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At least 217 records · Page 12Linked to original sources
PubMed2026

CRISPR/Cas9-mediated knockout of PsLykX gene of pea (Pisum sativum L.) leads to loss of symbiotic nodules.

Pea (Pisum sativum L.) symbiosis with nodule bacteria supplying plants with additional nitrogen is a very specific plant-microbial interaction. Mutual recognition of the partners occurs through perception of bacterial signal molecules (Nod factors) by plant receptors, enabling bacterial entry via root hairs and formation of nitrogen-fixing nodules. The pea gene Sym2, described but not yet cloned, exists in different allelic forms defining the symbiotic specificity, and is therefore thought to encode a Nod factor receptor. The PsLykX gene is a strong candidate for the Sym2, since its alleles coincide with high or low symbiotic specificity; however, to date, no genetic evidence has been obtained for a role of PsLykX in symbiosis. Here, we knocked-out the PsLykX in European pea cultivar Caméor using Agrobacterium-mediated hairy root transformation and CRISPR-Cas9 editing. The roots with editing events confirmed by sequencing lost the ability to form nodules, providing direct functional evidence that PsLykX is essential, at least, for the symbiosis between pea cultivar Caméor and Rhizobium ruizarguesonis RCAM1026.

Pisum sativum↗
PubMed2002

Mechanisms of Emerging Diarrheagenic Escherichia coli Infection.

Diarrheagenic Escherichia coli organisms are major causes of morbidity and mortality worldwide. Although most strains of E. coli are harmless commensals, a few types have emerged that are capable of disrupting the normal physiology of the human gut, producing illness ranging from watery diarrhea to fatal hemorrhagic colitis. Diarrheagenic E. coli cause infection by a variety of complex mechanisms, some of which are incompletely understood. These include adherence, elaboration of toxigenic mediators, invasion of the intestinal mucosa, and transportation of bacterial proteins into the host cells. Specific components of the host-microbial interaction that cause damage have been identified, increasing our understanding of the mechanisms of diarrhea. This article reviews some of the recent findings about the pathogenesis and infectious processes involved in three emerging pathotypes of this fascinating gram-negative bacterium.

Journal Article↗
PubMed1995

Molecular characterization of plasminogen activators in human gingival crevicular fluid.

Plasminogen activators (PAs), a family of serine proteases, and their inhibitors (PAIs) are important in fibrinolysis, wound healing and tissue remodelling. Previous studies revealed differences in the localization of PA activity between healthy and diseased gingival tissues, suggesting that PAs and PAIs could play a part in periodontal homeostasis and disease. PAs and PAIs are synthesized by most of the cells types making up the periodontium and can be identified in gingival crevicular fluid (GCF). These studies sought to characterize the molecular species of PAs and their inhibitors in GCF collected from clinically healthy sites. PA enzymatic activity in GCF samples demonstrated by fibrin zymography revealed the presence of only tissue-type PA (tPA) activity. No urokinase-type PA (uPA) enzymatic activity was detected. tPA enzymatic activity appeared predominantly as an uncomplexed 70-kDa species, although some samples contained enzyme-inhibitor complexes. Quantitation of total tPA by enzyme immunoassay showed a mean concentration of 1.6 ng/microl. Analysis of GCF samples for uPA by immunoblotting and enzyme immunoassay disclosed the presence of small amounts of uPA (0.2 ng/microl), which were present predominantly in activator-inhibitor complexes. Immunoblotting showed specific PAI-2 immunoreactivity bands in high molecular-weight complexes and low molecular-weight degradation products, but less than nanogram amounts of free PAI-2 molecules. Enzyme immunoassay revealed that PAI-2 was present in an at least a seven times greater amount than PAI-1. These observations support the hypothesis that PA-generated proteolysis and its regulation by endogenous inhibitors has a role in the diverse biochemical mechanisms underlying periodontal physiology and pathology including host-microbial interaction, polymorphonuclear leucocyte infiltration, turnover and migration of epithelial cells, connective tissue degradation and remodelling, fibrinolysis and wound healing.

Adult↗
PubMed1981

Epidermoid carcinoma of the gingiva: a possible relationship to PUVA therapy.

A case of squamous cell carcinoma arising in the gingiva of a 30-year-old nonsmoking woman receiving PUVA therapy for vitiligo is reported. There were no typical predisposing factors for oral cancer in the history, other than the latter therapy. Although there are several previous reports of cutaneous carcinoma developing in patients under PUVA therapy, most of such involve development of tumors on skin surfaces exposed to direct ultraviolet radiation either through sunlight or via therapeutic mode.s In this case, there was no direct ultraviolet exposure at the site of carcinoma. We suggest the possibility that, in this case, PUVA may exerted a carcinogenic influence via systemic distribution of ultraviolet-activated psoralens or its metabolites to the gingiva. The possibility of microbial interaction with substances within gingival inflammatory exudate to produce carcinogenic substances is postulated.

Adult↗
PubMed2005

Guts and glory: balancing microbes and the immune response.

Maintaining balance with intestinal flora is an important activity of the immune system in higher metazoans. In this issue of Developmental Cell, Ha et al. demonstrate a central role of a redox balance in microbial interactions in the fruit fly gut.

Animals↗
PubMed2004

The use of bacterial spore formers as probiotics.

The field of probiosis has emerged as a new science with applications in farming and aqaculture as alternatives to antibiotics as well as prophylactics in humans. Probiotics are being developed commercially for both human use, primarily as novel foods or dietary supplements, and in animal feeds for the prevention of gastrointestinal infections, with extensive use in the poultry and aquaculture industries. The impending ban of antibiotics in animal feed, the current concern over the spread of antibiotic resistance genes, the failure to identify new antibiotics and the inherent problems with developing new vaccines make a compelling case for developing alternative prophylactics. Among the large number of probiotic products in use today are bacterial spore formers, mostly of the genus Bacillus. Used primarily in their spore form, these products have been shown to prevent gastrointestinal disorders and the diversity of species used and their applications are astonishing. Understanding the nature of this probiotic effect is complicated, not only because of the complexities of understanding the microbial interactions that occur within the gastrointestinal tract (GIT), but also because Bacillus species are considered allochthonous microorganisms. This review summarizes the commercial applications of Bacillus probiotics. A case will be made that many Bacillus species should not be considered allochthonous microorganisms but, instead, ones that have a bimodal life cycle of growth and sporulation in the environment as well as within the GIT. Specific mechanisms for how Bacillus species can inhibit gastrointestinal infections will be covered, including immunomodulation and the synthesis of antimicrobials. Finally, the safety and licensing issues that affect the use of Bacillus species for commercial development will be summarized, together with evidence showing the growing need to evaluate the safety of individual Bacillus strains as well as species on a case by case by basis.

Animals↗
PubMed2005

Influence of toll-like receptor 4, CD14, tumor necrosis factor, and interleukine-10 gene polymorphisms on clinical outcome in Japanese critically ill patients.

The innate recognition of microbial components and subsequent activation of cytokine network are important in the pathophysiology of sepsis. Recently, functional gene polymorphisms in molecules associated with these responses were demonstrated. On the other hand, it has been claimed that there are ethnic differences in genetic polymorphisms. This study investigated toll-like receptor (TLR) 4, CD14, tumor necrosis factor (TNF)-alpha and -beta, and interleukin (IL)-10 gene polymorphisms in 197 Japanese critically ill patients and 214 healthy control subjects to evaluate the influence of these polymorphisms on clinical outcome. No Japanese participant carrying TLR4Asp299Gly or Thr399Ile was detected. No association of CD14-159C/T polymorphisms with genotype frequency or sepsis mortality was observed. Frequency of TNF-alpha-308 GA genotype was significantly higher in the sepsis group than in the control group and TNF-alpha-308GA and IL-10-592CC genotypes were related to poor outcome of sepsis. Ethnic differences in genetic variations are very important issues and the frequencies in this study differ from those previously reported in Caucasians. In conclusion, this study may indicate that TNF-alpha-308G/A and IL-10-592C/A polymorphisms involved in subsequent activation of cytokine network had a larger effect on clinical outcome in patients with sepsis than TLR4Asp299Gly, Thr399Ile, and CD14-159C/T polymorphisms associated with the initial host-microbial interaction.

APACHE↗
PubMed2006

Co-cultivation of Streptomyces californicus and Stachybotrys chartarum stimulates the production of cytostatic compound(s) with immunotoxic properties.

We have recently shown that the actinobacterium Streptomyces californicus and the fungus Stachybotrys chartarum originating from moisture damaged buildings possess both immunotoxic and immunostimulatory characteristics, which are synergistically potentiated by microbial interaction. In the search for the causative agent(s) behind the immunotoxicity, the cytostatic effects of the co-cultivated spores of S. californicus and S. chartarum were compared to those caused by widely used cytostatic agents produced by streptomycetes. The RAW264.7 macrophages were exposed to four doses of doxorubicin (DOX), actinomycin D (AMD), mitomycin C (MMC) or phleomycin (PHLEO) for 24 h. Kinetics of the spores of the co-cultivated and the separately cultivated microbes (1x10(6) spores/ml) was compared to DOX (0.15 muM). Apoptotic responses were analyzed by measuring DNA content and mitochondria membrane depolarization with flow cytometer, and by the fluorometric caspase-3 assay. The present data indicate that interactions during co-cultivation of S. californicus and S. chartarum stimulate the production of an unidentified cytostatic compound(s) capable of inducing mitochondria mediated apoptosis and cell cycle arrest at S-G(2)/M. The spores of co-cultivated microbes caused a 4-fold collapse of mitochondrial membrane potential and an almost 6-fold caspase-3 activation and DNA fragmentation when compared to control. Similar responses were induced by DNA cleaving compounds, especially DOX and AMD, at the relatively low concentrations, but not the spores of the same microbes when they were grown separately. These data suggest that when growing in the same habitat, interactions between S. californicus and S. chartarum stimulates the production of an unknown cytostatic compound(s) which evoke immunotoxic effects similar to those by chemotherapeutic drugs.

Animals↗
PubMed2006

Modelling the co-occurrence of Streptococcus pneumoniae with other bacterial and viral pathogens in the upper respiratory tract.

Otitis media (OM) is a major burden for all children, particularly for Australian Aboriginal children. Streptococcus pneumoniae, Moraxella catarrhalis, Haemophilus influenzae and viruses (including rhinovirus and adenovirus) are associated with OM. We investigated nasopharyngeal microbial interactions in 435 samples collected from 79 Aboriginal and 570 samples from 88 non-Aboriginal children in Western Australia. We describe a multivariate random effects model appropriate for analysis of longitudinal data, which enables the identification of two independent levels of correlation between pairs of pathogens. At the microbe level, rhinovirus infection was positively correlated with carriage of S. pneumoniae, H. influenzae and M. catarrhalis, and adenovirus with M. catarrhalis. Generally, there were positive associations between bacterial pathogens at both the host and microbe level. Positive viral-bacterial associations at the microbe level support previous findings indicating that viral infection can predispose an individual to bacterial carriage. Viral vaccines may assist in reducing the burden of bacterial disease.

Child, Preschool↗
PubMed2003

Host and microbial constituents influence Helicobacter pylori-induced cancer in a murine model of hypergastrinemia.

BACKGROUND & AIMS: Helicobacter pylori cag(+) strains and high-expression host interleukin 1beta (IL-1beta) polymorphisms augment the risk for intestinal-type gastric adenocarcinoma, a malignancy that predominates in males. We examined the effects of an H. pylori cancer-associated determinant (cagE), IL-1beta, and host gender in a transgenic hypergastrinemic (INS-GAS) murine model of gastric carcinogenesis. METHODS: Male and female INS-GAS mice infected with wild-type H. pylori, an H. pylori cagE(-) mutant, or H. felis were killed 2-24 weeks postchallenge. Gastric injury was scored from 0 to 4, and mucosal IL-1beta levels were quantified by ELISA. RESULTS: Male INS-GAS mice infected with H. pylori uniformly developed atrophy, intestinal metaplasia, and dysplasia by 6 weeks and carcinoma by 24 weeks. Mucosal IL-1beta concentrations increased 12 weeks following Helicobacter challenge, but levels then decreased by 24 weeks. Inactivation of cagE delayed the progression to carcinoma, but neoplasia ultimately developed in all males infected with the H. pylori mutant. In contrast, none of the H. pylori-infected female mice developed cancer, and injury scores, but not IL-1beta levels, were significantly higher in males compared with females. CONCLUSIONS: H. pylori infection induces gastric adenocarcinoma in an experimental mouse model of disease. Cancer is restricted to males and loss of cagE temporally retards but does not abrogate pathologic progression. Mucosal levels of IL-1beta increase prior to the development of gastric cancer but are not related to gender. The INS-GAS model is effective for investigating discrete host-microbial interactions that culminate in gastric cancer within the context of biologic conditions induced by H. pylori.

Adenocarcinoma↗
PubMed2003

Characterization of small bowel resection and intestinal adaptation in germ-free rats.

BACKGROUND: After massive small bowel resection (SBR), the remnant bowel adapts by increasing enterocyte proliferation and apoptosis. The purpose of this study was to investigate the relevance of luminal bacteria on postresection intestinal cell turnover. METHODS: Male germ-free (GF) and normally colonized control rats underwent either a 75% mid-SBR or sham operation. In other experiments, normally colonized control rats were given antibiotics in the drinking water. After 7 days, the remnant ileum was harvested and adaptation verified by alterations in wet weight, crypt depth, and villus height. Proliferation and apoptosis were measured in crypts as the percent of crypt cells staining for Ki-67 or the number of apoptotic bodies per crypt. RESULTS: Both GF and control rats demonstrated significant increases in all adaptive parameters. Proliferation was increased after SBR in both groups, but significantly greater in the GF animals over control. This response could not be recapitulated after antibiotic treatment. Apoptosis increased equally after SBR in all groups. CONCLUSION: Resection-induced intestinal adaptation occurs normally in GF animals. Epithelial-microbial interactions are probably not involved in the activation of enterocyte apoptosis. The germ-free studies offer the possibility that luminal bacteria may attenuate the proliferative response of the enterocyte to massive small bowel resection.

Adaptation, Physiological↗
PubMed1988

The biology of peritonitis and implications for treatment.

Peritonitis continues to be one of the major infectious problems confronting surgeons. Despite the many advances in antimicrobial agents and supportive care, mortality from diffuse suppurative peritonitis remains unacceptably high. The authors review the anatomy and defense capabilities of the peritoneal cavity and then focus on the polymicrobial nature of peritonitis and how, through microbial interactions with host defenses, there is either resolution or persistent infection. They also consider possible infection-potentiating agents in the peritoneal cavity and experimental modes of therapy.

Abdomen, Acute↗
PubMed2003

Artificial mouth model systems and their contribution to caries research: a review.

The complexity of the oral environment, and ethical problems associated with studies of oral diseases in humans inevitably directed the attention to development of laboratory models, that simulate the human oral microcosm. These developments and in particular the in vitro 'artificial mouth' systems have progressed from simple and basic apparatus devised by Magitot and Miller at the end of 19th century to the currently available, highly sophisticated, computer-controlled, multi-station artificial mouth systems. These advances have metamorphosed from the early studies devised primarily to investigate factors affecting the carious process to the present designs that evaluate growth, pathogenicity, metabolism and mineralization of dental plaque under highly controlled conditions. The modern 'artificial mouth systems' can evaluate microbial interactions in simulated dental plaque and similar biofilms and monitor their physical, chemical, biological and molecular features to a very high degree of accuracy. We review and trace here the historical aspects and developments leading to the currently available artificial mouth systems and discuss their contribution to the study of oral flora, especially related to many variants of dental caries.

Biofilms↗
PubMed1998

Rheumatic fever. The relationships between host, microbe, and genetics.

Acute rheumatic fever is a delayed, nonsuppurative sequela of a pharyngeal infection with the group A streptococcus. The onset of the disease is usually characterized by an acute febrile illness; however, there may be chronic involvement of the heart and/or central nervous system. The article explores the relationship between the initial infection and host-microbial interactions that may be operative in disease pathogenesis.

Antigens, Bacterial↗
PubMed1999

Oral flora and pathogenic organisms.

Oral microbial flora consist of numerous bacterial taxa, ranging from aerobes through fastidious anaerobes, and fungi, viruses, and protozoa. Many of these bacteria are unique to the oral cavity. The organisms exist in a complex interrelationship that is regulated and maintained by physical and metabolic microbial interactions, and by environmental factors, such as saliva and diet. Many of these organisms are relatively harmless, although others are significant pathogens, producing local and systemic diseases in healthy and compromised individuals.

Actinomycetaceae↗
PubMed2025

Genome assembly and annotation of the parasitoid jewel wasp Nasonia oneida.

The jewel wasp, Nasonia (Hymenoptera: Pteromalidae), is a well-established model system for evolutionary genetics and host-microbial interactions. Here, we present the genome of N. oneida, a species lacking prior genomic characterization, using 10× Genomics linked-read (400× coverage), Illumina short-read (120× coverage), and transcriptome data (30× coverage). The assembled genome size is 267 Mb, comprising 4,675 scaffolds, with a scaffold N50 of 1 Mb and 98.40% Benchmarking Universal Single-Copy Orthologues (BUSCOs) completeness score. Annotation revealed 32.29% (86.46 Mb) of repetitive sequences and 14,221 protein-coding genes. Comparative genomics of N. oneida with 15 other hymenopteran species validated the presence of 5,939 gene families shared among them, including 3643 single-copy and 2296 multicopy gene families. This study provides the first de novo assembly of N. oneida, providing a significant addition to the growing repertoire of molecular tools for comparative genomics and functional studies to understand the evolution of closely related species as well as the evolution of parasitic wasps.

Animals↗
PubMed2002

Heavy metal speciation in the composting process.

Composting is one of the more efficient and environment friendly methods of solid waste disposal and has many advantages when compared with landfill disposal on which the UK and Ireland are currently heavily dependent. Composting is a very complicated process involving intensive microbial activity and the detailed mechanisms of the process have yet to be fully understood. Metal speciation information can provide an insight into the metal-microbial interaction and would help in the evaluation of the quality of compost. This would facilitate the exploitation of composts in remediation of heavy metal contaminated land. In this work a systematic approach to metal speciation in compost has been taken by applying the three-step method for operationally defined metal speciation of soils and sediments, developed by the European Commission's Standards, Measurement and Testing Programme to monitor the change in metal speciation with time (up to 106 days) for four different waste composting processes. The results have shown that in general metals become less available for the first extraction step as the composting process proceeds. This implies that composting tends to redistribute the metals from more labile forms to more fixed forms which may explain why the application of composts could be useful for with heavy metal contaminated land. There are exceptions to this trend and in some cases, certain metals appear to behave differently depending on the source of the compost.

Bacteria↗
PubMed2003

Host collagen signal induces antigen I/II adhesin and invasin gene expression in oral Streptococcus gordonii.

Microbial interactions with host molecules, and programmed responses to host environmental stimuli, are critical for colonization and initiation of pathogenesis. Bacteria of the genus Streptococcus are primary colonizers of the human mouth. They express multiple cell-surface adhesins that bind salivary components and other oral bacteria and enable the development of polymicrobial biofilms associated with tooth decay and periodontal disease. However, the mechanisms by which streptococci invade dentine to infect the tooth pulp and periapical tissues are poorly understood. Here we show that production of the antigen I/II (AgI/II) family polypeptide adhesin and invasin SspA in Streptococcus gordonii is specifically upregulated in response to a collagen type I signal, minimally the tri-peptide Gly-Pro-Xaa (where Xaa is hydroxyproline or alanine). Increased AgI/II polypeptide expression promotes bacterial adhesion and extended growth of streptococcal cell chains along collagen type I fibrils that are characteristically found within dentinal tubules. These observations define a new model of host matrix signal-induced tissue penetration by bacteria and open the way for novel therapy opportunities for oral invasive diseases.

Adhesins, Bacterial↗