Sesquiterpenes from Chloranthus holostegius with anti-inflammatory activities.

The phytoconstituents of the whole plants of Chloranthus holostegius were investigated. As a result, thirteen undescribed sesquiterpenes (chloranholosins A-M, 1-13), including ten acorane-type sesquiterpenes (1-10), one germacrene-type sesquiterpene (11), and two lindenane-type sesquiterpenes (12-13), together with fifteen known sesquiterpenes were isolated. Their structures and absolute configurations were elucidated by a comprehensive method including the spectroscopic data, electronic circular dichroism (ECD) calculations, and single-crystal X-ray diffraction. Chloranholosin L (12) was elucidated as a rare lindenane-type sesquiterpene featuring 14α-Me and 5-OH moieties. And chloranholosin M (13) was the first lindenane-type sesquiterpene possessing ß-cyclopropane, 14α-Me, and 5ß-H configuration from the family Chloranthaceae. Furthermore, twelve new isolates and some known sesquiterpenes were evaluated for their inhibitory activity against LPS-induced nitric oxide (NO) production in RAW 264.7 macrophage cells. Among them, compounds 12, 16, and 23 showed comparable inhibitory activity to that of the positive control, with IC50 values of 47.9, 41.5, and 48.3 µM, respectively.

Biological Preparation of Chitosan-Loaded Silver Nanoparticles: Study of Methylene Blue Adsorption as Well as Antibacterial Properties under Light.

Human beings have made significant progress in the medical field since antibiotics were widely used. However, the consequences caused by antibiotics abuse have gradually shown their negative effects. Antibacterial photodynamic therapy (aPDT) has the ability to resist drug-resistant bacteria without antibiotics, and as it is increasingly recognized that nanoparticles can effectively solve the deficiency problem of singlet oxygen produced by photosensitizers, the application performance and scope of aPDT are gradually being expanded. In this study, we used a biological template method to reduce Ag+ to silver atoms in situ with bovine serum albumin (BSA) rich in various functional groups in a 50 °C water bath. The aggregation of nanomaterials was inhibited by the protein's multistage structure so that the formed nanomaterials have good dispersion and stability. It is unexpected that we used chitosan microspheres (CMs) loaded with silver nanoparticles (AgNPs) to adsorb methylene blue (MB), which is both a pollutant and photosensitive substance. The Langmuir adsorption isothermal curve was used to fit the adsorption capacity. The exceptional multi-bond angle chelating forceps of chitosan make it have a powerful physical adsorption capacity, and dehydrogenated functional groups of proteins with negative charge can also bond to positively charged MB to form a certain amount of ionic bonds. Compared with single bacteriostatic materials, the bacteriostatic capacity of the composite materials adsorbing MB under light was significantly improved. This composite material not only has a strong inhibitory effect on Gram-negative bacteria but also has a good inhibitory effect on the growth of Gram-positive bacteria poorly affected by conventional bacteriostatic agents. In conclusion, the CMs loaded with MB and AgNPs have some possible applications in the purification or treatment of wastewater in the future.

Surface Self-Assembly of Dipeptides on Porous CaCO3 Particles Promoting Cell Internalization.

The self-assembling behavior of peptides and derivatives is crucial in the natural process to construct various architectures and achieve specific functions. However, the surface or interfacial self-assembly, in particular, on the surface of micro- or nanoparticles is even less systematically investigated. Here, uniform porous CaCO3 microparticles were prepared with different charged, hydrophobic and hydrophilic surfaces to assess the self-assembling behavior of dipeptides composed of various sequences. Experimental results indicate that dipeptides with a negative charge in an aqueous solution preferred to self-assemble on the hydrophobic and positively charged surface of CaCO3 particles, which can be ascribed to the electrostatic and hydrophobic interaction between dipeptides and CaCO3 particles. Meanwhile, the Log p (lipid-water partition coefficient) of dipeptides has a significant effect on the self-assembling behavior of dipeptides on the surface of porous CaCO3; dipeptides with high Log p preferred to self-assemble on the surface of CaCO3 particles, resulting in the improved cell internalization efficiency of particles with low cytotoxicity. After loading with a model drug (doxorubicin), the particles show obvious antitumor activity in animal experiments and can reduce Dox side effects effectively.

Effects of environmental factors on the fleroxacin photodegradation with the identification of reaction pathways.

The abuse of fluoroquinolones (FQs) antibiotics leads to bacterial resistance and environmental pollution, so it is of great significance to verify the decomposition mechanism for eliminating antibiotic efficiently and conveniently. The effects of various environmental factors and the fleroxacin (FLE) photodegradation mechanisms were investigated by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS), UV-Vis absorption spectroscopy, fluorescence spectroscopy and quantum chemical calculation. Six possible photodegradation reaction paths on T1 (excited triplet state) were proposed and simulated. The departure of the piperazine ring and the substitution of F atom at C-6 position by OH group were determined as the main reactions based on the reaction rates and energy barriers of each path. The multi-pathway reactions resulted in the fastest photodegradation rates of FLE at pH 6-7 than other pH conditions. NaN3 would promote FLE photodegradation by inhibiting the reverse reaction of the separation process of F atom at C-8 and the generation of biphenyl molecules, which was a novel and distinctive phenomenon in this report. ·OH would rapidly combine with the free radicals generated in photolysis processes and made a great contribution to FLE photodegradation. Ca2+, Mg2+ and Ba2+ could stabilize the carboxyl group to impede the photo-competitive process of the decarboxylation reaction, while NO3- could generate reactive oxygen species to promote photodegradation.

An avirulent Ralstonia solanacearum strain FJAT1458 outcompetes with virulent strain and induces tomato plant resistance against bacterial wilt.

BACKGROUND: Bacterial wilt (BW) caused by Ralstonia solanacearum (RS) is considered as one of the most destructive plant diseases. An avirulent strain of RS, FJAT1458, is a potential biocontrol agent of BW. In this study, the mechanism of FJAT1458 against BW was evaluated. RESULTS: FJAT1458 was tagged with the red fluorescent protein gene, and the resulting strain was named as FJAT1458-RFP. When FJAT1458-RFP and FJAT91-GFP (a virulent strain of RS labelled with the green fluorescent protein gene), were co-inoculated in potted tomato plants, the colonization of FJAT91-GFP reached an almost undetectable level at 7 days post-inoculation (dpi) in the roots and at 9 dpi in rhizosphere soil. When they were co-inoculated in a hydroponic tomato growing system, numbers of the two strains were similar at 3 dpi in the root tissues; however, FJAT91-GFP was not detected at 9 dpi while FJAT1458-RFP maintained 1.77 × 105 CFU g-1 . The inoculation of FJAT1458-RFP alone or combination with FJAT91-GFP significantly increased tomato root activity. Moreover, expression levels of the defense-related genes PR-1a, GLUA, and CHI3 in tomato roots were significantly up-regulated by FJAT1458-RFP and co-inoculation of FJAT1458-RFP and FJAT91-GFP at 5 dpi, compared to the control (water, CK) treatment. Noteworthy, expression levels of GLUA in the treatments of FJAT1458-RFP and FJAT1458-RFP + FJAT91-GFP were 12.22- and 12.05-fold higher than that in the CK at 5 dpi, respectively. CONCLUSIONS: The results suggested that the avirulent strain FJAT1458-RFP could suppress colonization of the virulent strain in tomato roots, and induce tomato plant resistance against BW. © 2022 Society of Chemical Industry.

Steady/transient state spectral researches on the solvent-triggered and photo-induced novel properties of metal-coordinated phthalocyanines.

The large conjugated system and the d orbitals of metallic phthalocyanines (MPcs) are easily triggered by solvent molecules and light to cause variations in photo-physical and photo-chemical properties. To clarify the novel properties of photo-excited MPcs in solvents, the steady/transient state spectral data were collected to investigate four MPc templates, including FePc, ZnPc, CoPc and AlClPc. The Q bands of FePc and CoPc were prone to redshift, while the peaks of ZnPc and AlClPc tended to blueshift in various solvents compared with that in DMSO. With xenon lamp irradiation, the characteristic absorption peak intensity of FePc and ZnPc in DMSO decreased gradually and then increased after being subjected to dark condition. The transient absorption spectra and kinetic data illustrated that photo-excited FePc and CoPc produced relatively short lifetime transient intermediates. The positive absorption at 650 nm in the Q bands of FePc and CoPc could be assigned to the d-π* electron transition in transient intermediates with unpaired d-orbital electron in the open shell configuration of Fe2+ and Co2+. The above studies were of great significance for the application of solvent-triggered and photo-induced novel properties of MPcs.

The inner oxygen-substituted strategy effects on structure, aromaticity and absorption spectra of corrole isomers: A theoretical study.

Corrole and oxaporphyrin have been successfully synthesized and applied in many research fields such as organic photoelectronics and sensors with the unique photophysical and chemical properties. However, the low synthesis yields of oxacorrole drive researchers turning their attention to theoretical studies for more reasonable molecular structure as the appeal of energy conservation and green chemistry. Corroles, oxacorroles (OC) and dioxacorroles (DOC), a total of 14 molecules, are calculated to systematically explore their structures, intramolecular hydrogen bonds, molecular aromatic and absorption spectral properties influenced by the inner O atoms positions with density functional theory (DFT) and time-dependent density functional theory (TDDFT). The smaller NICS(1)ZZ values of oxacorrole (-35.23 ppm to -33.54 ppm) and dioxacorrole (-34.91 ppm to -33.24) than these of corroles (-32.97 ppm and -33.12 ppm) indicate that the O atoms attendances can increase the molecular aromaticity. The gradually increasing energy gaps of H-8 to H-3 from Corrole1 and Corrole2 to DOC series and the larger charge of CO (+0.208e-+0.380e) than that of CN (+0.065e-+0.177e) illustrate that the substitution of O can reduce the degeneracy degree of energy levels and change the charge distributions. With Hirshfeld method, the molecular orbital contributions of H-1, HOMO, LUMO and L+1 exhibit the regular effects of O atoms positions on orbital energy and electron absorption spectra. For series 1, 23O is beneficial to the red shift of electron absorption spectra. These theoretical conclusions manifest that OC1-23 and DOC1-1 possess the excellent absorption characteristics in the visible region, which can be used as potential materials in the fields of photoelectric materials.

Real-time monitoring of Ralstonia solanacearum infection progress in tomato and Arabidopsis using bioluminescence imaging technology.

BACKGROUND: Ralstonia solanacearum, one of the most devastating bacterial plant pathogens, is the causal agent of bacterial wilt. Recently, several studies on resistance to bacterial wilt have been conducted using the Arabidopsis-R. solanacearum system. However, the progress of R. solanacearum infection in Arabidopsis is still unclear. RESULTS: We generated a bioluminescent R. solanacearum by expressing plasmid-based luxCDABE. Expression of luxCDABE did not alter the bacterial growth and pathogenicity. The light intensity of bioluminescent R. solanacearum was linearly related to bacterial concentrations from 104 to 108 CFU·mL-1. After root inoculation with bioluminescent R. solanacearum strain, light signals in tomato and Arabidopsis were found to be transported from roots to stems via the vasculature. Quantification of light intensity from the bioluminescent strain accurately reported the difference in disease resistance between Arabidopsis wild type and resistant mutants. CONCLUSIONS: Bioluminescent R. solanacearum strain spatially and quantitatively measured bacterial growth in tomato and Arabidopsis, and offered a tool for the high-throughput study of R. solanacearum-Arabidopsis interaction in the future.

Effect of metal ions on lipopeptide secretion from Bacillus subtilis strain FJAT-4: Negative regulation by Ca2.

AIMS: This study aimed to investigate the effect of metal ions on lipopeptide production by Bacillus subtilis strain FJAT-4 and the mechanism of negative regulation by Ca2+ . METHODS AND RESULTS: The quantitative measurement of lipopeptides in response to K+ , Na+ , Mg2+ and Ca2+ addition was carried out by LC-MS. The contents of fengycin and surfactin varied within the range of 116.24-129.80 mg/L and 34.03-63.11 mg/L in the culture media containing K+ , Na+ and Mg2+ , while the levels were 0.86 and 0.63 mg/L in the media containing Ca2+ . Ca2+ at a high concentration (45 mM) did not adversely affect the growth of strain FJAT-4, but caused significant downregulation of lipopeptide synthesis-related gene expression, corresponding to a decrease in lipopeptide production. This inhibition by Ca2+ was further investigated by proteomic analysis. In total, 112 proteins were upregulated and 524 proteins were downregulated in the presence of additional Ca2+ (45 mM). Among these differentially expressed proteins (DEPs), 28 were related to phosphotransferase activity, and 42 were related to kinase activity. The proteomics results suggested that altered levels of three two-component signal-transduction systems (ResD/ResE, PhoP/PhoR and DegU/DegS) might be involved in the control of expression of the fen and srfA operons of FJAT-4 under high calcium stress. CONCLUSIONS: The Ca2+ at the high concentration (45 mM) triggers a decrease in lipopeptide production, which might be attributed to the regulation of three two-component signal-transduction systems ResD/ResE, PhoP/PhoR and DegU/DegS. SIGNIFICANCE AND IMPACT OF THE STUDY: The regulatory effect of calcium on the expression of genes encoding lipopeptide synthetases can be applied to optimize the production of lipopeptides.

Effects of a microbial restoration substrate on plant growth and rhizosphere bacterial community in a continuous tomato cropping greenhouse.

Continuous cropping of tomato is increasingly practiced in greenhouse cultivation, leading to several soil-related obstacles. In this study, a type of microbial restoration substrate (MRS) was used to amend soils from the re-cropping of tomato for 8 years under greenhouse-cultivated conditions. Two treatments were established: using 1,500 kg hm-2 of MRS to amend soil as treatment (TR), and non-MRS as control (CK). The severity of bacterial wilt (BW), soil properties and rhizobacterial community composition under two different treatments were compared. The application of MRS led to an average 83.75% reduction in the severity of BW, and significantly increased the plant height, root activity and yield. Meanwhile, soil pH, soil organic contents (SOC), total nitrogen (TN) and exchangeable calcium were significantly increased (P < 0.05) by MRS treatment. Illumina-MiSeq sequencing analysis of the 16S rRNA genes revealed that MRS increased the diversity of the tomato rhizobacterial community. The relative abundances of Proteobacteria, Actinobacteria and Bacteroidetes were enhanced, whereas those of Acidobacteria, Chloroflexi, TM7 and Firmicutes were decreased by MRS. The redundancy analysis (RDA) revealed that the severity of tomato BW was negatively correlated with the relative abundances of Actinobacteria, Bacteroidetes and Proteobacteria, but positively correlated with those of Gemmatimonadetes, Firmicutes and Acidobacteria. In addition, the effects of MRS on rhizobacterial metabolic potentials were predicted using a Kyoto Encyclopedia of Genes and Genomes (KEGG) database, implying that MRS could significantly increase nitrogen metabolisms and reduce carbon metabolism. Together, our results indicated that the use of MRS could reestablish soil microbial communities, which was beneficial to plant health compared with the control.

Bacillus dafuensis sp. Nov., Isolated from a Forest Soil in China.

A Gram-staining-positive, motile, rod-shaped, aerobic bacterial strain FJAT-25496 T was isolated from a forest soil sample collected from Dafu County, Chengdu City, Sichuan Province, China. Strain FJAT-25496 T grew at 15-50 °C (optimum 35 °C), pH 6.0-10.0 (optimum 8.0), and NaCl tolerance of 0-4.0% (w/v) (optimum 0%). The strain contained iso-C15:0 and anteiso-C15:0 as the predominant cellular fatty acids as well as MK-7 as the only menaquinone. The major polar lipids were diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE), and phosphatidyl glycerol (PG). Phylogenetic analyses based on 16S rRNA gene sequences showed that strain FJAT-25496 T was a member of the genus Bacillus, and most closely related to Bacillus solani FJAT-18043 T (97.8%), Bacillus praedii FJAT-25547 T (97.8%), Bacillus depressus BZ1T (97.7%), Bacillus oceanisediminis H2T (97.7%), and Bacillus ciccensis 5L6T (97.6%). Based on complete genome comparisons between strain FJAT-25496 T and the type strains of its closely related species, the average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values were 73.4-76.3% and 21.7-23.2%, respectively. The genomic DNA G + C content of strain FJAT-25496 T was 36.9%. On the basis of phenotypic, phylogenetic, chemotaxonomic, and genomic features, strain FJAT-25496 T is considered to represent a novel species of the genus Bacillus, for which the name Bacillus dafuensis sp. nov. is proposed. The type strain is FJAT-25496 T (= CCTCC AB 2019182 T = KCTC 43120 T).

Synthesis of polyacrylonitrile nanoflowers and their controlled pH-sensitive drug release behavior.

A novel controlled drug release system based on pH sensitive polyacrylonitrile (PAN) nanoflowers in different kinds of solvents was successfully prepared with azobisisobutyronitrile (AIBN) as the initiator and without any emulsifier or stabilizer by a one step static polymerization method. The composition and structure of the PAN nanoflowers were analyzed by FTIR, XRD, SEM, TEM, and laser particle size analysis. The polymer particles consisted of a number of lamellae, with a sheet thickness of about 10 nm, and were similar to the shape of flowers with a particle diameter of about 350 nm. The mechanism of the polymerization reaction and the formation were studied. Moreover, the effects of monomer ratio, initiator concentration, reaction time, dispersion medium and co-monomer on the morphology and particle size of the nanoflowers were also discussed. A relatively large specific surface area was formed during the formation of the nanoflowers, which favored drug adsorption. The results of the in vitro experiments revealed that PAN(TBP) nanoflowers, containing BSA in buffer solution of pH 7.4, demonstrated good sustained-release and the cumulative release rate was about 83% after 260 h. The results also showed that the sustained-release from the PAN(TBP) nanoflowers best fitted the Riger-Peppas model. This study indicated that PAN(TBP) nanoflowers provided a theoretical base for the development of carriers for sustainable drug-release.

Photo induced reaction of myoglobins with energy transferred from excited free tryptophan.

Despite being one of the most studied proteins in biology, the photolysis mechanism of myoglobin heme affected by endogenous substances free amino acids is still in controversy. The transient absorption and kinetic processes of photo-excited myoglobin in three forms and the effects of free excited tryptophan on redox reaction of myoglobin were monitored by laser flash photolysis. With dual energy superposition of direct light irradiation and indirect energy transferred from the free excited tryptophan, the variation value in optical density (ΔOD) of MetMb increased by 66.7%, from 0.9 to 1.5. The ΔOD value of MbO2 in ferrous form increased from 0.9 to 1.25, while the ΔOD value of DeoxyMb increased from 0.75 to 1.2. The decay time of excited DeoxyMb was prolonged obviously with the excited tryptophan, while the decay time of excited MbO2 and MetMb was shortened significantly. The excited tryptophan could promote laser induced reaction processes of myoglobin in different forms by intermolecular energy transfer to one final similar photo reaction state. The possible photo induced reaction mechanisms of DeoxyMb, MbO2, MetMb with and without free tryptophan were also proposed.

Combined use of a microbial restoration substrate and avirulent Ralstonia solanacearum for the control of tomato bacterial wilt.

Tomato bacterial wilt (BW) caused by Ralstonia solanacearum seriously restricts tomato production and no effective control measures are available. A microbial restoration substrate (MRS) had been proved to be effective control of tomato BW in a greenhouse cultivation. In this study, MRS was combined with an avirulent Ralstonia solanacearum (aRS) strain to control the disease under an open field condition. In the two consecutive year (2017 and 2018) trials, the combined use of aRS and MRS resulted in better disease control compared with either aRS or MRS alone. Moreover, the combined treatment was more effective than expected and suggesting a synergistic control effect. Compared with control (CK, non-aRS or MRS), the application of aRS and MRS treatments alone or in combination could all promote plant growth, increase root activity and yield (e.g. the yield for the treatment of aRS + MRS increased by 463.64% in 2017). Soil nutrients, including soil organic carbon, total nitrogen, total phosphorus and total potassium contents were also significantly increased by the application of aRS and MRS treatments alone or in combination (P < 0.05). The application of MRS or in combination with aRS changed the soil from acidic to neutral, which is one of the key factors for controlling BW. The soil enzymatic activities were notably influenced by the combined use of aRS and MRS, which increased urease (87.37% in 2017 and 60.89% in 2018), catalase (93.67% in 2017 and 279.37% in 2018) and alkaline phosphatase activities (193.77% in 2017 and 455.73% in 2018). These results suggest that the combination of MRS and aRS could effectively control tomato BW and thus represents a promising new tool to control this disease.

MOF-Based Nanotubes to Hollow Nanospheres through Protein-Induced Soft-Templating Pathways.

A controllable and facile strategy is established for constructing metal-organic frameworks-based (MOF-based) hollow composites via a protein-induced soft-templating pathway. Using metal-sodium deoxycholate hydrogel as soft-template, nanotubes are gained while the protein is absent. With the presence of protein, hollow nanospheres structure are prepared by changing the amount of protein. To verify the universality of the proposed pathway, two kinds of proteins (Burkholderia cepacia lipase and penicillin G acylase) and three kinds of MOF (ZIF-8, ZIF-67, and Fe-MOF) are adopted as model proteins and materials, and the obtained protein-containing composites (named protein@H-MOF) possess high bioactivity and stability. This proposed strategy provides a facile method for preparing MOF-based composites under mild conditions, facilitating the applications of MOF in the fields of biocatalyst construction, biomolecule encapsulation, and drug delivery.

Bacterial community diversity associated with the severity of bacterial wilt disease in tomato fields in southeast China.

Tomato bacterial wilt caused by Ralstonia solanacearum is a devastating plant disease. The aims of this study were to investigate the relationship among soil nutrients, rhizobacterial community, and abundance of R. solanacearum, and to gather useful information for controlling the disease. Fifteen tomato rhizosphere soils were collected from three regions, encompassing five disease grades. Then, soil physicochemical properties and rhizobacterial communities were investigated. The content of soil organic carbon (SOC), total phosphorus (TP), total potassium (TK), and exchangeable calcium was significantly higher in the healthy plant rhizosphere soils than in diseased plant rhizosphere soils (P < 0.05). The healthy soils had a relatively higher abundance of Proteobacteria and a lower abundance of Acidobacteria than the diseased soils from the same region. Redundancy analysis demonstrated that R. solanacearum abundance was positively correlated with total nitrogen content and negatively correlated with soil pH, SOC, TP, TK, and exchangeable calcium. Ralstonia solanacearum abundance correlated positively with Chloroflexi, Acidobacteria, and Planctomycetes abundance but negatively with Nitrospirae, Bacteroidetes, and Proteobacteria abundance. These results suggested that improving soil pH, applying the amount of P and K fertilizers, and controlling the dosage of N fertilizer might be an effective approach in controlling bacterial wilt disease.

[Analysis of the heterogeneity of Ralstonia solanacearum avirulent espD-mutant by high performance ion-exchange chromatography].

The heterogeneity of Ralstonia solanacearum avirulent espD-mutant, virulent wildtype strain FJAT-91 and spontaneous avirulent strain FJAT-1458 were compared and analyzed by using high performance ion-exchange chromatography (HPIEC). Their colony and cell morphologies were observed, and the contents of their extracellular polysaccharides (EPS) were determined. The results showed that the colony and cell morphologies of FJAT-91 ⊿epsD were different from the original strain FJAT-91, but were similar to the spontaneous avirulent strain FJAT-1458. The EPS content of FJAT-91 ⊿epsD was (12.64±1.46) µg/mL, which was much lower than FJAT-91 with (30.49±2.97) µg/mL. The strain FJAT-91 were separated into single peak of P3 at the retention time of 6.04 min, and FJAT-91 ⊿epsD had two peaks (P1 and P2) at the retention times of 0.59 min and 4.62 min, respectively. FJAT-1458 formed single peak of P1 at the retention time of 0.59 min. Then, the bacteria eluents from different chromatographic peaks were collected and their pathogenicities were detected with bioassay test using potted tomatoes in the greenhouse. The results showed that the tomato plants began to wilt 4 d after inoculation of strain FJAT-91-P3 eluted from P3, and the disease incidence reached 100% at 10 d post inoculation. The strain FJAT-91 ⊿epsD-P2 eluted from P2 caused tomato plants wilting 9 d after inoculation, and the disease incidence reached 100% at 20 d. During 20 d of observation, none of tomato plants caused wilting while inoculation with FJAT-1458-P1 and FJAT-91 ⊿epsD-P1 eluted from P1 of FJAT-1458 and FJAT-91 ⊿epsD, respectively. In this paper, the morphologies, EPS contents and chromatographic behaviors of FJAT-91, FJAT-91 ⊿epsD and FJAT-1458 were compared, which would provide theoretical basis for using FJAT-91 ⊿epsD to control bacterial wilt disease.

Invasive properties of Ralstonia solanacearum virulent and avirulent strains in tomato roots.

Ralstonia solanacearum causes bacterial wilt disease in a wide range of host plants, including tomato. To elucidate the invasion pattern of R. solanacearum, one avirulent strain, FJAT-1458, and one virulent strain, FJAT-91, were characterized according to their colonization and interaction with host in tomato roots. Both strains colonized in tomato roots. The highest colonization numbers were 1.66 × 108 cfu g-1 by FJAT-91 at 5 days (d) after inoculation and 1.09 × 108 cfu g-1 by FJAT-1458 at 6 d after inoculation. Infection with FJAT-91 caused tomato plant wilt with a disease index of 23.65% at 3 d after inoculation and 100% at 6 d after inoculation, and infection with FJAT-1458 did not cause plant wilt. Compared with FJAT-1458, infection with FJAT-91 reduced elongation of tomato roots, induced serious browning, and overflowed bacteria during the late stages of infection. Examination of cellular structure showed that infection with FJAT-1458 did not have obvious destructive effects on plant cells, while FJAT-91 induced a series of cytopathological changes, including swelling of mitochondria, degeneration of cytoplasm and nuclear heterochromatin, and collapse of host cells, which eventually resulted in the death of the host plant. The cytopathological changes appeared from the second to the fourth disease stages.

Complete Genome Sequence of Ralstonia solanacearum FJAT-91, a High-Virulence Pathogen of Tomato Wilt.

Ralstonia solanacearum FJAT-91, which displays higher virulence toward plants belonging to the family Solanaceae, was isolated from a wilted tomato plant vessel in Fujian province, southeast China. Here, we report the complete genome sequence of R. solanacearum FJAT-91 using long-read single-molecule PacBio sequencing technology. The genome comprises a 3,873,214-bp circular chromosome and a 2,000,873-bp circular megaplasmid with an overall G+C content of 66.85%.

Complete Genome Sequence of Ralstonia solanacearum FJAT-1458, a Potential Biocontrol Agent for Tomato Wilt.

An avirulent strain of Ralstonia solanacearum FJAT-1458 was isolated from a living tomato. Here, we report the complete R. solanacearum FJAT-1458 genome sequence of 6,059,899 bp and 5,241 genes. This bacterial strain is a potential candidate as a biocontrol agent in the form of a plant vaccine for bacterial wilt.