修复领域的发展提供基础, 并为学科应用潜力的开发提供依据。