Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “SYMBIOSIS”

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 307 records · Page 17Linked to original sources
PubMedDate not supplied

Mass spectrometric analysis of lipo-chitin oligosaccharides--signal molecules mediating the host-specific legume-rhizobium symbiosis.

Lipo-chitin oligosaccharides (LCOs) are novel bacterial glycolipid signal molecules that mediate the species--specific symbiosis between rhizobial bacteria and leguminous plants. Nodulation of the legume roots and nitrogen-fixation in the resulting nodules by Rhizobia is controlled by the bacterial nodulation genes that encode the LCO biosynthetic enzymes. The length of the LCO chitin backbone, the length and degree of unsaturation of the fatty acyl chain attached to it, and the combination of different chemical substituents on the reducing- and nonreducing-terminal residues all contribute to the species--specificity of the signal. LCOs are bioactive in the nanomolar and subnanomolar concentration range and are produced as heterogeneous mixtures, making determination of their structures a difficult task, most successfully approached by the application of modern mass spectrometric methods in combination with specific chemical treatments aimed at identifying specific chemical moieties. This review presents an overview of these methods as they are being used for the structural elucidation of LCOs, and discusses the role of structural diversity in mediating species-specificity.

Carbohydrate Sequence↗
PubMed1994

Symbiosis of biotechnology and biomaterials: applications in tissue engineering of bone and cartilage.

The three ingredients for the successful tissue engineering of bone and cartilage are regulatory signals, cells, and extracellular matrix. Recent advances in cellular and molecular biology of the growth and differentiation factors have set the stage for a symbiosis of biotechnology and biomaterials. Recent advances permit one to enunciate the rules of architecture for tissue engineering of bone and cartilage. The purification and cloning of bone morphogenetic proteins (BMPs) and growth factors such as platelet derived growth factors (PDGF), transforming growth factor-beta (TGF-beta), and insulin-like growth factors (IGF-I) will allow the design of an optimal combination of signals to initiate and promote development of skeletal stem cells into cartilage and bone. Successful and optimal bone and cartilage formation is a synergy of inductive and conductive strategies governed by biomechanics, optimal load bearing, and motion. BMPs function as inductive signals. Biomaterials (both natural and synthetic) mimic the extracellular matrix and play a role in conduction of bone and cartilage. Examples of biomaterials include hydroxyapatite, polyanhydrides, polyphosphoesters, polylactic acid, and polyglycolic acid. The prospects for novel biomaterials are immense, and they likely will be a fertile growth industry. Cooperative ventures between academia and industry and technology transfer from the federal government augur well for an exciting future for clinical applications.

Animals↗
PubMed2001

Specific IgA to lactic acid bacteria in feces of children consuming milk fermented by yoghurt symbiosis and Lactobacillus casei (Danone strain DN 114 001).

An immunoreactive role of lactic acid bacteria established in animals has seldom been investigated in humans. In a large-scale clinical study, children from day-care centers received either yoghurt (Y), milk fermented by yoghurt symbiosis and Lactobacillus casei (DN 114 001) (YC), or gelified milk (GM) as diet supplements during two 30-day supplementation periods separated by one 30-day period without supplementation. Feces samples were collected before, during, and after the 2nd supplementation period. Proteins were extracted in a buffer containing enzymatic inhibitors. IgA levels were assessed and adjusted to the weight of feces samples. Specific IgA to lactic acid bacteria strains (Streptococcus thermophilus 8901A, 8902A; Lactobacillus bulgaricus; Lactobacillus casei) present in Y and YC were assayed in ELISA and adjusted to individual IgA levels. Mean levels of fecal IgA were within reported ranges for pediatric populations of similar age. IgA levels decreased significantly but transiently in children receiving Y, and increased significantly in children receiving GM, but did not vary in the group of children who were given YC. Specific IgA to the 4 strains tested increased significantly during the supplementation period only in the group of children receiving GM, while it was transient and not significant in children receiving YC. No variation was noted in children given Y Specific IgA to lactic acid bacteria can be assayed in feces. Supplementation with fermented milks might induce a mucosal tolerance to environmental flora.

Animals↗
PubMed1992

[Spermatocyte and ovum symbiosis, origin of ontogenesis and phylogenesis of metazoans].

The origin of metazoa implies the passage from an eukarote protozoan to a protozygote ancestor of a metazoan zygote. The most probable hypothesis is that of a symbiotic origin of the first zygote by association of two protists one signifying a spherical oocell and the other a flagellated spermatozoan; this could be the first step of the metazoan ontogenesis and therefore also of the phylogenesis. The genesis can also be explained by two haploid genomes NX NY, three gametes (two spermatozoa and one ovule), NX apparently being able to create both forms, and two zygotes. A double symbiosis, a chromosomic crossing-over and a selective expulsion can prove it.

Animals↗
PubMed2000

The Actinorhizal Symbiosis.

The term "actinorhiza" refers both to the filamentous bacteria Frankia, an actinomycete, and to the root location of nitrogen-fixing nodules. Actinorhizal plants are classified into four subclasses, eight families, and 25 genera comprising more than 220 species. Although ontogenically related to lateral roots, actinorhizal nodules are characterized by differentially expressed genes, supporting the idea of the uniqueness of this new organ. Two pathways for root infection have been described for compatible Frankia interactions: root hair infection or intercellular penetration. Molecular phylogeny groupings of host plants correlate with morphologic and anatomic features of actinorhizal nodules. Four clades of actinorhizal plants have been defined, whereas Frankia bacteria are classified into three major phylogenetic groups. Although the phylogenies of the symbionts are not fully congruent, a close relationship exists between plant and bacterial groups. A model for actinorhizal specificity is proposed that includes different levels or degrees of specificity of host-symbiont interactions, from fully compatible to incompatible. Intermediate, compatible, but delayed or limited interactions are also discussed. Actinorhizal plants undergo feedback regulation of symbiosis involving at least two different and consecutive signals that lead to a mechanism controlling root nodulation. These signals mediate the opening or closing of the window of susceptibility for infection and inhibit infection and nodule development in the growing root, independently of infection mechanism. The requirement for at least two molecular recognition steps in the development of actinorhizal symbioses is discussed.

Journal Article↗
PubMed2006

Dendritic cells interacting mainly with B cells in the lymphoepithelial symbiosis of the human palatine tonsil.

The lymphoepithelial symbiosis (LES) of the human palatine tonsil is composed of spindle- or star-shaped epithelial cells forming a loose meshwork, containing numerous lymphocytes and dendritic cells (DCs). In the present study, we immunohistochemically characterized DCs in the LES (LES-DCs). LES-DCs were phenotypically immature DCs that were S100beta+, fascin-, HLA-DR+, CD1a-, CD80-, CD83-, CD86-, and CD123-. The most characteristic feature of LES-DCs was that they contacted many B cells, which were mostly IgM+ IgD+ resting naive B cells. Langerhans cells (LCs) located in the nonsymbiotic squamous epithelium were immature DCs that were S100beta+, fascin-, and CD1a+ and did not contact lymphocytes. In contrast to LES-DCs, interdigitating dendritic cells (IDCs) in the T zone were mature DCs that were HLA-DR+, CD1a-, fascin+, CD80+, CD83+, and CD86+ and contacted numerous CD4+ T cells. Two subsets of IDC, S100beta+ fascin+ IDC (IDC-1) and S100beta- fascin+ IDC (IDC-2), were identified, and the majority of IDCs are IDC-2. In contrast to IDCs, which were distributed in the T-cell area in groups, LES-DCs were distributed along the crypt as if forming a barrier. These findings suggest that LES-DCs are a novel type of DC playing an important role in the induction of humoral immune response against incoming air- or food-borne pathogenic antigens.

B-Lymphocytes↗
PubMed2004

Nitrogen-fixing symbiosis between photosynthetic bacteria and legumes.

Rhizobia having photosynthetic systems form nitrogen-fixing nodules on the stem and/or root of some species of the legumes Aeschynomene and Lotononis. This review is focused on the recent knowledge about the physiology, genetics and role of the photosystem in these bacteria. Photosynthetic electron transport seems to involve reaction centers, soluble cytochrome c2 and cytochrome bc1. Anaerobically, the electron transport system becomes over-reduced. The photosynthesis genes have been partially characterized; their organization is classical but their regulation is unusual as it is activated by far-red light via a bacteriophytochrome. This original mechanism of regulation seems well adapted to promote photosynthesis during stem symbiosis. Photosynthesis plays a major role in the efficiency of stem nodulation. It is also observed that infrared light stimulates nitrogen fixation in nodules containing photosynthetic bacteroids, suggesting that photosynthesis may additionally provides energy for nitrogen fixation, allowing for more efficient plant growth. Other aspects of these bacteria are discussed, in particular their taxonomic position and nodulation ability, the role of carotenoids and the potential for application of photosynthetic rhizobia in rice culture.

Journal Article↗
PubMed1993

Molecular mechanism of host specificity in legume-rhizobium symbiosis.

Rhizobium - legume symbiosis is a highly specific interaction between the two partners. Host specificity is evident at early stages of infection and results from multiple interactions involving signalling among bacteria and host plants. Host specific plant signals (flavanoids) convert the NodD protein to an active form and its binding with nod box initiates the transcription of inducible nod operons. Common nod genes (nodABC) code for an extracellular mitogenic Nod factor which is required for nodule organogenesis. Host specific genes (hsn) modify the Nod factor to induce root hair deformation on specific hosts. The structure of Nod factor controls host range distinction between species and biovars of rhizobia. Interactions of lectins and Exopolysaccharide/Lipopolysaccharide result in host specific attachment of Rhizobium and its subsequent invasion. Change in Expopolysaccharide structure by the transfer of hsn genes enables the Rhizobium to bind with heterologous host lectins. Conversely, changes in root lectins via gene manipulation enables the heterologous rhizobia to bind and initiate nodulation on heterologous hosts. Finally, host specific signals are required to initiate nitrogen fixation in nodules that are formed.

Journal Article↗
PubMed2004

The IStron CdISt1 of Clostridium difficile: molecular symbiosis of a group I intron and an insertion element.

The IStron CdISt1 was first discovered as an insertion into the tcdA gene of the clinical isolate C34. It combines structural and functional properties of a group I intron at its 5'-end with those of an insertion element at its 3'-end. Up to date four different types could be found, mainly differing in their IS-element portions. Contrasting classical group I introns, CdISt1 is always integrated in ORFs encoding bacterial protein. In case CdISt1 had only the IS-element function such insertion would inactivate the protein encoded by the host gene. It is only due to the self-splicing activity of the group I intron parts that CdISt1 integration does not abolish protein function. Both elements seem to exist in molecular symbiosis and CdISt1 could thus be a prototype of a novel class of genetic elements. Moreover, integration of the CdISt1 into the genome could be advantageous for the bacterium, a motor function for evolution of bacterial proteins is discussed. In clinical practice CdISt1 might well serve as a tool for epidemiological studies of C. difficile infections.

Journal Article↗
PubMed2006

Mycosporine-like amino acids in the zooxanthella-ciliate symbiosis Maristentor dinoferus.

Coral reef organisms living in mutualistic symbioses with phototrophic dinoflagellates are widespread in shallow UV-transparent waters. Maristentor dinoferus is a recently discovered species of marine benthic ciliate that hosts symbiotic dinoflagellates of the genus Symbiodinium. In this study, we tested this ciliate for the occurrence of mycosporine-like amino acids, a family of secondary metabolites that minimize damage from exposure to solar UV radiation by direct screening. Using high-performance liquid chromatography and liquid chromatography coupled to mass spectrometry, five mycosporine-like amino acids (shinorine, palythenic acid, palythine, mycosporine-2-glycine, and porphyra-334) were identified in aqueous methanolic extracts of the symbiosis. This is the first report of mycosporine-like amino acids in a marine ciliate.

Amino Acids↗
PubMed1998

Host cell allometry and regulation of the symbiosis between pea aphids, Acyrthosiphon pisum, and bacteria, Buchnera.

The symbiotic bacteria Buchnera in aphids are borne in cells, called bacteriocytes, in the insect haemocoel. The number and median volume of bacteriocytes in pre-reproductive adult insects varied significantly among 14 parthenogenetic clones of the pea aphid Acyrthosiphon pisum. After logarithmic transformation of the data, the relationship of both number and median volume of bacteriocytes with aphid weight for the clones could be described by common regression lines with slopes significantly greater than zero. The allometric slope for median bacteriocyte volume was calculated as 1.06, by model I regression and 1.94 by model II regression; and the equivalent values of the allometric slope for total volume of bacteriocytes were 1.51 and 2.50, suggesting that the total volume of bacteriocytes increases disproportionately with aphid body weight. The partial correlation coefficient between the number and median volume of bacteriocytes was +0.07, with body weight held constant. It is proposed that the regulation of number and size of bacteriocytes is not linked and that bacteriocytes may not exhibit compensatory changes in size, in response to alteration in number. Experimental manipulation of the rates of bacteriocyte differentiation and division could therefore perturb the total volume of the symbiosis, on which aphid pests depend for normal growth and reproduction.

Journal Article↗
PubMed1995

Symbiosis of nurse and machine through fuzzy logic: improved specificity of a neonatal pulse oximeter alarm.

This article describes the theoretical underpinnings that preceded the design of a new neonatal pulse oximeter alarm that differentiates true from false alarms based on an artificial intelligence theory called "fuzzy logic." The connection between the intuition and sense of advocacy gained through neonatal primary nursing and the application of fuzzy logic to solve the problem of false alarms--that is, the symbiosis between nurse and machine--are explained. Emphasis is placed throughout on the importance of involving nurses in the development of the technology for which they are responsible.

Decision Making↗
PubMed1977

Root hair cell enhancement in tissue cultures from soybean roots: a useful model system: in vitro Rhizobium symbiosis.

A technique for obtaining large numbers of root hair cells in cell cultures from soybeans is described. The cells were grown on agar containing the Prairie Regional Laboratory B5 (PRL-B5) medium for periods longer than 60 days. Mixed populations of cultured root hair cells and cortical cells were used to study the in vitro association between soybean cells and Rhizobium japonicum. The advantages of these types of root cell cultures in studies of symbiosis are discussed.

Journal Article↗
PubMed1978

Regulation by fixed nitrogen of host-symbiont recognition in the Rhizobium-clover symbiosis.

Either NO(3) (-) (16 millimolar) or NH(4) (+) (1 millimolar) completely inhibited infection and nodulation of white clover seedlings (Trifoliin repens) inoculated with Rhizobium trifolii. The binding of R. trifolii to root hairs and the immunologically detectable levels of the plant lectin, trifoliin, on the root hair surface had parallel declining slopes as the concentration of either NO(3) (-) or NH(4) (+) was increased in the rooting medium. This supports the role of trifoliin in binding R. trifolii to clover root hairs. Agglutination of R. trifolii by trifoliin from seeds was not inhibited by these levels of NO(3) (-) or NH(4) (+). The results suggest that these fixed N ions may play important roles in regulating an early recognition process in the Rhizobium-clover symbiosis, namely the accumulation of high numbers of infective R. trifolii cells on clover root hairs.

Journal Article↗
PubMed1984

Host recognition in the Rhizobium-soybean symbiosis: detection of a protein factor in soybean root exudate which is involved in the nodulation process.

The mechanism of host-symbiont recognition in the soybean-Rhizobium symbiosis was investigated utilizing mutants of R. japonicum defective in nodulation. Soybeans were grown in clear plastic growth pouches allowing the identification of the area on the root most susceptible to Rhizobium nodulation; the area between the root tip (RT) and smallest emergent root hair (SERH). The location of nodules in relation to this developing zone is an indication of the rate of nodule initiation. Nodules were scored as to the distance from the RT mark made at the time of inoculation. Seventy-eight per cent of the plants nodulate above the RT mark when inoculated with the wild type R. japonicum strain 3I1b110 with the average distance of the uppermost nodule being approximately 2 millimeters above the RT mark. These data indicate that the wild type strain initiates nodulation rapidly within the RT-SERH zone following inoculation. However, inoculation with the slow-to-nodulate mutant strain HS111 resulted in 100% of the plants nodulating only below the RT mark with the average distance of the uppermost nodule being approximately 56 millimeters below the RT mark. Thus, mutant strain HS111 is defective in the ability to rapidly initiate infection leading to nodulation within the RT-SERH zone. The location of the nodules suggest that stain HS111 must ;adapt' to the root environment before nodulation can occur. To test this, strain HS111 was incubated in soybean root exudate prior to inoculation. In this case, 68% of the plants nodulated above the RT mark with the average distance of the uppermost nodule being approximately 1 millimeter below the RT mark. Experiments indicated that the change in nodule initiation by strain HS111 brought about by incubation in soybean root exudate was due to a phenotypic, rather than a genotypic change. The half-time of root exudate incubation for strain HS111 necessary for optimal nodulation enhancement was less than 6 hours. Heat sensitivity and trypsin sensitivity of the nodulation enhancement factor(s) in soybean root exudate indicate a protein was involved in the reversal of the delay in nodulation by mutant strain HS111.

Journal Article↗
PubMed1991

Nitrogenase Activity and Amounts of Nitrogenase Proteins in a Frankia-Alnus incana Symbiosis Subjected to Darkness.

Effects of prolonged darkness on nitrogenase activity in vivo, nitrogenase activity in vitro, and the amounts of nitrogenase proteins were studied in symbiotic Frankia. Plants of Alnus incana (L.) Moench in symbiosis with a local source of Frankia were grown for 9 to 10 weeks in an 18/6 hour light/darkness cycle. After 12 hours of a light period, the plants were exposed to darkness for up to 40 hours. Nitrogenase activity (acetylene reduction activity) of intact plants was measured repeatedly. Frankia vesicle clusters were prepared from the nodules with an anaerobic homogenization and filtration technique and were used for measurements of in vitro nitrogenase activity and for measurements of the amounts of nitrogenase proteins on Western blots. Antisera made against dinitrogenase reductase (Fe-protein) of Rhodospirillum rubrum and against dinitrogenase (MoFe-protein) of Azotobacter vinelandii were used. Western blots were made transparent and nitrogenase proteins were quantified spectrophotometrically. Nitrogenase activity both in vivo and in vitro decreased after about 23 hours of darkness and continued to decrease to about 25% and 16% of initial activity, respectively, after 40 hours. The amount of Fe-protein and MoFe-protein in Frankia of the same plants decreased to 60% and 35%, respectively, after 40 hours of darkness. Loss of nitrogenase activity thus appeared to be largely explained by loss of MoFe-protein.

Journal Article↗
PubMed1992

The Fifth Thomas James Okey Memorial Lecture: research and practice: the necessary symbiosis.

What relationship should exist between research and practice in the field of addictive behaviour? Are the perspectives essentially independent, or is there a necessary interaction? The extent of productive interaction is considered in three examples; (i) detoxification, (ii) stable abstinence, and (iii) goals other than abstinence. Changes are occurring in the drugs being used, the extents and types of associated co-morbidity, the levels of public and professional concern, and the explanatory paradigms which are dominant; and so it will be increasingly important for both practitioners and researchers to be sensitive and reactive to these changing circumstances. The most productive state for both research and practice will exist when they both feed off, and feed into each other--when there is indeed a necessary symbiosis.

Combined Modality Therapy↗
PubMed1981

Symbiosis and confirmation between the parents of the schizophrenic.

Parents of schizophrenics (N = 17) were compared with parents of nonschizophrenic hospitalized patients (N = 14) and parents of normals (N = 15) on the degree of symbiotic enmeshment and confirmation of individuality in the parental relationship. Symbiosis was divided into six component variables: undifferentiation, dependency, intervention, disapproval of other relationships, separation difficulty, and injunctions. Confirmation was bifurcated into acknowledgment and accommodation. Projective tests (TAT and Make-A-Picture-Story) and interviews were used to measure both variables. The results suggest that mothers of schizophrenics tend to be symbiotically attached to their husbands and view their husbands as forming the same type of attachment to them. Fathers of schizophrenics do not tend to be symbiotically involved with their wives but fail to confirm them. The implications of the results for the family system of the schizophrenic are discussed.

Fathers↗