Search

Your search keyword '"Eleftherios Chalkiadakis"' showing total 3 results
Start Over Author "Eleftherios Chalkiadakis" Search Limiters Available in Library Collection
3 results on '"Eleftherios Chalkiadakis"'

1. The cepacian-like exopolysaccharide of Paraburkholderia ultramafica STM10279T enhances growth and metal adaptation of Tetraria comosa on New Caledonian ultramafic soil

Author

Alexandre Bourles, Guillaume Pierre, Hamid Amir, Alizée Le Floc’h, Eleftherios Chalkiadakis, Valérie Médevielle, Philippe Jourand, Philippe Michaud, Valérie Burtet-Sarramégna, and Linda Guentas

Subjects
PGPR, exopolysaccharides, biostimulant, Paraburkholderia, plant metal alleviation, ultramafic soil, Plant culture, SB1-1110
Abstract

Paraburkholderia ultramafica STM10279T is a metal-tolerant rhizobacterium that promotes plant growth. It was isolated from the roots of Tetraria arundinaceae, a pioneer endemic tropical herb growing on ultramafic soils in New Caledonia. We have recently shown that the main mechanism of metal tolerance of P. ultramafica is related to the production of an acidic exopolysaccharide (EPS). To explore the potential role of this EPS in the plant’s environmental adaptation, we first elucidated its structure by employing a combination of chromatography and mass spectrometry techniques. These analyses revealed that the EPS is highly branched and composed of galactosyl (35.8%), glucosyl (33.2%), rhamnosyl (19.5%), mannosyl (7.2%), and glucuronosyl residues (4.4%), similar to the EPS of the Burkholderia cepacia complex known as cepacian. We subsequently conducted greenhouse experiments on Tetraria comosa plantlets inoculated with P. ultramafica or a solution of its EPS during transplanting onto ultramafic substrate. The data showed that the dry weight of T. comosa shoots was 2.5 times higher in the plants treated with the EPS compared to the unexposed plants. In addition, inductively coupled plasma–optical emission spectrometry (ICP-OES) analysis revealed that exposure to the EPS significantly increased Ca, Mg, K, and P uptake as well as K content in roots. In vitro experiments using the Pikovskaya method showed that the EPS was able to solubilize phosphorus. Consistent with the retention of metals in roots and a reduction in shoots, our data revealed a significant decrease in metal translocation factors (TFs) in the plants inoculated with the EPS. These results suggest a beneficial effect of the rhizobacterial EPS on plant growth and abiotic stress mitigation. In addition, the data suggest that the reduced levels of trace metals in plants exposed to P. ultramafica STM10279T are due to metal chelation by the EPS. Further investigations are needed to firmly demonstrate whether this EPS could be used as a biostimulant for plant growth and adaptation to ultramafic soils.

Published
2024
Full Text
View/download PDF

2. New Caledonian ultramafic conditions structure the features of Curtobacterium citreum strains that play a role in plant adaptation

Author

Farid Juillot, Clarisse Majorel, Eleftherios Chalkiadakis, Valérie Medevielle, Alexandre Bourles, Hamid Amir, Valérie Burtet-Sarramegna, Philippe Jourand, Linda Guentas, and Yvon Cavaloc

Subjects
0303 health sciences, Rhizosphere, Pioneer species, metal tolerance, 030306 microbiology, ultramafic soils, Immunology, Curtobacterium citreum, General Medicine, Biology, biology.organism_classification, Applied Microbiology and Biotechnology, Microbiology, 03 medical and health sciences, plant metal alleviation, Ultramafic rock, Botany, Genetics, exopolysaccharide, Adaptation, Molecular Biology, Curtobacterium, 030304 developmental biology
Abstract

The present study focused on the characterization of 10 Curtobacterium citreum strains isolated from the rhizosphere of pioneer plants growing on ultramafic soils from New Caledonia. Taxonomic status was investigated using a polyphasic approach. Three strains (BE, BB, and AM) were selected in terms of multiple-metal resistance and plant-growth-promoting traits. They were tested on sorghum growing on ultramafic soil and compared with the reference strain C. citreum DSM20528T. To better understand the bacterial mechanisms involved, biosorption, bioaccumulation, and biofilm formation were investigated for the representative strain of the ultramafic cluster (strain BE) versus C. citreum DSM20528T. The polyphasic approach confirmed that all native isolates belong to the same cluster and are C. citreum. The inoculation of sorghum with strains BE and BB significantly reduced Ni content in shoots compared with inoculation with C. citreum DSM20528T and control values. This result was related to the higher Ni tolerance of the ultramafic strains compared with C. citreum DSM20528T. Ni biosorption and bioaccumulation showed that BE exhibited a lower Ni content, which is explained by the ability of this strain to produce exopolysaccharides involved in Ni chelation. We suggested that ultramafic C. citreum strains are more adapted to this substrate than is C. citreum DSM20528T, and their features allow them to enhance plant metal tolerance.

Published
2019

3. Isolation and partial characterization of bacteria (Pseudoalteromonas sp.) with potential antibacterial activity from a marine costal environment from New Caledonia

Author

Véronique Kerjean, Suzanne Chanteau, Elise Petit, Eleftherios Chalkiadakis, Eric Deslandes, Myrielle Dupont-Rouzeyrol, Marilyne Fauchon, Jean Guezennec, Rémi Dufourcq, Dengue et Arbovirose (URE-DA), Institut Pasteur de Nouvelle-Calédonie, Réseau International des Instituts Pasteur (RIIP)-Réseau International des Instituts Pasteur (RIIP), Plateforme technologique BIODIMAR, Université de Brest (UBO), and Ministère de l'Outre-Mer

Subjects
Geologic Sediments, medicine.disease_cause, Applied Microbiology and Biotechnology, Marine bacteriophage, Pseudoalteromonas, antibacterial activity, MESH: Staphylococcus aureus, MESH: Ecosystem, characterization, MESH: Phylogeny, Phylogeny, MESH: Microbial Sensitivity Tests, 0303 health sciences, biology, MESH: Escherichia coli, Antimicrobial, Anti-Bacterial Agents, marine bacteria, MESH: Pseudomonas aeruginosa, Pseudomonas aeruginosa, MESH: Enterococcus, Antibacterial activity, Staphylococcus aureus, Microbial Sensitivity Tests, Enterococcus faecalis, Microbiology, 03 medical and health sciences, Antibiotic resistance, New Caledonia, MESH: Anti-Bacterial Agents, Antibiosis, medicine, Escherichia coli, [SDV.BBM]Life Sciences [q-bio]/Biochemistry, Molecular Biology, Seawater, 14. Life underwater, Ecosystem, MESH: Antibiosis, 030304 developmental biology, 030306 microbiology, MESH: Pseudoalteromonas, screening, MESH: Seawater, MESH: Geologic Sediments, MESH: New Caledonia, biology.organism_classification, Bacteria, Enterococcus
Abstract

Marine bacteria are a rich source of bioactive metabolites. However, the microbial diversity of marine ecosystem still needs to be explored. The aim of this study was to isolate and characterize bacteria with antimicrobial activities from various marine coastal environment of New Caledonia. We obtained 493 marine isolates from various environments and samples of which 63 (12·8%) presented an antibacterial activity against a panel of reference pathogenic strains (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Enterococcus faecalis). Ten out of the most promising strains were cultured, fractionated and screened for antibacterial activity. Four of them (NC282, NC412, NC272 and NC120) showed at least an activity against reference and multidrug-resistant pathogenic strains and were found to belong to the genus Pseudoalteromonas, according to the 16S phylogenetic analysis. The NC282 strain does not belong to any described Pseudoalteromonas species and might be of interest for further chemical and biological characterization. These findings suggest that the identified strains may contribute to the discovery for new sources of antimicrobial substances to develop new therapies to treat infections caused by multidrug-resistant bacteria. Significance and Impact of the Study With the constant increasing of bacterial resistance against known antibiotics in worldwide public health, it is now necessary to find new sources of antimicrobials. Marine bacteria from New Caledonia were isolated, tested for antibacterial activity and characterized to find new active molecules against multidrug-resistant bacteria. This study illustrates the diversity of the marine ecosystem with potent new bacteria species. Also the potential of marine bacteria as a rich source of bioactive molecule, for example antibiotics, is highlighted.

Published
2014
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results