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Endophytic bacteria, which are the subject of this study, serve as natural antifungal agents in the struggle against fungal infections, offering an eco-friendly alternative to chemical fungicides. So, it was aimed to determine the antifungal capacities of endophytic bacteria from Aronia ×prunifolia roots in the study. 25 endophytic bacteria were isolated, and their ability to act as biocontrol agents was evaluated by measuring fungal growth inhibition and chemical properties. Later, bacteria that showed a positive effect were identified through 16S gene sequencing. The results showed that the LB2 bacteria had the greatest ability to inhibit the selected fungi and the biochemical tests showed that the bacteria were Gramnegative, did not form spores, their colonies were well defined, and they could break down starch and gelatin, which was later diagnosed as Pseudomonas brassicacearum according to phylogenetic relationships. This study is the first report on which P. brassicacearum was isolated from A. ×prunifolia roots for the first time. These findings contribute to our understanding of the potential of endophytic bacteria, particularly P. brassicacearum, as natural antifungal agents in plant and human protection, offering a promising and sustainable approach to combat fungal infections while reducing the use of chemical fungicides. [ABSTRACT FROM AUTHOR]

By decreasing root 1-aminocyclopropane-1-carboxylate (ACC) content and plant ethylene production, the microbial enzyme ACC deaminase is a widespread beneficial trait of plant growth-promoting rhizobacteria (PGPR), ameliorating ethylene-mediated root growth inhibition. However, relatively little is known about whether bacterial ACC deaminase modulates root architecture and root hair traits. Thus the dwarf tomato (Solanum lycopersicum) cultivar Micro-Tom was inoculated in vitro with Pseudomonas brassicacearum Am3, its ACC deaminase deficient mutant T8-1, a known PGPR strain Variovorax paradoxus 5C-2 or chemically treated with agents that promoted or inhibited ethylene production or sensitivity (Ag+, Co2+, and ACC). ACC treatment reduced both root elongation and the number of lateral roots, while ethylene inhibitors (Ag+, Co2+) and V. paradoxus 5C-2 promoted primary root elongation, but differentially affected lateral root length and number. Ag+ stimulated lateral root development, while Co2+ and V. paradoxus 5C-2 did not. Inoculation with P. brassicacearum Am3 and T8-1 inhibited elongation of the primary and lateral roots at a high inoculum concentration (106 cells cm3). All bacterial strains significantly increased the length and number of root hairs, with these effects more pronounced in P. brassicacearum Am3 than in the mutant T8-1. Treatment with Ag+ inhibited root hair formation and elongation, while Co2+ had the opposite effects. ACC treatment had no effect on root hair elongation but increased root hair density. While root growth inhibition caused by P. brassicacearum Am3 was independent of ACC deaminase, the promotion of root hair elongation and density by this strain was augmented by ACC deaminase activity. Thus ACC deaminase can modulate the morphological impacts of bacteria on root hair response by affecting plant ethylene content. [ABSTRACT FROM AUTHOR]

By decreasing root 1-aminocyclopropane-1-carboxylate (ACC) content and plant ethylene production, the microbial enzyme ACC deaminase is a widespread beneficial trait of plant growth-promoting rhizobacteria (PGPR), ameliorating ethylene-mediated root growth inhibition. However, relatively little is known about whether bacterial ACC deaminase modulates root architecture and root hair traits. Thus the dwarf tomato (Solanum lycopersicum) cultivar Micro-Tom was inoculated in vitro with Pseudomonas brassicacearum Am3, its ACC deaminase deficient mutant T8-1, a known PGPR strain Variovorax paradoxus 5C-2 or chemically treated with agents that promoted or inhibited ethylene production or sensitivity (Ag+, Co2+, and ACC). ACC treatment reduced both root elongation and the number of lateral roots, while ethylene inhibitors (Ag+, Co2+) and V. paradoxus 5C-2 promoted primary root elongation, but differentially affected lateral root length and number. Ag+ stimulated lateral root development, while Co2+ and V. paradoxus 5C-2 did not. Inoculation with P. brassicacearum Am3 and T8-1 inhibited elongation of the primary and lateral roots at a high inoculum concentration (106 cells cm3). All bacterial strains significantly increased the length and number of root hairs, with these effects more pronounced in P. brassicacearum Am3 than in the mutant T8-1. Treatment with Ag+ inhibited root hair formation and elongation, while Co2+ had the opposite effects. ACC treatment had no effect on root hair elongation but increased root hair density. While root growth inhibition caused by P. brassicacearum Am3 was independent of ACC deaminase, the promotion of root hair elongation and density by this strain was augmented by ACC deaminase activity. Thus ACC deaminase can modulate the morphological impacts of bacteria on root hair response by affecting plant ethylene content. [ABSTRACT FROM AUTHOR]

This study was carried out to determine the effects of antagonistic bacteria, which were obtained from the soil rhizosphere and have the strong abilities to dissolve phosphorus and reduce nitrogen, on the white mold disease agent Sclerotinia sclerotiorum (Lib.) de Bary. In the study, ten antagonistic bacteria of the genus Pseudomonas were used. In the in vitro study, the tested antagonistic bacteria suppressed the mycelial growth of S. sclerotiorum by 65.49-88.25%. Isolates with a high inhibition rate on mycelial growth were also effective on the viability of the sclerotia of the pathogenic fungus. Five bacterial isolates caused complete sclerotia viability loss for S. sclerotiorum. According to the result of the in vitro studies, antagonistic bacterial isolates with strong effects on the pathogenic fungus were selected and assayed in pot studies under greenhouse conditions. In pot studies, single treatments with Pseudomonas chlororaphis (R-7) and the dual treatments with Pseudomonas brassicacearum + Pseudomonas chlororaphis (R-3 + R-7) were the most effective against white mold disease. The results of this study show that these antagonistic bacteria can be used in the biological control of S. sclerotiorum. In addition to the in vitro and in vivo studies, it is necessary to determine the performances of antagonistic bacterial isolates, which had the highest effect on white mold disease, in greenhouses and field conditions. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the plant growth-promoting potential of the nodule endophytic Pseudomonas brassicacearum strain Zy-2-1 when used as a co-inoculant of Medicago lupulina with Sinorhizobium meliloti under copper (Cu) stress conditions. Strain Zy-2-1 was capable of producing ACC deaminase activity, IAA and siderophores, and was able to grow in the presence of Cu up to 2.0 mmol/L. Co-inoculation of S. meliloti with Zy-2-1 enhanced M. lupulina root fresh weight, total plant dry weight, number of nodules, nodule fresh weight and nitrogen content in the presence of 100 or 300 mg/kg Cu. In the presence of 500 mg/kg Cu, co-inoculation with S. meliloti and strain Zy-2-1 increased plant height, number of nodules, nodule fresh weight and nitrogen content in comparison to S. meliloti inoculation alone. Furthermore, a higher amount of Cu accumulation in both shoots and roots and a higher level of Cu translocation to shoots were observed in co-inoculated plants. These results demonstrate that co-inoculation of M. lupulina with S. meliloti and P. brassicacearum Zy-2-1 improves plant growth, nitrogen nutrition and metal extraction potential. This can be of practical importance in the remediation of heavy metal-contaminated soils. [ABSTRACT FROM AUTHOR]

Based on a full-sized sequence of the genome of Pseudomonas brassicacearum BIM В-446 bacteria, we determined the nucleotide sequence of the locus encoding the synthesis of the 2,4-diacetylphloroglucinol antibiotic. It was shown in the limits of a nucleotide sequence with 9087 bp size to be localized at open reading frames homologous (96-99% identical residues) to structural ( phlA, phlC, phlB, phlD, phlE, and phlI) and regulatory ( phlF, phlG, and phlH) genes of Pseudomonas brassicacearum and Pseudomonas fluorescens bacteria, which determine the production of 2,4-diacetylphloroglucinol. It emerged that closely related phl-operons differ by their environment. Thus, different genes were localized on the 3'-end. It was determined that inactivation of the phlA gene in P. brassicacearum BIM bacteria caused a loss of the ability to synthesize antibiotic and inhibited the growth of the phytopathogenic Fusarium culmorum, F. oxysporum, and Botrytis cinerea fungi; the antimicrobial activity was also decreased toward with fungal ( Alternaria alternate) and bacterial pathogens ( Pseudomonas syringae and Pectobacterium carotovorum). During inactivation of the phlF regulatory gene, which determines the synthesis of the phl-operon transcription repressor, the production of 2,4-diacetylphloroglucinol was increased. In contrast to the wild-type bacteria, phlF-mutants synthesized an antibiotic that was found in cultural liquid after 12 h of cultivation; its content reached the maximum in medium with saccharose as the carbon source. [ABSTRACT FROM AUTHOR]

The genome of Pseudomonas thivervalensis LMG 21626 has been sequenced and a genomic, genetic and structural analysis of the siderophore mediated iron acquisition was undertaken. Pseudomonas thivervalensis produces two structurally new siderophores, pyoverdine PYO which is typical for P. thivervalensis strains and a closely related strain, and the lipopeptidic siderophore histicorrugatin which is also detected in P. lini. Histicorrugatin consists out of an eight amino acid long peptide which is linked to octanoic acid. It is structurally related to the siderophores corrugatin and ornicorrugatin. Analysis of the proteome for TonB-dependent receptors identified 25 candidates. Comparison of the TonB-dependent receptors of P. thivervalensis with the 17 receptors of its phylogenetic neighbor, P. brassicacearum subsp. brassicacearum NFM 421, showed that NFM 421 shares the same set of receptors with LMG 21626, including the histicorrugatin receptor. An exception was found for their cognate pyoverdine receptor which can be explained by the observation that both strains produce structurally different pyoverdines. Mass analysis showed that NFM 421 did not produce histicorrugatin, but the analogue ornicorrugatin. Growth stimulation assays with a variety of structurally distinct pyoverdines produced by other Pseudomonas species demonstrated that LMG 21626 and NFM 421 are able to utilize almost the same set of pyoverdines. Strain NFM 421 is able utilize two additional pyoverdines, pyoverdine of P. fluorescens Pf0-1 and P. citronellolis LMG 18378, these pyoverdines are probably taken up by the FpvA receptor of NFM 421. [ABSTRACT FROM AUTHOR]

Plant growth-promoting rhizobacteria (PGPR) play an important role in the biodegradation of natural and xenobiotic organic compounds in soil. They can also alter heavy metal bioavailability and contribute to phytoremediation in the presence or absence of synthetic metal chelating agents. In this study, the inhibitory effect of Cd and Ni at different concentrations of Ca and Mg, and the influence of the widely used chelator EDTA on growth of the PGPR Pseudomonas brassicacearum in a mineral salt medium with a mixture of four main plant exudates (glucose, fructose, citrate, succinate) was investigated. Therefore, the bacteriostatic effect of Cd, Ni and EDTA on the maximum specific growth rate and the determination of EC50 values was used to quantify inhibitory impact. At high concentrations of Ca (800 μmol L) and Mg (1,250 μmol L), only a small inhibitory effect of Cd and Ni on growth of P. brassicacearum was observed (EC50 Cd, 18,849 ± 80 μmol L; EC50 Ni, 3,578 ± 1,002 μmol L). The inhibition was much greater at low concentrations of Ca (25 μmol L) and Mg (100 μmol L) (EC50 Cd, 85 ± 0.5 μmol L and EC Ni, 62 ± 1.8 μmol L). For the chosen model system, a competitive effect of the ions Cd and Ca on the one hand and Ni and Mg on the other hand can be deduced. However, the toxicity of both, Cd and Ni, could be significantly reduced by addition of EDTA, but if this chelating agent was added in stoichiometric excess to the cations, it also exhibited an inhibitory effect on growth of P. brassicacearum. [ABSTRACT FROM AUTHOR]

In the beneficial plant root-associated Pseudomonas brassicacearum strain NFM421, the GacS/GacA two-component system positively controls biofilm formation and the production of secondary metabolites through the synthesis of rsmX, rsmY and rsmZ. Here, we evidenced the genetic amplification of Rsm sRNAs by the discovery of a novel 110-nt long sRNA encoding gene, rsmX-2, generated by the duplication of rsmX-1 (formerly rsmX). Like the others rsm genes, its overexpression overrides the gacA mutation. We explored the expression and the stability of rsmX-1, rsmX-2, rsmY and rsmZ encoding genes under rich or nutrient-poor conditions, and showed that their amount is fine-tuned at the transcriptional and more interestingly at the post-transcriptional level. Unlike rsmY and rsmZ, we noticed that the expression of rsmX-1 and rsmX-2 genes was exclusively GacA-dependent. The highest expression level and longest half-life for each sRNA were correlated with the highest ppGpp and cyclic-di-GMP levels and were recorded under nutrient-poor conditions. Together, these data support the view that the Rsm system in P. brassicacearum is likely linked to the stringent response, and seems to be required for bacterial adaptation to nutritional stress. [ABSTRACT FROM AUTHOR]

The genus Pseudomonas comprises many known plant-associated microbes with plant growth promotion and disease suppression properties. Genome-based studies allow the prediction of the underlying mechanisms using genome mining tools and the analysis of the genes unique for a strain by implementing comparative genomics. Here, we provide the genome sequence of the strain Pseudomonas brassicacearum 3Re2-7, formerly known as P. trivialis and P. reactans, elucidate its revised taxonomic classification, experimentally verify the gene predictions by transcriptome sequencing, describe its genetic biocontrol potential and contextualize it to other known Pseudomonas biocontrol agents. The P. brassicacearum 3Re2-7 genome comprises a circular chromosome with a size of 6,738,544 bp and a GC-content of 60.83%. 6267 genes were annotated, of which 6113 were shown to be transcribed in rich medium and/or in the presence of Rhizoctonia solani. Genome mining identified genes related to biocontrol traits such as secondary metabolite and siderophore biosynthesis, plant growth promotion, inorganic phosphate solubilization, biosynthesis of lipo- and exopolysaccharides, exoproteases, volatiles and detoxification. Core genome analysis revealed, that the 3Re2-7 genome exhibits a high collinearity with the representative genome for the species, P. brassicacearum subsp. brassicacearum NFM421. Comparative genomics allowed the identification of 105 specific genes and revealed gene clusters that might encode specialized biocontrol mechanisms of strain 3Re2-7. Moreover, we captured the transcriptome of P. brassicacearum 3Re2-7, confirming the transcription of the predicted biocontrol-related genes. The gene clusters coding for 2,4-diacetylphloroglucinol (phlABCDEFGH) and hydrogen cyanide (hcnABC) were shown to be highly transcribed. Further genes predicted to encode putative alginate production enzymes, a pyrroloquinoline quinone precursor peptide PqqA and a matrixin family metalloprotease were also found to be highly transcribed. With this study, we provide a basis to further characterize the mechanisms for biocontrol in Pseudomonas species, towards a sustainable and safe application of P. brassicacearum biocontrol agents. [ABSTRACT FROM AUTHOR]