Bacterial siderophores promote plant growth: Screening of catechol and hydroxamate siderophores

The aim of the study was to determine the quality and quantity of siderophores produced by bacteria isolated from plants' roots. The second aim was to determine the effect of siderophores on plants growth (Festuca rubra L. and Brassica napus L.). The study was carried out using bacteria isolated from roots of: Arabidopsis thaliana L., F. rubra, and Agrostis capillaris L., growing on the heavy metals contaminated area. The chrome azurol sulfonate (CAS) test, Arnow's test for catechol siderophores, and Csaksy's test for hydroxamate siderophores were performed. Among the bacteria, 42 isolates (39%) had a positive result in the CAS. Endophytic bacteria were mostly producing the catechol siderophores. It was found that F. rubra is the plant which is linked with the highest number of siderophores producing bacteria. The highest concentration of siderophores was noted for ectorhizospheric bacteria associated with A. thaliana, hyperaccumulating plant. It was found that hydroxamate siderophores are mainly produced by ectorhizosphere and rhizoplane bacteria. The siderophores producing bacteria reduced the toxicity of metals and improved the phytoremediation. Siderophores treatment increased the growth of plants in the biological assay, growing on two different soils: one highly contaminated with heavy metals and the second strongly alkaline soil.     

The neuroendocrine phenotype,cellular plasticity,and the search for genetic switches: redefining the diffuse neuroendocrine system

The term neuroendocrine has been used to define cells that secrete their products in a regulated manner, in response to a specific stimulus. The neuroendocrine system includes neurons and endocrine cells sharing a common phenotypic program characterized by the expression of markers such as neuropeptides, chromogranins, neuropeptide processing enzymes SPC2 and SPC3 (subtilase-like pro-protein convertases) or dense core secretory granules. Various theories such as the APUD (amine precursor uptake decarboxylation) concept, the diffuse neuroendocrine system (DNES) or the paraneuron concept have been put forth to classify neuroendocrine cells as a cohesive group. Neuroendocrine characteristics have been used as evidence of a common embryological origin for normal and neoplastic cells. However, it is now recognized that neuroendocrine characteristics can be observed in various cell types, such as immunocytes, that are not of a common embryological origin with either neurons or endocrine cells. We propose to redefine previous "neuroendocrine" concepts to include the notion that activation of specific genetic switches can lead to the expression of a partial or full neuroendocrine phenotype in a variety of cell types, including immune cells.     

The Bordetella type III secretion system: its application to vaccine development

B. pertussis is a causative agent of whooping cough (pertussis) in humans. Despite wide-scale vaccination in many countries, there is serious concern about pertussis as a re-emerging disease. Re-emergence of pertussis may be explained by several factors: the short duration of protection by the currently available acellular pertussis vaccine, an increase in asymptomatic adult carriers and expansion of strains with certain antigenic variations which are not covered by currently available vaccines. To develop safer and more efficacious vaccines which confer more prolonged protection, researchers are focusing on identification and characterization of new virulence factors. One candidate for protective antigens is the type III secretion system and its secreted proteins.     

Electron spin resonance--spin stabilization in enzymatic systems: detection of semiquinones produced during peroxidatic oxidation of catechols and catecholamines

The electron spin resonance-spin stabilization technique has been applied in an enzymatic system. This technique, which generates radicals in high steady-state concentration under static conditions, involves the use of limited quantities of enzyme and substrate while allowing facile spectral interpretation. In this work $\text{o}$-semiquinone intermediates produced during peroxidase-catalyzed oxidation of catechols and catecholamines have been detected as their metal complexes with Zn²⁺. No significant effect on the peroxidase activity was found for the concentrations of Zn²⁺ ions employed.     

细菌铁载体拮抗植物病原真菌及促生作用研究进展

铁载体是微生物在缺铁条件下分泌的小分子有机化合物,以获取铁元素维持其生长。细菌分泌的铁载体在拮抗植物病原菌和促进植物生长方面具有重要作用。本文总结了细菌铁载体拮抗植物病原真菌的营养和生态位竞争、诱导植物诱导性系统抗性、扰乱病原菌铁稳态的机制,以及促进植物生长的作用,以解释细菌分泌的铁载体在多功能微生物菌剂研制中的重要作用。     

Bacterial siderophores : structure and NMR assignment of pyoverdins Pa,siderophores ofPseudomonas aeruginosa ATCC 15692

Summary In iron-deficient conditions,Pseudomonas aeruginosa ATCC 15692 synthesizes two major siderophores, pyoverdins Pa and pyoverdin Pa B. Two other compounds, pyoverdin Pa A (occurring from hydrolysis of pyoverdin Pa during the culture) and pyoverdin Pa C (occurring artifactually during the purification procedure) were also isolated. All these compounds possess the same partly cyclic peptide chain wherel-Orn(OH · HCO) isN -formyl,N -hydroxy-l-ornithine. The chain is bound to a chromophore derived from 2,3-diamino-6,7-dihydroxyquinoline and having the (S) configuration. The four pyoverdins differ only in the acyl substituent bound to the nitrogen atom bound to carbon C3 of the chromophore. This is succinamide (pyoverdin Pa), succinic acid (pyoverdin Pa A), methyl succinate (pyoverdin Pa C) and 2-oxoglutaric acid (pyoverdin Pa B). The complete¹H- and¹³CNMR assignments, using two-dimensional total correlation NMR spectroscopy (TOCSY) and rotating-frame Overhauser enhancement spectroscopy (ROESY) procedures, as well as¹H-¹³C correlations, are reported. The complete sequence of the peptide using CH-NH correlations was achieved by NMR and confirmed the partly cyclic structure earlier reported using fast-atom-bombardment mass spectrometry (FAB-MS) on the siderophores and their dansylated fragments [Briskot G, Taraz K, Budzikiewicz H (1989)Liebigs Ann Chem: 375–384]. The use of these NMR procedures appears to be a tool of choice and a complementary approach to FAB-MS in the structure determination of some complex pyoverdins.Abbreviations Ser serine - Arg arginine - Thr ethreonine - Lys lysine - OHOrn N -hydroxyornithine - Chr chromophore     

In-vitro and in-vivo analysis of the production of the Bordetella type three secretion system effector A in Bordetella pertussis,Bordetella parapertussis and Bordetella bronchiseptica

Bordetella pertussis, Bordetella parapertussis, and Bordetella bronchiseptica are three closely related pathogens.They all possess the gene coding for the Bordetella type three secretion system effector A (bteA) toxin that became a focus of interest since it was demonstrated that B. pertussis Japanese non-vaccine-type isolates produce BteA unlike vaccine-type isolates. We thus explored the in-vitro production of BteA in B. pertussis isolates collected in France during periods of different vaccine policy as well as in B. parapertussis and B. bronchiseptica isolates. We also analyzed the in-vivo induction of anti-BteA antibodies after infection with different isolates of the three species.We produced a recombinant His6-tagged BteA (rBteA) protein. Specific rBteA polyclonal serum was prepared which enabled us to screen Bordetella isolates for in-vitro BteA production: 99.0% (293/296) of tested B. pertussis isolates, including French vaccine strains, and 97.5% (79/81) of B. bronchiseptica isolates produced BteA in-vitro but only the latter was capable of inducing an in-vivo immune response. No in-vitro or in-vivo production of BteA was detected by any of the B. parapertussis isolates tested.     

Genetic diversity analysis of isolates belonging to Bordetella pertussis, Bordetella parapertussis and Bordetella bronchiseptica species

In this study, Amplified Fragment Length Polymorphism (AFLP) method was used to track differences among human and animal isolates of B. pertussis, B. parapertussis and B. bronchiseptica species. One hundred and sixty representative strains of these species orginated from international and Polish bacterial collections were genotyped according to AFLP involving EcoRI/Msel and SpeI/ApaI restriction/ligation/amplification procedures. This study has confirmed high potential AFLP SpeI/ApaI procedure for intra-species differentiation of B. pertussis and B. bronchiseptica strains. Both AFLP EcoRI/MseI and SpeI/ApaI procedures have been found to be useful for species-specific classification in case of B. pertussis strains. In case of B. bronchiseptica or B. parapertussis species-specific classification, SpeI/ApaI procedure has been found more precise than EcoRI/MseI one.