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PubMed2003

[Antiinfective host defense mechanism: toll-like receptors and innate immunity].

The innate immune system has evolved as the first line of defense against invading microorganisms. The recent discovery of the toll-like receptors(TLRs) has rapidly expanded our knowledge of molecular events that initiate host-pathogen interactions. The TLRs, which are expressed on the surface of cells, involved in innate immune recognition, including macrophages and dendritic cells, have a crucial role in the detection of microbial infection. Signals initiated by the interaction of TLRs with pathogen-associated molecular patterns (PAMPs) induce activation of the inflammatory and antimicrobial innate immune response. Ten members of the TLR family have been identified, and they appear to recognize PAMPs, including lipopolysaccharide, peptidoglycan, and bacterial DNA. There has been considerable interest in how adaptive immune responses are controlled by the innate immune system. Recent studies have suggested that TLRs may control the induction of Th1 responses and that a separate system of recognition regulates the Th2 response. Thus TLR signaling represents a key component in the innate immune response to microbial infection.

Animals↗
PubMed2006

Biofiltration and inhibitory interactions of gaseous benzene, toluene, xylene, and methyl tert-butyl ether.

This study evaluated the individual and combined removal capacities of benzene, toluene, and xylene (B, T, and X) in the presence and absence of methyl tert-butyl ether (MTBE) in a polyurethane biofilter inoculated with a BTX-degrading microbial consortium, and further examined their interactive effects in various mixtures. In addition, Polymerase chain reaction-denaturing gradient gel electrophoresis and phylogenetic analysis of 16S rRNA gene sequences were used to compare the microbial community structures found in biofilters exposed to the various gases and gas mixtures. The maximum individual elimination capacities (MECs) of B, T, and X were 200, 238, and 400 g m(-3) h(-1), respectively. There was no significant elimination of MTBE alone. Addition of MTBE decreased the MECs of B,T, and X to 75, 100, and 300 g m(-3) h(-1), respectively, indicating that benzene was most strongly inhibited by MTBE. When the three gases were mixed (B + T + X), the removal capacities of individual B, T, and X were 50, 90, and 200 g m(-3) h(-1), respectively. These capacities decreased to 40, 50, and 100 g m(-3) h(-1) when MTBE was added to the mix. The MEC of the three-gas mixture (B + T + X) was 340 g m(-3) h(-1), and that of the four-gas mixture was 200 g m(-3) h(-1). Although MTBE alone was not degraded by the biofilter, it could be co-metabolically degraded in the presence of toluene, benzene, or xylene with the MECs of 34, 23, and 14 g m(-3) h(-1), respectively. The microbial community structure analysis revealed that two large groups could be distinguished based on the presence or absence of MTBE, and many of the dominant bacteria in the consortia were closely related to bacteria isolated from aromatic hydrocarbon-contaminated sites and/ or oil wastewaters. These findings provide important new insights into biofiltration and may be used to improve the rational design of biofilters for remediation of petroleum gas-contaminated airstreams according to composition types of mixed gases.

Air Pollutants↗
PubMed2005

Microbial community activities during establishment, performance, and decline of bench-scale passive treatment systems for mine drainage.

Permeable reactive barrier (PRB) technology, in which sulfate-reducing bacteria (SRB) facilitate precipitation of metal sulfides, is a promising approach for remediation of sulfate- and metal-laden mine drainage. While PRBs are easily established, they often decline for reasons not well understood. SRB depend on or compete with multiple dynamic microbial populations within a PRB; as a result, performance depends on the changing PRB chemical composition and on succession and competition within the microbial community. To investigate these interactions, we constructed and monitored eight bench-scale PRBs to define periods of establishment, performance, and decline. We then conducted short-term batch studies, using substrate-supplemented column materials, on Days 0 (pre-establishment), 27 (establishment), 41 (performance), and 99 (decline) to reveal potential activities of cellulolytic bacteria, fermenters + anaerobic respirers, SRB, and methanogens. PRBs showed active sulfate reduction, with sulfate removal rates (SRR) of approximately 1-3 mol/m3/d, as well as effective removal of Zn2+. Potential activities of fermentative + anaerobic respiratory bacteria were initially high but diminished greatly during establishment and dropped further during performance and decline. In contrast, potential SRB activity rose during establishment, peaked during performance, and diminished as performance declined. Potential methanogen activity was low; in addition, SRB-methanogen substrate competition was shown not to limit SRB activity. Cellulolytic bacteria showed no substrate limitation at any time. However, fermenters experienced substrate limitation by Day 0, SRB by Day 27, and methanogens by Day 41, showing the dependence of each group on upstream populations to provide substrates. All potential activities, except methanogenesis, were ultimately limited by cellulose hydrolysis; in addition, all potential activities except methanogenesis declined substantially by Day 99, showing that long-term substrate deprivation strongly diminished the intrinsic capacity of the PRB community to perform.

Alkalies↗
PubMed2004

Bacterial surface characteristics applied to selection of probiotic microorganisms.

For the study of probiotic microorganisms, the in vitro selection tests need to be based on a solid scientific foundation. Surface characteristics, one of the in vitro properties are used to evaluate the potentially probiotic strains of lactobacilli. Bacterial surface properties have been associated with attachment to a variety of substrata. Bacterial adhesion to tissues is considered the first step, and such adhesion can also determine the colonization capability of a microorganism. Through adhesion ability and colonization of tissues, probiotic microorganisms can prevent pathogen access by steric interactions or specific blockage on cell receptors. One of the main characteristics studied is the hydrophobic nature of the bacterial cell surface. To test this property, Rosenberg and Doyle divided microbial cell hydrophobicity assays into two categories. The first includes contact angle measurements (CAMs), partitioning of cells into one or another liquid phase (TTP), and adsorption of individual hydrophobic molecular probes at the cell surface. The second category includes microbial adhesion to hydrocarbons (MATH), hydrophobic interaction chromatography (HIC), and adhesion to polystyrene and other hydrophobic solid surfaces. The tests included in the first category measure hydrophobic properties of the outer cell surface as a whole; those in the second measure hydrophobicity in terms of adhesion. Finally, those bacterium classified as hydrophobic can be considered as able to mediate adhesion. The objective of this chapter is to describe three different methods applied in our laboratory for the study of bacterial surface properties. They can be used to screen characteristics of lactobacillus strains for probiotic purposes. They are: Microbial adhesion to hydrocarbons (MATH); Salt aggregation test (SAT); Hemagglutination (HA) reaction.

Animals↗
PubMed2005

Lactoferrin: an important host defence against microbial and viral attack.

The first function attributed to lactoferrin (Lf), an iron binding protein belonging to the non-immune natural defences, was antimicrobial activity that depended on its capacity to sequester iron. Iron-independent microbicidal activities, requiring direct interaction between this cationic protein and microbial surface components, were later demonstrated. Many other anti-microbial and anti-viral functions have since been ascribed to Lf. In mucosal secretions, iron and Lf modulate the motility and aggregation of pathogenic bacteria. Lf inhibits bacterial adhesion on abiotic surfaces through ionic binding to biomaterials, or specific binding to bacterial structures or both. Lf inhibition of bacterial adhesion to host cells requires Lf binding to bacteria and/or host cells. Lf hinders microbial internalization by binding to both glycosaminoglycans and bacterial proteins which can be degraded by Lf-mediated proteolysis. Moreover, Lf internalisation and localisation to the host cell nuclei could modulate bacterial entry into cells through gene regulation. Finally, the capability of Lf to exert antiviral activity, through its binding to host cells and/or viral particles, strengthens the idea that it is an important brick in the mucosal wall, effective against both microbial and viral attacks.

Animals↗
PubMed1998

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.

Bacterial Adhesion↗
PubMed2005

Assessing interactions of multiple agrichemicals by using bacterial assemblages in a wetland mesocosm system.

Agrichemicals may enter wetlands located adjacent to or downstream from agricultural fields. We investigated the individual and interactive effects of three agrichemicals [atrazine, chlorpyrifos, and monosodium acid methanearsonate (MSMA)] and methyl mercury on abundance and heterotrophic potential of wetland heterotrophic bacteria assemblages. We used a factorial experimental design, in which chemicals were introduced in all possible combinations to 66 500-liter mesocosms at the Biological Field Station of the University of Mississippi. Methyl mercury was added to bring the total mercury (HG) concentration to 0.4 mg/Kg wet weight at the sediment surface. Atrazine, chlorpyrifos, and MSMA were added at concentrations of 192, 51, and 219 microg/L, respectively. Over 32 days of exposure, microbial heterotrophic activity was sensitive to only the interactive effect of HG*ATR*CPF in the sediments and only CPF in the water. Total bacterial numbers did not exhibit any significant treatment effects. Therefore, the effects of agrichemicals were reflected on cell-specific bacterial heterotrophic activity rather than bacterial population size.

Agrochemicals↗
PubMed2004

Pine genes regulated by the necrotrophic pathogen Fusarium circinatum.

A targeted genomics approach was used to construct a cDNA array of potential pathogen-regulated genes for investigating host-pathogen interactions in pine trees (Pinus species). This array, containing a nonredundant set of 311 cDNAs, was assembled by combining smaller sets of cDNAs generated by differential display or suppression subtraction hybridization using a variety of pathogen treatments and elicitors. The array was probed to identify host genes regulated by Fusarium circinatum, a necrotrophic fungus that incited pitch canker disease on pine stems. A set of 29 cDNAs were induced during the disease state. Notably, cDNAs on the array that were derived from experiments with fusiform rust, incited by Cronartium quercuum f. sp. fusiforme (a biotrophic fungus) were unregulated by Fusarium. the results imply distinct genetic responses in pine to diseases incited by necrotrophs and biotrophs. This cDNA collection expands the genomics toolkit for understanding interactions between conifers and their microbial associates in forest ecosystems.

Base Sequence↗
PubMed2006

New thoughts on the pathobiology of regimen-related mucosal injury.

BACKGROUND: Our understanding of the biological basis for mucosal barrier injury (mucositis) induced by cancer therapy with radiation or drugs continues to evolve. A patient's mucosal response to cancer therapy appears to be controlled by both global (i.e. gender, underlying systemic disease, race) and tissue specific (i.e. epithelial type, intrinsic endocrine system, local microbial environment, function) factors. CONCLUSION: Interactions of these elements, coupled with underlying genetic influences, most likely govern the risk, course and severity of regimen-related mucosal injury.

Antineoplastic Agents↗
PubMed2004

A plasmid immunization construct encoding urease B of Helicobacter pylori induces an antigen-specific antibody response and upregulates the expression of beta-defensins and IL-10 in the stomachs of immunized mice.

The objectives of this study were to investigate the efficacy of a prototype DNA immunization construct encoding the urease B subunit enzyme of Helicobacter pylori (H. pylori) for inducing adaptive and innate immune responses in mice immunized via intramuscular or subcutaneous routes and to further explore the adjuvant effects of the CpG motifs in the vector. Antibody, cytokine, and beta-defensin profiles were assessed in the stomachs of immunized animals: experiments were terminated 3 months after immunization because there was a significant increase in the anti-H. pylori urease B antibody response at Week 6 in mice immunized with the urease B construct. A long lasting expression of IL-10 mRNA was noted. Furthermore, a marked and sustained increase in the mRNA expression of beta-defensins was also observed, particularly beta1. This study demonstrates that an H. pylori urease B DNA construct can induce innate as well as adaptive immune responses in the stomachs of immunized mice. Upregulation of beta-defensin gene expression followed immunization and we believe that this is the first report of a DNA vaccine inducing innate anti-microbial responses. Such complex molecular interactions that modulate both innate and adaptive immune responses may be of critical importance in the control of mucosal pathogens, such as H. pylori.

Animals↗
PubMed2000

Intercellular adhesion molecule-1 (ICAM-1) expression and cell signaling cascades.

The collective interaction between cells is, in part, mediated by different families of adhesion molecules. Intercellular adhesion molecules (ICAMs) are structurally related members of the immunoglobulin supergene family and are ligands for the beta2 integrin molecules present on leukocytes. Of the five ICAMs identified, ICAM-1 is the most extensively studied. Although ICAM-1 is expressed constitutively at low levels on endothelial cells and on some lymphocytes and monocytes, its expression can be significantly increased in the presence of cytokines (TNFalpha, IL-1, IFNgamma) and reactive oxygen species. Depending upon cell type, ICAM-1 participates in trafficking of inflammatory cells, in cell:cell interactions during antigen presentation, in microbial pathogenesis, and in signal transduction through outside-in signaling events. Again, depending upon cell type examined, ICAM-1 engagement has been documented to activate specific kinases through phosphorylation, resulting in transcription factor activation and increased cytokine production, increased cell membrane protein expression, reactive oxygen species production, and cell proliferation.

Animals↗
PubMed2002

Resilience of the rhizosphere to anthropogenic disturbance.

The rhizosphere is a dominant site of microbial metabolism in soil and whereas it can be shown that anthropogenic disturbances can influence this metabolism, the impact of these disturbances on biodiversity is rather difficult to determine at the species level. This is in part because no more than 10% of the microbial species are culturable, and in part because there is very poor precision in plate counting, usually requiring a change of 300-500% to be significant. We have therefore used a functional approach. The 'ecophysiological index' is based on r or K strategy of the organisms being counted. Also, enzyme families, microbial biomass, microbe/microbe and microbe/fauna interactions have been determined, along with nutrient uptake measurements. The techniques have been applied to determine the effects of disturbances created by the introduction of GM plants and microorganisms to soil, these effects being small compared with those caused by time-honoured practices such as crop rotation and ploughing. Toxicity from industrial influences (e.g. cyanide) can be remediated by rhizosphere microorganisms.

Animals↗
PubMed2005

Skewed T-cell receptor BV14 and BV16 expression and shared CDR3 sequence and common sequence motifs in synovial T cells of rheumatoid arthritis.

T-lymphocytes play an important role in rheumatoid arthritis (RA). In this study, we evaluated the hypothesis that common T-cell receptor (TCR) structural features may exist among infiltrating T cells of different RA patients, if the TCR repertoire is shaped by interaction with common self or microbial antigens in the context of susceptible HLA genes in RA. Synovial lesion tissue (ST), synovial fluid (SF) and blood specimens from RA patients and controls were analyzed for TCR V gene repertoire by real-time PCR. There was highly skewed BV14 and BV16 usage in synovial T cells of RA as opposed to those of controls, which was accompanied with a trend for correlation between skewed BV16 and DRB1(*)0405. Immunoscope analysis of the V-D-J region of ST-derived T cells demonstrated oligoclonal and polyclonal expansion of BV14(+) and BV16(+) T cells. Detailed characterization using specific BV and BJ primers further revealed common clonotypes combining the same BV14/BV16, BJ and CDR3 length. DNA cloning and sequence analysis of the clonotypes confirmed identical CDR3 sequences and common CDR3 sequence motifs among different RA patients. The findings are important in the understanding of BV gene skewing and CDR3 structural characteristics among synovial infiltrating T cells of RA.

Arthritis, Rheumatoid↗
PubMed2001

Low-level antibacterial resistance: a gateway to clinical resistance.

The huge amount of antibiotic substances released in the human environment has probably resulted in an acceleration in the rate of bacterial evolution. It is to note that most interactions between chemotherapeutic agents and microbial populations occur at very low antibiotic concentrations. Thus, natural selection is expected to act on very small increases in the bacterial ability to resist to antibiotic inhibitory effects. On the other hand, there is a wealth of mechanisms to resist to these low antibiotic concentrations. The progressive enrichment in low-level resistant populations favours secondary selections for more specific and effective mechanisms of resistance, particularly in treated patients. These adaptations may have a biological cost in the absence of antibiotics, but frequently compensatory mutations occur, minimizing such genetic burden. In this way, a phenomenon of directional selection takes place, with low possibilities of return to susceptibility. Moreover, low antibiotic concentrations are not only able to select low-level antibiotic resistant variants, but may produce a substantial stress in bacterial populations, that eventually influences the rate of genetic variation and the diversity of adaptive responses. More attention should be devoted to the mechanisms of low-level resistance in microorganisms, as they can serve as stepping stones to develop high level, clinically relevant resistance. These mechanisms should be identified early in the development of drugs in order to adapt the therapeutic strategies (for instance dosage) to minimize the selection of low-level resistant variants, as frequently they emerge by means of concentration-specific selection. At the same time, conventional susceptibility testing should probably be able to detect low-level resistance, and not only clinically-relevant resistance. We should be vigilant of the evolutionary trends of microorganisms; for that a purpose, knowledge of the biology and epidemiology of low-level resistance is becoming a real need.

Animals↗
PubMed2003

Mpi recombinase globally modulates the surface architecture of a human commensal bacterium.

The mammalian gut represents a complex and diverse ecosystem, consisting of unique interactions between the host and microbial residents. Bacterial surfaces serve as an interface that promotes and responds to this dynamic exchange, a process essential to the biology of both symbionts. The human intestinal microorganism, Bacteroides fragilis, is able to extensively modulate its surface. Analysis of the B. fragilis genomic sequence, together with genetic conservation analyses, cross-species cloning experiments, and mutational studies, revealed that this organism utilizes an endogenous DNA inversion factor to globally modulate the expression of its surface structures. This DNA invertase is necessary for the inversion of at least 13 regions located throughout the genome, including the promoter regions for seven of the capsular polysaccharide biosynthesis loci, an accessory polysaccharide biosynthesis locus, and five other regions containing consensus promoter sequences. Bacterial DNA invertases of the serine site-specific recombinase family are typically encoded by imported elements such as phage and plasmids, and act locally on a single region of the imported element. In contrast, the conservation and unique global regulatory nature of the process in B. fragilis suggest an evolutionarily ancient mechanism for surface adaptation to the changing intestinal milieu during commensalism.

Bacterial Capsules↗
PubMed1996

The PR5K receptor protein kinase from Arabidopsis thaliana is structurally related to a family of plant defense proteins.

We have isolated an Arabidopsis thaliana gene that codes for a receptor related to antifungal pathogenesis-related (PR) proteins. The PR5K gene codes for a predicted 665-amino acid polypeptide that comprises an extracellular domain related to the PR5 proteins, a central transmembrane-spanning domain, and an intracellular protein-serine/threonine kinase. The extracellular domain of PR5K (PR5-like receptor kinase) is most highly related to acidic PR5 proteins that accumulate in the extracellular spaces of plants challenged with pathogenic microorganisms. The kinase domain of PR5K is related to a family of protein-serine/threonine kinases that are involved in the expression of self-incompatibility and disease resistance. PR5K transcripts accumulate at low levels in all tissues examined, although particularly high levels are present in roots and inflorescence stems. Treatments that induce authentic PR5 proteins had no effect on the level of PR5K transcripts, suggesting that the receptor forms part of a preexisting surveillance system. When the kinase domain of PR5K was expressed in Escherichia coli, the resulting polypeptide underwent autophosphorylation, consistent with its predicted enzyme activity. These results are consistent with PR5K encoding a functional receptor kinase. Moreover, the structural similarity between the extracellular domain of PR5K and the antimicrobial PR5- proteins suggests a possible interaction with common or related microbial targets.

Amino Acid Sequence↗
PubMed2003

Cellular recognition of tri-/di-palmitoylated peptides is independent from a domain encompassing the N-terminal seven leucine-rich repeat (LRR)/LRR-like motifs of TLR2.

Toll-like receptors (TLRs) mediate microbial pattern recognition in vertebrates. A broad variety of agonists has been attributed to TLR2 and three TLRs, TLR4, TLR2, and TLR5, have been demonstrated to bind microbial products. Distinct agonists might interact with different subdomains of the TLR2 extracellular domain. The TLR2 extracellular domain sequence includes 10 canonical leucine-rich repeat (LRR) motifs and 8-10 additional and potentially functionally relevant LRR-like motifs. Thus, the transfection of TLR2 LRR/LRR-like motif deletion constructs in human embryonic kidney 293 cells and primary TLR2-deficient mouse fibroblasts was performed for analysis of the role of the regarding domains in specific pattern recognition. Preparations applied as agonists were highly purified soluble peptidoglycan, lipoteichoic acid, outer surface protein A from Borrelia burgdorferi, synthetic mycoplasmal macrophage-activating lipoprotein-2, tripalmitoyl-cysteinyl-seryl-(lysyl)3-lysine (P3CSK4), dipalmitoyl-CSK4 (P2-CSK4), and monopalmitoyl-CSK4 (PCSK4) as well as lipopolysaccharide and inactivated bacteria. We found that a block of the N-terminal seven LRR/LRR-like motifs was not involved in TLR2-mediated cell activation by P3CSK4 and P2CSK4 ligands mimicking triacylated and diacylated bacterial polypeptides, respectively. In contrast, the integrity of the TLR2 holoprotein was compulsory for effective cellular recognition of other TLR2 agonists applied, including PCSK4. The formation of a functionally relevant subdomain by a region including the N-terminal seven LRR/LRR-like motifs rather than by single LRRs is suggested by our results. They further imply that TLR2 contains multiple binding domains for ligands that may contribute to the characterization of its promiscuous molecular pattern recognition.

Amino Acid Motifs↗