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At least 199 records · Page 11Linked to original sources

PubMed2005

Bacteriophages--potential for application in wastewater treatment processes.

Bacteriophages are viruses that infect and lyse bacteria. Interest in the ability of phages to control bacterial populations has extended from medical applications into the fields of agriculture, aquaculture and the food industry. Here, the potential application of phage techniques in wastewater treatment systems to improve effluent and sludge emissions into the environment is discussed. Phage-mediated bacterial mortality has the potential to influence treatment performance by controlling the abundance of key functional groups. Phage treatments have the potential to control environmental wastewater process problems such as: foaming in activated sludge plants; sludge dewaterability and digestibility; pathogenic bacteria; and to reduce competition between nuisance bacteria and functionally important microbial populations. Successful application of phage therapy to wastewater treatment does though require a fuller understanding of wastewater microbial community dynamics and interactions. Strategies to counter host specificity and host cell resistance must also be developed, as should safety considerations regarding pathogen emergence through transduction.

Bacteria↗

PubMed1996

Problems and priorities for controlling opportunistic pathogens with new antimicrobial strategies; an overview of current literature.

An International Study Group on New Antimicrobial Strategies (ISGNAS) has been formed in response to the recognition that development of microbial resistance to antibiotics is becoming a serious, world-wide problem. The group met in 1993 for the first time to discuss the feasibility of developing rational alternatives to the use of antibiotics and prepared, as a result, a comprehensive overview of normal (physiological) mechanisms involved in the control of potentially pathogenic (oppotunistic) microorganisms. One objective of ISGNAS is to understand the conditions which allow opportunistic microbes present among the symbionts to cause an infection. There is a need for more coherent information concerning the habitat, growth requirements and host and pathogen properties which allow opportunistic pathogens to cause life-threatening infections. In particular, information is urgently being sought to understand the complexity of the interactions between the vast number of microbial species, and the interactions between the microbes and their host. Another goal is to inspire and enable basic and clinical research that will lead to the development of new therapies for regulating colonization, translocation and infection by opportunistic micro-organisms in patients during periods of decreased resistance. With a sufficient amount of knowledge of how healthy individuals keep opportunistic micro-organisms under control, it may become feasible for physicians to maintain host resistance and inter-microbial factors involved in the containment of opportunistic microbes. Therapies aimed at boostering natural resistance mechanisms will be of critical importance to individuals whose resistance has been compromised as a result of another clinical condition.

Adjuvants, Immunologic↗

PubMed2026

Rumen DNA virome plasticity and viral metabolic potential are associated with seasonal adaptation in grazing yak and cattle on the Qinghai-Tibet Plateau.

BACKGROUND: As a diverse and abundant component of the rumen ecosystem, viruses interact with other microorganisms and are thought to influence microbial metabolism and host productivity. However, how the rumen virome responds to seasonal fluctuations in extreme environments remains poorly understood. Here, metagenomic analyses were used to investigate temporal dynamics of viral diversity, functional potential, and virus-host associations in the rumen virome of yak and cattle on the Qinghai-Tibet Plateau across warm and cold seasons. RESULTS: Rumen viral communities exhibited pronounced seasonal variation in both yaks and cattle, with higher alpha diversity observed during the cold season than in the warm season. Across seasons, the yak rumen virome showed greater alpha diversity and community stability than that of cattle. In total, 27,353 temperate and 31,976 virulent viral operational taxonomic units (vOTUs) were identified, predominantly belonging to the class Caudoviricetes. These viruses were linked to microbial hosts spanning 24 bacterial and 8 archaeal phyla, with Bacteroidota and Bacillota representing the dominant lineages. Virus-host associations were more numerous in the cold season and showed distinct host-specific patterns between yaks and cattle. Cold-season virome exhibited reduced diversity of anti-defense genes and enrichment of auxiliary metabolic genes (AMGs) associated with fatty acid metabolism and hemicellulose degradation. Notably, greater divergence between yaks and cattle was observed during the cold season: the yak rumen virome was enriched in pathways related to amino acid, lipid, and energy metabolism, as well as cellulose-degrading CAZyme families, whereas the cattle rumen virome showed enrichment in general carbohydrate metabolism and replication and repair processes. CONCLUSION: Seasonal plasticity of rumen DNA virome and pronounced interspecific divergence between yaks and cattle provide insight into their distinct microbial processes in the harsh environment of the Qinghai-Tibet Plateau. These findings suggest that the rumen DNA virome exhibits complex ecological and functional responses to seasonal variation and may be associated with host-microbiome interactions and nutrient utilization under environmental stress. This study highlights the ecological relevance of rumen viral genomes in understanding virus-microbiome interactions, microbial adaptation, and nutrient utilization in high-altitude ruminants.

Auxiliary metabolic genes↗

PubMed2001

Microbial interactions and biocontrol in the rhizosphere.

The loss of organic material from the roots provides the energy for the development of active microbial populations in the rhizosphere around the root. Generally, saproptrophs or biotrophs such as mycorrhizal fungi grow in the rhizosphere in response to this carbon loss, but plant pathogens may also develop and infect a susceptible host, resulting in disease. This review examines the microbial interactions that can take place in the rhizosphere and that are involved in biological disease control. The interactions of bacteria used as biocontrol agents of bacterial and fungal plant pathogens, and fungi used as biocontrol agents of protozoan, bacterial and fungal plant pathogens are considered. Whenever possible, modes of action involved in each type of interaction are assessed with particular emphasis on antibiosis, competition, parasitism, and induced resistance. The significance of plant growth promotion and rhizosphere competence in biocontrol is also considered. Multiple microbial interactions involving bacteria and fungi in the rhizosphere are shown to provide enhanced biocontrol in many cases in comparison with biocontrol agents used singly. The extreme complexity of interactions that can occur in the rhizosphere is highlighted and some potential areas for future research in this area are discussed briefly.

Bacteria↗

PubMed1999

IL-6 levels in gingival crevicular fluid (GCF) from patients with non-insulin dependent diabetes mellitus (NIDDM), adult periodontitis and healthy subjects.

Cytokines play an important role in the pathology associated with chronic inflammatory diseases. One of these cytokines, interleukin 6 (IL-6) is a major mediator of the host response to tissue injury, infection and bone resorption. In the present study, gingival crevicular fluid (GCF) level of IL-6 was determined in patients with non-insulin dependent diabetes mellitus (NIDDM) with periodontitis, adult periodontitis, and healthy controls by use of an enzyme linked immunosorbent assay (ELISA). Twenty-four NIDDM patients with periodontitis, twenty-four adult periodontitis and twenty-four healthy controls were selected for the study. GCF sampling was performed on the vestibular aspects of maxillary incisors and canine teeth. Plaque index (PI), gingival index (GI), gingival bleeding time index (GBTI), probing depth (PD) and probing attachment levels (PAL) were recorded from each sampling area and also the entire dentition. NIDDM and adult periodontitis patients had numerous sites with radiographic evidence of alveolar bone resorption, loss of attachment and pocket depth greater than 3 mm. The mean GCF IL-6 level was 2.43 +/- 0.97 ng/ml in NIDDM patients, 1.31 +/- 0.92 ng/ml in adult periodontitis and 0.62 +/- 0.58 ng/ml in healthy subjects, respectively (p < 0.05). GCF IL-6 levels were markedly higher in NIDDM and adult periodontitis groups compared to the healthy controls. No correlation was found between GCF IL-6 levels and all clinical parameters. These findings suggested that GCF IL-6 levels were significantly higher in the area of inflammation and periodontal destruction locally. The high IL-6 levels in NIDDM patients might be due to different microbial flora in periodontal pockets and altered immune system. Future studies are needed to evaluate the complex interaction among IL-6 GCF levels, host response and local microbial environment in the NIDDM patients.

Adolescent↗

PubMed2005

Toward a genome-wide systems biology analysis of host-pathogen interactions in group A Streptococcus.

Genome-wide analysis of microbial pathogens and molecular pathogenesis processes has become an area of considerable activity in the last 5 years. These studies have been made possible by several advances, including completion of the human genome sequence, publication of genome sequences for many human pathogens, development of microarray technology and high-throughput proteomics, and maturation of bioinformatics. Despite these advances, relatively little effort has been expended in the bacterial pathogenesis arena to develop and use integrated research platforms in a systems biology approach to enhance our understanding of disease processes. This review discusses progress made in exploiting an integrated genome-wide research platform to gain new knowledge about how the human bacterial pathogen group A Streptococcus causes disease. Results of these studies have provided many new avenues for basic pathogenesis research and translational research focused on development of an efficacious human vaccine and novel therapeutics. One goal in summarizing this line of study is to bring exciting new findings to the attention of the investigative pathology community. In addition, we hope the review will stimulate investigators to consider using analogous approaches for analysis of the molecular pathogenesis of other microbes.

Computational Biology↗

PubMed1992

Microbial interaction with animal cell surface carbohydrates.

Microbes have selected primarily carbohydrates for attachment to host animal cells. Recent studies have revealed essential characteristics in the recognition of receptor carbohydrates. Of importance is the property of recognizing also sequences placed inside an oligosaccharide chain, which differs from most animal antibodies. This is the basis for series of isoreceptors with the minimum receptor sequence in common but with separate neighbouring groups. There are families of microbial ligands that show different preferences for members within one series of isoreceptors, indicating only slight differences in the complementary binding sites of the proteins. Such differences may explain shifts in the selectivity of separate host tissues for infection. A second characteristic is the low affinity interaction often found where simple receptor-containing saccharides are unable to inhibit attachment. Technical possibilities are rapidly developing for the design of synthetic receptor analogues to be used in the therapy of clinical infections. This is urgently needed in cases where no rational therapy exists today.

Adhesins, Escherichia coli↗

PubMed2003

Microbial globins.

Globins are an ancient and diverse superfamily of proteins. The globins of microorganisms were relatively ignored for many decades after their discovery by Warburg in the 1930s and rediscovery by Keilin in the 1950s. The relatively recent focus on them has been fuelled by recognition of their structural diversity and fine-tuning to fulfill (probably) discrete functions but particularly by the finding that a major role of certain globins is in protection from the stresses caused by exposure to nitric oxide (NO)--itself a molecule that has attracted intense curiosity recently. At least three classes of microbial globin are recognised, all having features of the classical globin protein fold. The first class is typified by the myoglobin-like haemprotein Vgb from the bacterium Vitreoscilla, which has attracted considerable attention because of its ability to improve growth and metabolism for biotechnological gain in a variety of host cells, even though its physiological function is not fully understood. The truncated globins are widely distributed in bacteria, microbial eukaryotes as well as plants and are characterised by being 20-40 residues shorter than Vgb. The polypeptide is folded into a two-over-two helical structure while retaining the essential features of the globin superfamily. Roles in oxygen and NO metabolism have been proposed. The third and best understood class comprises the flavohaemoglobins, which were first discovered and partly characterised in yeast. These are distinguished by the presence of an additional domain with binding sites for FAD and NAD(P)H. Widely distributed in bacteria, these proteins undoubtedly confer protection from NO and nitrosative stresses, probably by direct consumption of NO. However, a bewildering array of enzymatic capabilities and the presence of an active site in the haem pocket reminiscent of peroxidases hint at other functions. A full understanding of microbial globins promises advances in controlling the interactions of pathogenic bacteria with their animal and plant hosts, and manipulations of microbial oxygen transfer with biotechnological applications.

Amino Acid Sequence↗

PubMed2006

A p67Phox-like regulator is recruited to control hyphal branching in a fungal-grass mutualistic symbiosis.

Key requirements for microbes to initiate and establish mutualistic symbiotic interactions with plants are evasion of potential host defense responses and strict control of microbial growth. Reactive oxygen species (ROS) produced by a specific NADPH oxidase isoform, NoxA, regulate hyphal growth in the mutualistic interaction between the fungal endophyte Epichloë festucae and its grass host Lolium perenne. Unlike mammalian systems, little is known about the fungal NADPH oxidase complex and its response to differentiation signals. We identify an E. festucae p67(phox)-like regulator, NoxR, dispensable in culture but essential in planta for the symbiotic interaction. Plants infected with a noxR deletion mutant show severe stunting and premature senescence, whereas hyphae in the meristematic tissues show increased branching leading to increased fungal colonization of pseudostem and leaf blade tissue. Inhibition of ROS production or overexpression of noxR recapitulates the hyperbranching phenotype in culture. NoxR interacts in vitro with the small GTP binding protein RacA and requires a functional RacA binding site to complement the noxR mutant and restore the wild-type plant interaction phenotype. These results show that NoxR is a key regulator of NoxA in symbiosis, where it acts together with RacA to spatially regulate ROS production and control hyphal branching and patterning.

Amino Acid Sequence↗

PubMed2005

B cell superantigens: a microbe's answer to innate-like B cells and natural antibodies.

Marginal zone B cells and B-1 cells have been termed innate-like B cells as they express limited repertoires that play special roles in immune defenses against common infections. These B cells are the sources of natural antibodies and are capable of highly accelerated clonal responses that help counter blood-borne infections. We have characterized a class of microbial product with highly adapted binding interactions with host immunoglobulins/B cell receptors (BCRs), which enable the targeting of large supra-clonal sets of B cells for activation-associated apoptotic death. In recent studies, we have shown that all B cells with V region-targeted BCRs are susceptible. However, compared to follicular B cells, in vivo exposure preferentially causes innate-like B cells to undergo induced death with subsequent long-lasting supra-clonal depletion and immune tolerance. Based on these properties, it is likely that B cell superantigens influence the pathogenesis of some common infections, but also may provide novel therapeutic opportunities to treat B cell neoplastic and autoimmune diseases.

Animals↗

PubMed1993

Iron acquisition in microbial pathogenesis.

Successful competition for iron by potential pathogens is essential to establish infection. The roles of the various types of microbial iron acquisition systems in host-pathogen interactions depend on the nature of the infection and the location of the pathogen within the host. Microbes infecting the extracellular spaces of the host employ different strategies for iron acquisition than those that invade and multiply within host cells.

Animals↗

PubMed2003

Multifaceted functions of B cells in chronic hepatitis C virus infection.

Hepatitis C virus (HCV) elicits T- and B-cell responses which are believed to play an important role in infection control. B cells have generally been neglected because they do not seem to significantly influence the course of HCV infection. In this review, B lymphocytes are viewed both as classical antibody producing cells, with the hypervariable region 1 being a biologically relevant target protein and as a model of virus-host interaction in lymphoproliferative disorders characteristic of persistent microbial infections.

B-Lymphocytes↗

PubMed2002

Chemical ecology of marine microbial defense.

Because marine animals and plants are continuously exposed to a large diversity of potentially harmful microorganisms, it seems reasonable to hypothesize that potential hosts might produce bioactive compounds to deter microbial attack. However, little is known about how host metabolites may defend against harmful microbes or facilitate the growth or colonization of helpful symbionts. While there is a large body of literature describing the antimicrobial activities of marine secondary metabolites, we are only now beginning to understand how these compounds function in an ecological context. For example, there is mounting evidence that nontoxic concentrations of secondary metabolites can have significant effects on microbial behavior, suggesting that certain host-microbe interactions are chemically mediated. Herein, we discuss the importance of employing ecologically relevant assays to elucidate microbiological effects and the need to develop a better understanding of host-microbe associations within an ecologically realistic context. Continued research in this field along with improved techniques will certainly provide further insight into how microbes have influenced the evolution of secondary metabolite production in marine organisms.

Animal Population Groups↗

PubMed1992

Emerging strategies for enhancing crop resistance to microbial pathogens.

There are marked differences in the pattern of host gene expression in incompatible plant:microbial pathogen interactions compared with compatible interactions, associated with the elaboration of inducible defenses. Constitutive expression of genes encoding a chitinase or a ribosome-inactivating protein in transgenic plants confers partial protection against fungal attack, and a large repertoire of such antimicrobial genes has been identified for further manipulation. In addition, strategies are emerging for the manipulation of multigenic defenses such as lignin deposition and synthesis of phytoalexin antibiotics by overexpression of genes encoding rate determining steps, modification of transcription factors or other regulatory genes, and engineering production of novel phytoalexins by interspecies transfer of biosynthetic genes. The imminent cloning of disease resistance genes, further molecular dissection of stress signal perception and transduction mechanisms, and identification of genes that affect symptom development will provide attractive new opportunities for enhancing crop protection. Combinatorial integration of these novel strategies into ongoing breeding programs should make an important contribution to effective, durable field resistance.

Amino Acid Sequence↗

PubMed2026

Friends or foes: Unraveling the tsetse fly-Spiroplasma symbiosis.

Tsetse flies (Glossina spp.) transmit African trypanosomes, the causative agents of human African and African animal trypanosomiases (HAT and AAT, respectively). These neglected tropical diseases impose significant public health and economic burdens across sub-Saharan Africa. Trypanosome transmission by tsetse flies is influenced by multiple factors, including host genetic background, ecological factors, and interactions with heritable microbial endosymbionts. Spiroplasma glossinidia has recently emerged as an important modulator of tsetse reproductive fitness and vector competence, making it a potential target for symbiont-based vector control strategies. In this review, we summarize the current knowledge of the tsetse-Spiroplasma symbiosis. We detail Spiroplasma's spatial and temporal infection dynamics in laboratory-reared and natural populations. Additionally, we highlight key aspects of the bacterium's genomics, phylogenetics, and physiological interactions with its tsetse host, including influences on host gene expression reproductive physiology, and vector competence. Finally, we discuss how the tsetse-Spiroplasma symbiosis could be harnessed to develop innovative, biological-based vector control and trypanosome transmission-blocking strategies, and we identify critical gaps that must be addressed to translate these findings into effective disease control interventions.

Animals↗

PubMed2004

Microbial-gut interactions in health and disease. Epithelial cell responses.

Intestinal epithelial cells are unique in that they represent the only host cells that are constantly interacting with a very large bacterial population in the lumen. The single monolayer of epithelial cells consists of subpopulations with distinct functions that include protection against luminal microorganisms. Although the microbial flora remains to be fully characterized, its normal relationship with the host intestinal epithelial cells appears to be predominantly symbiotic or commensal. The molecular complexity of the epithelial-microbial relationship has been shown in studies that have examined the establishment of the resident bacteria in germ-free mice. Recent work has also demonstrated the ability of resident bacteria to enhance epithelial protective responses. The mechanisms by which epithelial cells may avoid pro-inflammatory responses to resident microorganisms, while retaining the capacity to respond to pathogens, are also being characterized.

Enterobacteriaceae↗

PubMed2004

Microbes and their products--physiological effects upon mammalian mucosa.

A dynamic array of interactions occurs between pathogens and host mucosal surfaces. The signature molecules unique to microbial pathogens allow the mammalian immune system to recognize them as non-self. This recognition, mediated by the toll-like receptor proteins, results in innate immune responses targeted against the invading organism. Pathogens also elaborate a variety of proteins that actively engage host signaling pathways and subvert them to facilitate their growth and dispersal. These interactions, developed over a long evolutionary period, have been specialized to exquisite detail. These proteins and toxins are either secreted into the medium or directly delivered into host cells by specialized secretion systems. An array of host function alterations is mediated by microbial pathogens including inflammatory responses, secretory responses, alteration of host cytoskeleton, disruption of epithelial tight junctions and apoptosis. The signaling axes involved in these interactions are potential targets for therapeutic strategies against infectious microbes.

Animals↗

PubMed2006

Bacteriophage migration via nematode vectors: host-parasite-consumer interactions in laboratory microcosms.

Pathogens vectored by nematodes pose serious agricultural, economic, and health threats; however, little is known of the ecological and evolutionary aspects of pathogen transmission by nematodes. Here we describe a novel model system with two trophic levels, bacteriophages and nematodes, each of which competes for bacteria. We demonstrate for the first time that nematodes are capable of transmitting phages between spatially distinct patches of bacteria. This model system has considerable advantages, including the ease of maintenance and manipulation at the laboratory bench, the ability to observe many generations in short periods, and the capacity to freeze evolved strains for later comparison to their ancestors. More generally, experimental studies of complex multispecies interactions, host-pathogen coevolution, disease dynamics, and the evolution of virulence may benefit from this model system because current models (e.g., chickens, mosquitoes, and malaria parasites) are costly to maintain, are difficult to manipulate, and require considerable space. Our initial explorations centered on independently assessing the impacts of nematode, bacterium, and phage population densities on virus migration between host patches. Our results indicated that virus transmission increases with worm density and host bacterial abundance; however, transmission decreases with initial phage abundance, perhaps because viruses eliminate available hosts before migration can occur. We discuss the microbial growth dynamics that underlie these results, suggest mechanistic explanations for nematode transmission of phages, and propose intriguing possibilities for future research.

Animals↗