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51.
Mohamed H. Abd-Alla Shymaa R. bashandy 《World journal of microbiology & biotechnology》2008,24(2):291-292
Tomato fruits and seed lots were screened for the presence of Xanthomonas
vesicatoria and Ralstonia
solanacearum. Yellow colonies of Xanthomonas
vesicatoria and white colonies of Ralstonia
solanacearum were consistently isolated on yeast extract-dextrose-calcium carbonate agar medium (YDC) from diseased fruits and seed samples.
This was confirmed by isolation on semi-selective medium such as Tween B for Xanthomonas and triphenyltetrazolium salt (TTC) medium for Ralstonia
solanacearum followed by biochemical tests. The four isolates belonging to Xanthomonas
vesicatoria and Ralstonia
solanacearum were used to inoculate a local tomato variety. The isolates were found to cause yellowing and wilting of 2-weeks-old seedlings
by 8–14 days after inoculation and by 4 weeks all plants had wilted and completely died. Bacteria with the same characteristics
as those inoculated were reisolated from the infected plants. Uninoculated plants remained healthy. 相似文献
52.
Potato bacterial wilt suppression and plant health improvement after application of different antioxidants 下载免费PDF全文
Shahenda M. A. Farag Kamel M.A. Elhalag Mohamed H. Hagag Abdel Salam M. Khairy Heba M. Ibrahim Moheb T. Saker Nevein A. S. Messiha 《Journal of Phytopathology》2017,165(7-8):522-537
Bacterial wilt caused by Ralstonia solanacearum is a devastating disease that often threatens potato production and exportation. The potential of four antioxidants (seaweed extract (SWE), yeast, chitosan and ascorbic acid (ASA)) in controlling the disease was evaluated in vitro, under glasshouse and field conditions. The field experiment was conducted in two naturally infested locations: Wardan, Giza (sandy soil), and Talia, Minufiya (silty clay soil). Only chitosan showed antibacterial properties against the pathogen in vitro. SWE, yeast and chitosan showed disease suppression under both glasshouse and field conditions. The disease suppression was accompanied by an increase in the ratio of soil copiotrophic to oligotrophic bacteria. The three antioxidants increased plant nitrogen content, decreased soil OM content and decreased C/N ratio. Disease suppression after chitosan application was clearly observed only in Wardan area, which was characterized by a higher soil alkalinity. A high percentage of antagonistic fluorescent strains similar to Pseudomonas putida group were detected for chitosan‐treated plants in Wardan area (sandy soil). ASA drastically decreased the count of the pathogen in soil, but was conducive to the pathogen in plant tissues. A remarkable increase in microbial (bacterial and fungal) soil and rhizosphere diversity as indicated by PCR‐DGGE analysis for bacterial 16S rRNA and fungal 18S rRNA was recorded. In Talia area (silty clay soil), the soil microbial community was more stable and was in general resistant to the disease where the soils were characterized by high electrical conductivity. SWE, yeast and ASA significantly increased crop production in Talia area only. 相似文献
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We previously reported that the activities of two 3-hydroxybutyrate dehydrogenases (BDH1 and BDH2) were greatly influenced
by culture conditions when Ralstonia pickettii T1, a strain growing on extracellular poly-3-hydroxybutyrate (PHB), was grown on different carbon sources such as 3HB and
succinate. In this study, knockout mutants of bdh1 or bdh2 were constructed and characterized under different culture conditions. In addition, a novel BDH (BDH3) was found in bdh2 mutants, and bdh3 was cloned. Apparent kinetic parameters for the substrates of BDH3 indicated that the enzyme is suitable for the oxidation
reaction of 3-hydroxybutyrate (3HB) to acetoacetate. In Western blotting, it was clear that BDH3 is produced only in cells
grown on 3HB or PHB as a carbon source, while BDH1 and BDH2 are produced in cells grown on various carbon sources such as
sugars, amino acids, organic acids, 3HB, and PHB. Both the bdh1 and bdh2 mutants lagged behind the wild type in growth rates when the cells were cultured with 3HB, citrate, succinate, or nutrient
broth. A test of sensitivity to diamide as an oxidative stress revealed that the lack of BDH1 or BDH2 caused a decline in
the capacity to neutralize the stress. These results suggested that BDH1 and BDH2 are needed to regulate the cytoplasmic redox
state as well as to utilize 3HB, while BDH3 is specialized to utilize 3HB. The expression of bdh3 may be coordinately regulated with a gene encoding putative 3HB permease. 相似文献
56.
Ralstonia solanacearum is the causal agent of bacterial wilt in solanaceous crops. This pathogen injects approximately 70 effector proteins into plant cells via the Hrp type III secretion system in an early stage of infection. To identify an as-yet-unidentified avirulence factor possessed by the Japanese tobacco-avirulent strain RS1000, we transiently expressed RS1000 effectors in Nicotiana benthamiana leaves and monitored their ability to induce effector-triggered immunity (ETI). The expression of RipB strongly induced the production of reactive oxygen species and the expressions of defence-related genes in N. benthamiana. The ripB mutant of RS1002, a nalixidic acid-resistant derivative of RS1000, caused wilting symptoms in N. benthamiana. A pathogenicity test using R. solanacearum mutants revealed that the two already known avirulence factors RipP1 and RipAA contribute in part to the avirulence of RS1002 in N. benthamiana. The Japanese tobacco-virulent strain BK1002 contains mutations in ripB and expresses a C-terminal-truncated RipB that lost the ability to induce ETI in N. benthamiana, indicating a fine-tuning of the pathogen effector repertoire to evade plant recognition. RipB shares homology with Xanthomonas XopQ, which is recognized by the resistance protein Roq1. The RipB-induced resistance against R. solanacearum was abolished in Roq1-silenced plants. These findings indicate that RipB acts as a major avirulence factor in N. benthamiana and that Roq1 is involved in the recognition of RipB. 相似文献
57.
Ralstonia eutropha strain H16 is a Gram-negative non-pathogenic betaproteobacterium ubiquitously found in soils and has been the subject of intensive research for more than 50 years. Due to its remarkable metabolically versatility, it utilizes a broad range of renewable heterotrophic resources. The substrate utilization range can be further extended by metabolic engineering as genetic tools are available. It has become the best studied “Knallgas” bacterium capable of chemolithoautotrophic growth with hydrogen as the electron donor and carbon dioxide as the carbon source. It also serves as a model organism to study the metabolism of poly(β-hydroxybutyrate), a polyester which is accumulated within the cells for storage of both carbon and energy. Thermoplastic and biodegradable properties of this polyhydroxyalkanoate (PHA) have attracted much biotechnical interest as a replacement for fossil resource-based plastics. The first applications of R. eutropha aimed at chemolithoautotrophic production of single cell protein (SCP) for food and feed and the synthesis of various PHAs. The complete annotated genome is available allowing systematic biology approaches together with data provided by available omics studies. Besides PHAs, novel biopolymers of 2-hydroxyalkanoates and polythioesters or cyanophycin as well as chemicals such as alcohols, alkanes, alkenes, and further interesting value added chemicals significantly recently extended the range of products synthesized by R. eutropha. High cell density cultivations can be performed without too much effort and the available repertoire of genetic tools is rapidly growing. Altogether, this qualifies R. eutropha strain H16 to become a production platform strain for a large spectrum of products. 相似文献
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The in vivo blending of medium chain length polyhydroxyalkanoates (mcl-PHA) and polyhydroxybutyrate (PHB) was carried out using recombinant Pseudomonas putida after transforming the phbCAB operon of Ralstonia eutropha. The most suitable carbon sources for the production of mcl-PHA and PHB blends were identified to be octanoate and gluconate. The molar fractions of 3-hydroxyoctanoate and 3-hydroxybutyrate in the polymer blends were effectively modulated by controlling the mixing ratio of octanoate and gluconate, thereby producing a composition ranging from 95% mcl-PHA to 78% PHB. 相似文献
60.
青枯菌HPLC分析中样品制备方法的优化 总被引:4,自引:0,他引:4
本文研究了青枯菌细胞的制备方法对细胞生命活力和表面特性的影响。结果表明,在高效离子交换色谱分析(HPLC)中,采用5000×g离心10min收集菌体细胞、超纯水(>16MΩ)悬浮和洗涤青枯菌、重复洗涤二次的制备方法,既可以避免培养基成分造成的干扰,又可以保持青枯菌细胞的生命活力和细胞表面的原有性质。 相似文献