Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “microbial interactions”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,621 records · Page 90Linked to original sources
PubMed2026

Endozoicomonas acroporae enhances coral thermal resilience through host-microbe coordination.

Probiotics hold promise for enhancing coral resilience under climate-driven thermal stress, yet their mechanisms remain poorly understood. Although the bacterial genus Endozoicomonas has been proposed to benefit corals, in vivo evidence of beneficial effects on the host remains limited. Here, we establish Endozoicomonas acroporae Acr-14T as a coral probiotic and characterize its effects on the reef-building coral Stylophora pistillata. We show that E. acroporae Acr-14T enhances host thermal tolerance, colonizes coral tissues, and forms coral-associated microbial aggregates. Microbial profiling indicates that probiotic treatment is associated with reduced relative abundances of opportunistic microbes and enrichment of putatively beneficial taxa. To support transcriptomic analyses, we assembled a chromosome-level genome of S. pistillata clade 1 (Pacific lineage) and found that E. acroporae Acr-14T treatment mitigates heat-induced protein-folding stress and apoptotic signaling. Single-cell transcriptomics further revealed altered expression of genes involved in S-adenosylmethionine (SAMe) metabolism and pro-survival signaling in gastrodermal cells of probiotic-treated corals. Together, our results provide a cell-type-resolved view of host responses linked to Endozoicomonas-mediated coral thermal resilience and offer insight into molecular mechanisms implicated in host-microbe interactions under environmental stress.

Animals↗
PubMed2005

Screening of molecular repertoires by microbial surface display.

A multitude of systems for the presentation of foreign peptides or proteins on the surface of microorganisms has been developed within the past two decades. However, the majority of the bacterial surface display systems are devoted to the presentation of heterologous antigens to the immune system (vaccine generation). Bacteria are the preferable hosts for the generation of vast genetic repertoires, and their genetic manipulation and cultivation is easy. As a consequence, they provide promising systems for large-scale functional screenings, e.g. for enzyme activity or protein-protein interactions. This review will focus on examples of microbial surface display used for the screening of combinatorial repertoires. Further, we discuss future opportunities and promising candidate proteins not yet employed for that task.

Antibody Affinity↗
PubMed1991

A potential role for microbial superantigens in the pathogenesis of systemic autoimmune disease.

We have attempted herein to demonstrate how microbial superantigens could promote an abnormal form of "cognate" T helper-B cell interaction, analogous to that which may occur during GVH disease, leading to B cell activation and systemic autoimmunity. In vitro studies performed at our laboratory and others have demonstrated that resting human B cells bind microbial superantigens and present them to superantigen-reactive autologous T helper cells, resulting in T cell activation and polyclonal IgM and IgG production by the superantigen-bearing B cells. In vitro studies of microbial superantigen-mediated murine T helper-B cell interactions demonstrate preferential help for B cells that have encountered specific antigen. Both in humans and in mice, the cellular interactions involved and the B cell responses induced are highly analogous to those mediated by allospecific T helper-B cell interaction. Finally, the results of studies carried out on T cell-deficient (nude) mice suggest that microbial superantigens may trigger similar T helper cell-dependent polyclonal IgM and IgG responses in vivo. These mice will be studied over time and tested for the development of autoantibodies characteristic of SLE and of autoimmune organ system damage, the occurrence of which are predicted by our model.

Antigens, Bacterial↗
PubMed2000

Flow cytometric analysis of microorganisms.

The application of flow cytometry to microorganisms is as old as the technique itself, but it has historically been underexploited for microbial applications. This is now being reversed and microbiologists are ideally placed to benefit from recent technological advances. While earlier papers demonstrated the use of flow cytometry for studies of viability and taxonomy, recent developments in bioinformatics and reporter gene technologies are leading to novel applications in microbiology. Variants of green fluorescent protein have been used for the study of conditional microbial gene regulation in medically important host-pathogen interactions and fluorescence-activated cell sorting is being applied to the isolation of novel mutants in directed evolution studies. This paper reviews the reasons for the delay in the application of flow cytometry to microbial problems, the range of applications, and their limitations and considers the progress made in developing new strategies for use in microbiological investigations.

Bacteria↗
PubMed1993

Effect of synchronization of energy and nitrogen supply on ruminal characteristics and microbial growth.

The effect of energy and N synchronization in the rumen on microbial growth was investigated. The same daily amount of readily available energy and N sources (19 g of ruminally degradable N/kg of fermentable OM) was supplied intraruminally to sheep, according to different patterns, namely both energy and N as 12-hourly pulse-doses (fast synchronized supply), energy as 12-hourly pulse-doses and N as a continuous infusion (unsynchronized supply), energy as a continuous infusion and N as 12-hourly pulse doses (unsynchronized supply), and both energy and N as continuous infusions (slow synchronized supply). The study was done near maintenance (Exp. 1) and at a higher level of nutrition (Exp. 2). The degree of energy and N synchronization affected neither microbial flow nor efficiency of growth (P > .2 for energy x N interaction). Continuous infusion of energy resulted in a 17% (P < .05) and 14% (P = .18) higher efficiency of microbial growth than did pulse dosing in Exp. 1 and 2, respectively. This coincided with lower (P < .01) ruminal pH and higher (P < .05) ruminal lactic acid concentration for energy pulse-dose treatments. The results suggest that merely improving the degree of synchronization between energy and N release rates in the rumen does not increase microbial yield. Dietary manipulation, rather, should be aimed at first obtaining the most even ruminal energy supply pattern, and then at providing the appropriate amount of ruminally available N. Thereafter some further advantage may be gained in also ensuring a more even N supply pattern, particularly avoiding too rapid a ruminal N release.

Ammonia↗
PubMed1988

Modulation of major histocompatibility complex (MHC) expression by interferons and microbial agents. Independent regulation of MHC class II expression and induction of tumoricidal activity in bone marrow-derived mononuclear phagocytes.

In a pure population of rat bone marrow-derived mononuclear phagocytes (BMM phi), the expression of major histocompatibility complex (MHC) molecules and ability to manifest tumoricidal activity were simultaneously studied. Resting BMM phi, which express low levels of MHC class II molecules and do not manifest tumoricidal activity, become strongly MHC class II-positive, and evolve tumoricidal activity within 24 h when incubated with macrophage-activating lymphokines (MAF) or gamma interferon (IFN-gamma). In contrast, BMM phi which were interacted for 24 h with heat-killed microbial agents (Corynebacterium parvum, Listeria) evolve tumoricidal activity without parallel enhancement of MHC class II expression. IFN-alpha,beta neither induced tumoricidal activity nor enhanced MHC class II expression. Further experiments have shown that (a) the kinetics of MAF- and/or IFN-gamma-induced amplification of MHC class II expression and of tumoricidal activity are different; (b) enhancement of MHC class II expression by rIFN-gamma is not invariably paralleled by induction of tumoricidal activity; and (c) inhibitors of macrophage tumoricidal activity differ in their ability to affect MHC class II expression. It is concluded from these findings that in a population of pure BMM phi, i.e. in the complete absence of lymphocytes, the expression of MHC molecules and induction of tumoricidal activity are independently regulated phenomena; in particular, the enhanced expression of MHC class II molecules is not a prerequisite for induction and/or manifestation of tumoricidal activity by mononuclear phagocytes.

Adjuvants, Immunologic↗
PubMedDate not supplied

Antibacterial and cytotoxic effect of ceftazidime-mitoxantrone association.

Microbial infections are a major problem in tumor-bearing and in immunocompromised patients. In such conditions it is of paramount importance to know the possible interactions between anti-tumor and antimicrobial drugs. In the present work we investigated the relationship between Ceftazidime and Mitoxantrone. Ceftazidime and Mitoxantrone were tested alone and in combination for antibacterial activity against different strains of Gram- and Gram+ bacteria. The cytotoxic effect of combination Mitoxantrone-Ceftazidime was determined in cultured P388 leukemia cells. No interference with the antibacterial activity of Ceftazidime or with the cytotoxic activity of Mitoxantrone was observed.

Animals↗
PubMed2000

The chemical defense ecology of marine unicellular plankton: constraints, mechanisms, and impacts.

The activities of unicellular microbes dominate the ecology of the marine environment, but the chemical signals that determine behavioral interactions are poorly known. In particular, chemical signals between microbial predators and prey contribute to food selection or avoidance and to defense, factors that probably affect trophic structure and such large-scale features as algal blooms. Using defense as an example, I consider physical constraints on the transmission of chemical information, and strategies and mechanisms that microbes might use to send chemical signals. Chemical signals in a low Re, viscosity-dominated physical environment are transferred by molecular diffusion and laminar advection, and may be perceived at nanomolar levels or lower. Events that occur on small temporal and physical scales in the "near-field" of prey are likely to play a role in cell-cell interactions. On the basis of cost-benefit optimization and the need for rapid activation, I suggest that microbial defense system strategies might be highly dynamic. These strategies include compartmented and activated reactions, utilizing both pulsed release of dissolved signals and contact-activated signals at the cell surface. Bioluminescence and extrusome discharge are two visible manifestations of rapidly activated microbial defenses that may serve as models for other chemical reactions as yet undetected due to the technical problems of measuring transient chemical gradients around single cells. As an example, I detail an algal dimethylsulfoniopropionate (DMSP) cleavage reaction that appears to deter protozoan feeding and explore it as a possible model for a rapidly activated, short-range chemical defense system. Although the exploration of chemical interactions among planktonic microbes is in its infancy, ecological models from macroorganisms provide useful hints of the complexity likely to be found.

Animals↗
PubMed2002

Biodegradation kinetics of aromatic hydrocarbon mixtures by pure and mixed bacterial cultures.

Microbial growth on pollutant mixtures is an important aspect of bioremediation and wastewater treatment. However, efforts to develop mathematical models for mixed substrate kinetics have been limited. Nearly all models group either the microbial population (as "biomass") or the chemical species (e.g., as biological oxygen demand). When individual chemical species are considered, most models assume either no interaction or that the nature of the interaction is competition for the same rate-limiting enzyme. And when individual microbial species are considered, simple competition for the growth substrate is the only interaction included. Here, we present results using Pseudomonas putida F1 and Burkholderia sp. strain JS150 growing individually and together on benzene, toluene, phenol, and their mixtures and compare mathematical models to describe these results. We demonstrate that the simple models do not accurately predict the outcome of these biodegradation experiments, and we describe the development of a new model for substrate mixtures, the sum kinetics with interaction parameters (SKIP) model. In mixed-culture experiments, the interactions between species were substrate dependent and could not be predicted by simple competition models. Together, this set of experimental and modeling results presents our current state of work in this area and identifies challenges for future modeling efforts.

Biodegradation, Environmental↗
PubMed1993

Salivary protein interactions with oral bacteria: an electrophoretic study.

The relatively low levels of human salivary proteins in whole saliva as compared to the ductal secretions may be related to their interaction with oral bacteria. These interactions are thought to play an important role in the microbial colonisation of the mouth, and salivary proteins adsorbed to oral surfaces have been implicated in adherence. In this study we attempted to investigate the prevalence of interactive strains by screening a range of oral bacteria. Parotid saliva was incubated with bacterial suspensions and consequent alterations to the salivary protein profile determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). A number of salivary components were found to be preferentially removed, particularly by those species known to be primary colonizers of clean tooth surfaces.

Animals↗
PubMed2004

The gut bacteria of insects: nonpathogenic interactions.

The diversity of the Insecta is reflected in the large and varied microbial communities inhabiting the gut. Studies, particularly with termites and cockroaches, have focused on the nutritional contributions of gut bacteria in insects living on suboptimal diets. The indigenous gut bacteria, however, also play a role in withstanding the colonization of the gut by non-indigenous species including pathogens. Gut bacterial consortia adapt by the transfer of plasmids and transconjugation between bacterial strains, and some insect species provide ideal conditions for bacterial conjugation, which suggests that the gut is a "hot spot" for gene transfer. Genomic analysis provides new avenues for the study of the gut microbial community and will reveal the molecular foundations of the relationships between the insect and its microbiome. In this review the intestinal bacteria is discussed in the context of developing our understanding of symbiotic relationships, of multitrophic interactions between insects and plant or animal host, and in developing new strategies for controlling insect pests.

Animals↗
PubMed1999

The role of intermolecular interactions: studies on model systems for bacterial biofilms.

The mechanical stability of biofilms and other microbial aggregates is of great importance for both the maintenance of biofilm processes and the removal of undesired biofilms. The binding forces are weak interactions such as London dispersion forces, electrostatic interactions and hydrogen bonds. In a first attempt to rank their contribution, the viscosity of solutions of extracellular polymeric substances (EPS) from a mucoid strain of Pseudomonas aeruginosa is measured. In order to distinguish the binding forces, substances are chosen which individually address the different types of bonds. Polyacrylic acid is identified as a suitable model system for EPS when molecular interactions are studied. Electrostatic interactions and hydrogen bonds are found to be the dominating forces among macromolecules within the biofilm.

Acrylic Resins↗
PubMed2004

BCL10 mediates lipopolysaccharide/toll-like receptor-4 signaling through interaction with Pellino2.

Toll-like receptor (TLR) pathways signal through microbial components stimulation to induce innate immune responses. Herein, we demonstrate that BCL10, a critical molecule that signals between the T cell receptor and IkappaB kinase complexes, is involved in the innate immune system and is required for appropriate TLR4 pathway and nuclear factor-kappaB (NF-kappaB) activation. In response to lipopolysaccharide (LPS) stimulation, BCL10 was recruited to TLR4 signaling complexes and associated with Pellino2, an essential component down-stream of BCL10 in the TLR4 pathway. In a BCL10-deficient macrophage cell line, LPS-induced NF-kappaB activation was consistently defective, whereas activator protein-1 and Elk-1 signaling was intact. In addition, we found that BCL10 was targeted by SOCS3 for negative regulation in LPS signaling. The recruitment of BCL10 to TLR4 signaling complexes was attenuated by induced expression of SOCS3 in a feedback loop. Furthermore, ectopic SOCS3 expression blocked the interaction between BCL10 and Pellino2 together with BCL10-generated NF-kappaB activation and inducible nitric-oxide synthase expression. Together, these data define an important role of BCL10 in the innate immune system.

Adaptor Proteins, Signal Transducing↗
PubMed2002

Interactions between the microbiota and the intestinal mucosa.

The intestinal microflora can be considered as a postnatally aquired organ composed of a large diversity of bacterial cells that can perform different functions for the host. This organ is highly exposed to environmental influences and thus modulated in its composition and functions by external factors, such as nutrition. Specific components of the intestinal microflora, including lactobacilli and bifidobacteria, have been associated with beneficial effects on the host, such as promotion of gut maturation and integrity, antagonisms against pathogens and immune modulation. In addition, the microflora seem to play a significant role in the maintenance of intestinal immune homeostasis and prevention of inflammation. At the present time, the contribution of intestinal epithlial cell in the first line of defence against pathogenic bacteria and microbial antigens has been recognized, in contrast, the interactions of intestinal epithelial cells with commensal bacteria are less understood. The present work summarizes the increasing scientific attention for mechanisms of the innate immune response of the host to different components of the autochthonous microflora and suggests a potential role for selected probiotic bacteria in the regulation of intestinal inflammation.

Bifidobacterium↗
PubMed1995

Ferrichrome transport in Escherichia coli K-12: altered substrate specificity of mutated periplasmic FhuD and interaction of FhuD with the integral membrane protein FhuB.

FhuD is the periplasmic binding protein of the ferric hydroxamate transport system of Escherichia coli. FhuD was isolated and purified as a His-tag-labeled derivative on a Ni-chelate resin. The dissociation constants for ferric hydroxamates were estimated from the concentration-dependent decrease in the intrinsic fluorescence intensity of His-tag-FhuD and were found to be 0.4 microM for ferric aerobactin, 1.0 microM for ferrichrome, 0.3 microM for ferric coprogen, and 5.4 microM for the antibiotic albomycin. Ferrichrome A, ferrioxamine B, and ferrioxamine E, which are poorly taken up via the Fhu system, displayed dissociation constants of 79, 36, and 42 microM, respectively. These are the first estimated dissociation constants reported for a binding protein of a microbial iron transport system. Mutants impaired in the interaction of ferric hydroxamates with FhuD were isolated. One mutated FhuD, with a W-to-L mutation at position 68 [FhuD(W68L)], differed from wild-type FhuD in transport activity in that ferric coprogen supported promotion of growth of the mutant on iron-limited medium, while ferrichrome was nearly inactive. The dissociation constants of ferric hydroxamates were higher for FhuD(W68L) than for wild-type FhuD and lower for ferric coprogen (2.2 microM) than for ferrichrome (156 microM). Another mutated FhuD, FhuD(A150S, P175L), showed a weak response to ferrichrome and albomycin and exhibited dissociation constants two- to threefold higher than that of wild-type FhuD. Interaction of FhuD with the cytoplasmic membrane transport protein FhuB was studied by determining protection of FhuB degradation by trypsin and proteinase K and by cross-linking experiments. His-tag-FhuD and His-tag-FhuD loaded with aerobactin specifically prevented degradation of FhuB and were cross-linked to FhuB. FhuD loaded with substrate and also FhuD free of substrate were able to interact with FhuB.

Base Sequence↗
PubMed2005

Disruption of protein-protein interactions: towards new targets for chemotherapy.

Protein-protein interactions play a key role in various mechanisms of cellular growth and differentiation, and in the replication of pathogen organisms in host cells. Thus, inhibition of these interactions is a promising novel approach for rational drug design against a wide number of cellular and microbial targets. In the past few years, attempts to inhibit protein-protein interactions using antibodies, peptides, and synthetic or natural small molecules have met with varying degrees of success, and these will be the focus of this review.

Animals↗
PubMed2004

Optical lectin based biosensor as tool for bacteria identification.

Biosensor techniques are based on biospecific interaction between the biological parts of biosensor with the analyte. In biosensor construction, antibodies are usually used for the detection of analytes such as microorganism, because of very strong and highly specific interaction. The disadvantages of this assay are a long time needed for antibody isolation and purification as well as difficult regeneration of biosensor chip. The use of lectins instead of antibodies could solve these problems because a several hundred lectins are commercially available and their stability in standard buffers is better compared to monoclonal antibodies. While antibody can only be used to detect that antigen it was designed for, lectin as low affinity molecule may bind several different pathogens. Using the discriminative effect of an artificial neural network the application of a lectin array will compensate for the lower specificity. Microbial surfaces bear many of the sugar residues capable of interacting with lectins. The ability of lectins to react with microbial glycoconjugates means that it is possible to employ them as probes and sorbents for whole cells, mutants and numerous cellular constituents and metabolites, and it makes them useful tools for identification or typing of bacteria. Lectins are attractive reagents for the clinical diagnostic laboratory because of their diverse specificity, commercial availability, a wide range of molecular weights, and their stability in standard buffers. The construction of lectin biosensor could be an advantage method for detection of pathogenic bacteria.

Animals↗
PubMed2006

[Application of modern molecular biology techniques to study micro-ecosystem in the rumen].

The microbial community inhabiting in the rumen is characterized by its high population density, wide diversity and interactive complexity. However, until recently our knowledge of rumen microbiology was primarily based on classical culture based techniques (isolation, enumeration and nutritional characterization) which probably only account for 10% to 20% of the rumen microbial population. Modem molecular biology techniques provide effective methods to study the micro-ecosystem in the rumen. The use of molecular techniques based on nucleic acid probes is likely to revolutionize the approach to microbial ecology in the rumen and provide, not simply a refinement or increased understanding but a complete description of rumen community for the first time. Modem molecular techniques based on sequence comparisons of nucleic acids may be used to explore molecular characterization and provide a classification scheme which predicts natural evolutionary relationships. Genetic fingerprinting techniques that provide a pattern or profile of genetic diversity have been applied in a variety of environmental studies for the analysis of microbial communities. Whole-cell hybridization is a powerful technique which may be used to study the structure and function of microbial communities in situ and describe the expression of key enzymes. Real-time quantitative PCR technique may be conducted to accurately quantify the target microorganisms in the rumen. Development of these procedures and techniques will result in greater insights into community structure and activity of rumen microbial communities in relation to functional interactions, spatial and temporal relationships between different microorganisms and between microorganisms and feed particles. The successful development and application of these methods promise to provide the first opportunity to link distribution and identity of rumen microbes in their natural environment with their genetic potential and in situ activities.

Animals↗