PubMed Health⌕ Search

Biomedical subjects

S Perotto

Publications and source records attributed to S Perotto.

15 recordsLinked to original sources
PubMed2006

Inefficient photosynthesis in the Mediterranean orchid Limodorum abortivum is mirrored by specific association to ectomycorrhizal Russulaceae.

Among European Neottieae, Limodorum abortivum is a common Mediterranean orchid. It forms small populations with a patchy distribution in woodlands, and is characterized by much reduced leaves, suggesting a partial mycoheterotrophy. We have investigated both the photosynthetic abilities of L. abortivum adult plants and the diversity of mycorrhizal fungi in Limodorum plants growing in different environments and plant communities (coniferous and broadleaf forests) over a wide geographical and altitudinal range. Despite the presence of photosynthetic pigments, CO2 fixation was found to be insufficient to compensate for respiration in adult plants. Fungal diversity was assessed by morphological and molecular methods in L. abortivum as well as in the related rare species Limodorum trabutianum and Limodorum brulloi. Phylogenetic analyses of the fungal internal transcribed spacer (ITS) sequences, obtained from root samples of about 80 plants, revealed a tendency to associate predominantly with fungal symbionts of the genus Russula. Based on sequence similarities with known species, most root endophytes could be ascribed to the species complex encompassing Russula delica, Russula chloroides, and Russula brevipes. Few sequences clustered in separate groups nested within Russula, a genus of ectomycorrhizal fungi. The morphotypes of ectomycorrhizal root tips of surrounding trees yielded sequences similar or identical to those obtained from L. abortivum. These results demonstrate that Limodorum species with inefficient photosynthesis specifically associate with ectomycorrhizal fungi, and appear to have adopted a nutrition strategy similar to that known from achlorophyllous orchids.

Carbon Dioxide↗
PubMed2002

Zinc ions alter morphology and chitin deposition in an ericoid fungus.

A sterile mycelium PS IV, an ascomycete capable of establishing ericoid mycorrhizas, was used to investigate how zinc ions affect the cellular mechanisms of fungal growth. A significant reduction of the fungal biomass was observed in the presence of millimolar zinc concentrations; this mirrored conspicuous changes in hyphal morphology which led to apical swellings and increased branching in the subapical parts. Specific probes for fluorescence and electron microscopy localised chitin, the main cell wall polysaccharide, on the inner part of the fungal wall and on septa in control specimens. In Zn-treated mycelium, hyphal walls were thicker and a more intense chitin labelling was detected on the transverse walls. A quantitative assay showed a significant increase in the amount of chitin in metal-treated hyphae.

Acetylglucosamine↗
PubMed2001

Mucoid mutants of the biocontrol strain pseudomonas fluorescens CHA0 show increased ability in biofilm formation on mycorrhizal and nonmycorrhizal carrot roots.

Extracellular polysaccharides play an important role in the formation of bacterial biofilms. We tested the biofilm-forming ability of two mutant strains with increased production of acidic extracellular polysaccharides compared with the wild-type biocontrol strain Pseudomonas fluorescens CHA0. The anchoring of bacteria to axenic nonmycorrhizal and mycorrhizal roots as well as on extraradical mycelium of the arbuscular mycorrhizal fungus Glomus intraradices was investigated. The nonmucoid wild-type strain P. fluorescens CHA0 adhered very little on all surfaces, whereas both mucoid strains formed a dense and patchy bacterial layer on the roots and fungal structures. Increased adhesive properties of plant-growth-promoting bacteria may lead to more stable interactions in mixed inocula and the rhizosphere.

Biofilms↗
PubMed2001

Impact of biocontrol Pseudomonas fluorescens CHA0 and a genetically modified derivative on the diversity of culturable fungi in the cucumber rhizosphere.

Little is known about the effects of Pseudomonas biocontrol inoculants on nontarget rhizosphere fungi. This issue was addressed using the biocontrol agent Pseudomonas fluorescens CHA0-Rif, which produces the antimicrobial polyketides 2,4-diacetylphloroglucinol (Phl) and pyoluteorin (Plt) and protects cucumber from several fungal pathogens, including Pythium spp., as well as the genetically modified derivative CHA0-Rif(pME3424). Strain CHA0-Rif(pME3424) overproduces Phl and Plt and displays improved biocontrol efficacy compared with CHA0-Rif. Cucumber was grown repeatedly in the same soil, which was left uninoculated, was inoculated with CHA0-Rif or CHA0-Rif(pME3424), or was treated with the fungicide metalaxyl (Ridomil). Treatments were applied to soil at the start of each 32-day-long cucumber growth cycle, and their effects on the diversity of the rhizosphere populations of culturable fungi were assessed at the end of the first and fifth cycles. Over 11,000 colonies were studied and assigned to 105 fungal species (plus several sterile morphotypes). The most frequently isolated fungal species (mainly belonging to the genera Paecilomyces, Phialocephala, Fusarium, Gliocladium, Penicillium, Mortierella, Verticillium, Trichoderma, Staphylotrichum, Coniothyrium, Cylindrocarpon, Myrothecium, and Monocillium) were common in the four treatments, and no fungal species was totally suppressed or found exclusively following one particular treatment. However, in each of the two growth cycles studied, significant differences were found between treatments (e.g., between the control and the other treatments and/or between the two inoculation treatments) using discriminant analysis. Despite these differences in the composition and/or relative abundance of species in the fungal community, treatments had no effect on species diversity indices, and species abundance distributions fit the truncated lognormal function in most cases. In addition, the impact of treatments at the 32-day mark of either growth cycle was smaller than the effect of growing cucumber repeatedly in the same soil.

Alanine↗
PubMed2001

Extracellular polysaccharides are involved in the attachment of Azospirillum brasilense and Rhizobium leguminosarum to arbuscular mycorrhizal structures.

Arbuscular mycorrhizal (AM) fungi, one of the most important component of the soil microbial community, establish physical interactions with naturally occurring and genetically modified bacterial biofertilizers and biopesticides, commonly referred to as plant growth-promoting rhizobacteria (PGPR). We have used a genetic approach to investigate the bacterial components possibly involved in the attachment of two PGPR (Azospirillum and Rhizobium) to AM roots and AM fungal structures. Mutants affected in extracellular polysaccharides (EPS) have been tested in in vitro adhesion assays and shown to be strongly impaired in the attachment to both types of surfaces as well as to quartz fibers. Anchoring of rhizobacteria to AM fungal structures may have special ecological and biotechnological significance because it may facilitate colonisation of new rhizospheres by the bacteria, and may be an essential trait for the development of mixed inocula.

Attachment Sites, Microbiological↗
PubMed2000

Ericoid mycorrhizal fungi are common root associates of a Mediterranean ectomycorrhizal plant (Quercus ilex).

Mycorrhiza samples of neighbouring Quercus ilex and Erica arborea plants collected in a postcutting habitat were processed to see whether plants differing in mycorrhizal status harbour the same root endophytes. Three experiments were performed in parallel: (i) isolation, identification and molecular characterization of fungi from surface-sterilized roots of both plant species; (ii) re-inoculation of fungal isolates on axenic E. arborea and Q. ilex seedlings; (iii) direct inoculation of field-collected Q. ilex ectomycorrhizas onto E. arborea seedlings. About 70 and 150 fungal isolates were obtained from roots of Q. ilex and E. arborea, respectively. Among them, Oidiodendron species and five cultural morphotypes of sterile isolates formed typical ericoid mycorrhizas on E. arborea in vitro. Fungi with such mycorrhizal ability were derived from both host plants. Isolates belonging to one of these morphotypes (sd9) also exhibited an unusual pattern of colonization, with an additional extracellular hyphal net. Ericoid mycorrhizas were also readily obtained by direct inoculation of E. arborea seedlings with Q. ilex ectomycorrhizal tips. Polymerase chain-restriction fragment length polymorphism and random amplified polymorphic DNA analyses of the shared sterile morphotypes demonstrate, in the case of sd9, the occurrence of the same genet on the two host plants. These results indicate that ericoid mycorrhizal fungi associate with ectomycorrhizal roots, and the ecological significance of this finding is discussed.

DNA, Ribosomal Spacer↗
PubMed2000

A diverse population of introns in the nuclear ribosomal genes of ericoid mycorrhizal fungi includes elements with sequence similarity to endonuclease-coding genes.

Ericoid mycorrhizal fungi form symbioses with the roots of members of the Ericales. Although only two genera have been identified in culture, the taxonomic diversity of ericoid symbionts is certainly wider. Genetic variation among 40 ericoid fungal isolates was investigated in this study. PCR amplification of the nuclear small-subunit ribosomal DNA (SSU rDNA) and of the internal transcribed spacer (ITS), followed by sequencing, led to the discovery of DNA insertions of various sizes in the SSU rDNA of most isolates. They reached sizes of almost 1,800 bp and occurred in up to five different insertion sites. Their positions and sizes were generally correlated with morphological and ITS-RFLP grouping of the isolates, although some insertions were found to be optional among isolates of the same species, and insertions were not always present in all SSU rDNA repeats within an isolate. Most insertions were identified as typical group I introns, possessing the conserved motifs characteristic of this group. However, other insertions lack these motifs and form a distinct group that includes other fungal ribosomal introns. Alignments with almost 70 additional sequences from fungal nuclear SSU rDNA introns indicate that introns inserted at the same site along the rDNA gene are generally homologous, but they also suggest the possibility of some horizontal transfers. Two of the ericoid fungal introns showed strong homology with a conserved motif found in endonuclease genes from nuclear rDNA introns.

Amino Acid Sequence↗
PubMed2000

Detection and identification of bacterial endosymbionts in arbuscular mycorrhizal fungi belonging to the family Gigasporaceae.

Intracellular bacteria have been found previously in one isolate of the arbuscular mycorrhizal (AM) fungus Gigaspora margarita BEG 34. In this study, we extended our investigation to 11 fungal isolates obtained from different geographic areas and belonging to six different species of the family Gigasporaceae. With the exception of Gigaspora rosea, isolates of all of the AM species harbored bacteria, and their DNA could be PCR amplified with universal bacterial primers. Primers specific for the endosymbiotic bacteria of BEG 34 could also amplify spore DNA from four species. These specific primers were successfully used as probes for in situ hybridization of endobacteria in G. margarita spores. Neighbor-joining analysis of the 16S ribosomal DNA sequences obtained from isolates of Scutellospora persica, Scutellospora castanea, and G. margarita revealed a single, strongly supported branch nested in the genus Burkholderia.

Burkholderia↗
PubMed1994

Lipopolysaccharide epitope expression of Rhizobium bacteroids as revealed by in situ immunolabelling of pea root nodule sections.

To investigate the in situ expression of lipopolysaccharide (LPS) epitopes on nodule bacteria of Rhizobium leguminosarum, monoclonal antibodies recognizing LPS macromolecules were used for immunocytochemical staining of pea nodule tissue. Many LPS epitopes were constitutively expressed, and the corresponding antibodies reacted in nodule sections with bacteria at all stages of tissue infection and cell invasion. Some antibodies, however, recognized epitopes that were only expressed in particular regions of the nodule. Two general patterns of regulated LPS epitope expression could be distinguished on longitudinal sections of nodules. A radial pattern probably reflected the local physiological conditions experienced by endosymbiotic bacteria as a result of oxygen diffusion into the nodule tissue. The other pattern of expression, which followed a linear axis of symmetry along a longitudinal section of the pea nodule, was apparently associated with the differentiation of nodule bacteria and the development of the nitrogen-fixing capacity in bacteroids. Basically similar patterns of LPS epitope expression were observed for pea nodules harboring either of two immunologically distinct strains of R. leguminosarum bv. viciae, although these epitopes were recognized by different sets of strain-specific monoclonal antibodies. Furthermore, LPS epitope expression of rhizobia in pea nodules was compared with that of equivalent strains in nodules of French bean (Phaseolus vulgaris). From these observations, it is suggested that structural modifications of Rhizobium LPS may play an important role in the adaptation of endosymbiotic rhizobia to the surrounding microenvironment.

Antibodies, Bacterial↗
PubMed1994

Bacterial and plant glycoconjugates at the Rhizobium-legume interface.

Many classes of bacterial and plant glycoconjugate have been shown to be involved in establishing the Rhizobium root nodule symbiosis with peas (Pisum sativum). It was demonstrated, using techniques of molecular genetics, that a group of Rhizobium nodulation genes (nod genes) co-operate to synthesize a lipo-oligosaccharide signal molecule that specifically initiates nodule development on legume hosts. An additional gene function, encoded by nodX, has been found to extend the host range of Rhizobium leguminosarum bv. viciae to include nodulation of a pea mutant, cultivar Afghanistan; the nodX gene product specifies the addition of an acetyl group to the terminal N-acetylglucosamine residue at the reducing end of the pentasaccharide core of this signal molecule. Several other classes of bacterial glycoconjugate have also been shown by genetic analysis to be essential for normal nodule development and function: these include a capsular extracellular polysaccharide; lipopolysaccharide in the outer membrane; and cyclic glucans present in the periplasmic space. Potential functions for these glycoconjugates are discussed in the context of tissue and cell invasion by Rhizobium. Some plant components involved in symbiotic interactions have been identified by the analysis of nodule-specific gene expression (early nodulins). Several of the cDNA clones encoding these early nodulins specify proline-rich proteins that presumably correspond to cell wall glycoproteins or membrane arabinogalactan proteins. Other plant glycoconjugates have been identified using monoclonal antibodies as probes. A plant glycoprotein present in intercellular spaces has been identified as a component of the luminal matrix of infection threads. Because it attaches to the surface of bacteria and is itself susceptible to oxidative cross-linking, this glycoprotein may be involved in limiting the progress of microbial infections. Endocytosis of bacteria into the plant cytoplasm is apparently driven by direct interactions between the bacterial surface and the plasma membrane that is exposed within an unwalled infection droplet; glycoprotein and glycolipid components of the plant membrane glycocalyx have been defined using monoclonal antibodies. Differentiation of endosymbiotic bacteroids is preceded by differentiation of the plant-derived peribacteroid membrane which encloses the symbiosome compartment. Using a monoclonal antibody that identifies a group of plant membrane-associated, inositol-containing glycolipids, we have identified a very early marker for the differentiation of peribacteroid membrane from plasma membrane.

Carbohydrate Sequence↗
PubMed1989

Common components of the infection thread matrix and the intercellular space identified by immunocytochemical analysis of pea nodules and uninfected roots.

Three rat hybridoma cell lines have been isolated which produce monoclonal antibodies identifying a noduleenhanced, soluble component of Pisum sativum root nodules. These antibodies each recognized a protease-sensitive band (M(r) 95K) on SDS-polyacrylamide gels. The 95K antigen was resolved by isoelectric focusing into acidic and neutral components which were separately detected by AFRC MAC 236 and MAC 265 respectively. The third antibody (MAC 204) reacted with both acidic and neutral components through an epitope that was sensitive to periodate oxidation. These monoclonal antibodies were used for immunogold localizations at light and electron microscopic levels. In each case, the antigen was shown to be present in the matrix that surrounds the invading rhizobia in infection threads and infection droplets, as well as in the intercellular spaces between plant cell walls of nodules and also of uninfected roots. By contrast, a fourth monoclonal antibody, AFRC JIM 5, labelled a pectic component in the walls of infection threads, and JIM 5 was also found to label the middle lamella of plant cell walls, especially at three-way junctions between cells. The composition and structure of the infection thread lumen is thus comparable to that of an intercellular space.

Journal Article↗
PubMedDate not supplied

Recruiting and retaining phlebotomists.

The phlebotomy team is receiving greater recognition than ever before for its contribution to the service image of the laboratory. Laboratory managers must recognize that phlebotomists are the laboratory's goodwill ambassadors. Because phlebotomists work on the front line, their technical skills and professional demeanor are prime factors in getting physician referrals and attracting patients to the facility. To recruit and retain a skilled professional phlebotomy team, laboratory managers must assess their operations and determine the skills, personal attributes, and education needed to perform the phlebotomy duties. To keep your best employees, try to continually upgrade your training, continuing education, and career advancement opportunities. To learn what makes a successful phlebotomy team, CLMR surveyed several CLMA members to find out how they are recruiting and developing their phlebotomists. Our special thanks go to all our respondents for sharing their expertise and experiences with us.

Blood Specimen Collection↗