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Xanthomonas caspase displays an inherent PARP-like activity.

FEMS Microbiol Lett. 2007 May 22;

Authors: Raju KK, Misra HS, Sharma A

In an earlier study, intracellular accumulation of metabolites such as pyruvate and citrate in Xanthomonas campestris pv. glycines (Xcg) was found to result in a caspase dependent stationary phase rapid cell death (RCD). In the present study, the presence of poly ADP-ribose polymerase (PARP)-like activity associated with caspase-3-like protein of Xcg is reported. This activity was found to be responsible for depletion of cellular NAD(+) levels in RCD-promoting media such as Luria-Bertani medium and starch medium fortified with citrate. Addition of PARP-specific inhibitors such as 3-aminobenzamide to RCD-promoting media restored the intracellular NAD(+) levels and thereby prevented RCD. The inherent association of PARP-like activity with the caspase protein was demonstrated by PARP cellular assay, immuno-precipitation and Western analysis. A truncated polysaccharide deacetylase gene having a caspase-like domain was cloned. The expressed protein though found to be inactive, cross-reacted with human caspase and PARP antibodies. This is the first report demonstrating the presence of a PARP-like activity in a prokaryote and its involvement in cell death.

PMID: 17521358 [PubMed - as supplied by publisher]

6 Filipino students win in int'l science fair
Asianjournal.com, CA - May 24, 2007
... titled "The potential of marine bioluminescent bacteria as anti-bacterial agents against two major rice diseases caused by xanthomonas orzyzae pv. ...

6 Filipino students win in int'l science fair
Asianjournal.com, CA - May 24, 2007
... titled "The potential of marine bioluminescent bacteria as anti-bacterial agents against two major rice diseases caused by xanthomonas orzyzae pv. ...

6 Filipino students win in int'l science fair
Asianjournal.com, CA - May 24, 2007
... titled "The potential of marine bioluminescent bacteria as anti-bacterial agents against two major rice diseases caused by xanthomonas orzyzae pv. ...

6 Filipino students win in int'l science fair
Asianjournal.com, CA - May 24, 2007
... titled "The potential of marine bioluminescent bacteria as anti-bacterial agents against two major rice diseases caused by xanthomonas orzyzae pv. ...

6 Filipino students win in int'l science fair
Asianjournal.com, CA - May 24, 2007
... titled "The potential of marine bioluminescent bacteria as anti-bacterial agents against two major rice diseases caused by xanthomonas orzyzae pv. ...

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Refinement of the Xanthomonas campestris pv. vesicatoria hrpD and hrpE operon structure.

Mol Plant Microbe Interact. 2007 May;20(5):559-67

Authors: Weber E, Berger C, Bonas U, Koebnik R

The plant-pathogenic bacterium Xanthomonas campestris pv. vesicatoria possesses a type III secretion (T3S) system which is encoded in the 23-kb hypersensitive response and pathogenicity (hrp) gene cluster. The T3S system is essential for pathogenicity in susceptible hosts and the induction of the hypersensitive response in resistant plants. In this study, we revisited the operon structure of the right part of the hrp gene cluster. Based on complementation experiments of transposon insertions and reverse-transcription polymerase chain reaction analyses, the hrpD operon contains hrcQ, hrcR, hrcS, and hpaA, whereas hrcD, hrpD6, and hrpE belong to the hrpE operon. We determined the transcriptional start site of the hrpE operon and showed that there is a promoter upstream of hrcD containing a plant-inducible promoter box. Conserved secondary mRNA structures in the intergenic region between hrpD6 and hrpE suggest a posttranscriptional regulated expression of hrpE. Based on comparisons of different hrp gene clusters and the analysis of evolutionary rates, we propose that the hrpE transcriptional unit was integrated into the hrp gene cluster at a later time.

PMID: 17506333 [PubMed - in process]

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Molecular and pathotypic characterization of new Xanthomonas oryzae strains from West Africa.

Mol Plant Microbe Interact. 2007 May;20(5):534-46

Authors: Gonzalez C, Szurek B, Manceau C, Mathieu T, Séré Y, Verdier V

DNA polymorphism analysis and pathogenicity assays were used to characterize strains of Xanthomonas oryzae pv. oryzae and Xanthomonas oryzae pv. oryzicola collected from rice leaves in West Africa. Restriction fragment length polymorphism (RFLP), repetitive sequence-based polymerase chain reaction, fluorescent amplified fragment-length polymorphism (FAFLP) analyses were assessed for molecular characterization, while pathogenicity was tested by leaf clipping and leaf infiltration. Dendrograms were generated for the data sets obtained from RFLP analysis and repetitive polymerase chain reaction suggesting that the interrelationships between strains were dependent on the technique used. In all cases, data showed that African strains of X. oryzae pv. oryzae form a group genetically distant from Asian strains. FAFLP analyses separated the X. oryzae strains into three groups with significant bootstrap values. A specific and intriguing feature of African strains of X. oryzae pv. oryzae is a reduction in the number of insertion sequence elements and transcription activator-like (avrBs3/pthA) effector genes, based on the molecular markers employed in the study. In addition, pathogenicity assays conducted with African strains of X. oryzae pv. oryzae on a series of nearly isogenic lines (NILs) identified three new races. Finally, leaf infiltration assays revealed the capacity of African strains of X. oryzae pv. oryzae to induce a nonhost hypersensitive response in Nicotiana benthamiana, in contrast with Asian X. oryzae pv. oryzae and X. oryzae pv. oryzicola strains. Our results reveal substantial differences between genomic characteristics of Asian and African strains of X. oryzae pv. oryzae.

PMID: 17506331 [PubMed - in process]

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Identification of the flagellar chaperone FlgN in the phytopathogen Xanthomonas axonopodis pathovar citri by its interaction with hook-associated FlgK.

Arch Microbiol. 2007 May 10;

Authors: Khater L, Alegria MC, Borin PF, Santos TM, Docena C, Tasic L, Farah CS, Ramos CH

Genome annotation of the plant pathogen Xanthomonas axonopodis pv. citri (Xac), identified flagellar genes in a 15.7 kb gene cluster. However, FlgN, a secretion chaperone for hook-associated proteins FlgK and FlgL, was not identified. We performed extensive screening of the X. axonopodis pv. citri genome with the yeast two-hybrid system to identify a protein with the characteristics of the flagellar chaperone FlgN. We found a candidate (XAC1990) encoded by an operon for components of the flagellum apparatus that interacted with FlgK. In order to further support this finding, Xac FlgK and XAC1990 were cloned, expressed, and purified. The recombinant proteins were characterized by spectroscopic methods and their interaction in vitro confirmed by pull-down assays. We, therefore, conclude that XAC1990 and its homologs in other Xanthomonas species are, in fact, FlgN proteins. These observations extend the sequence diversity covered by this family of proteins.

PMID: 17492271 [PubMed - as supplied by publisher]

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A novel restriction-modification system from Xanthomonas campestris pv. vesicatoria encodes a m4C-methyltransferase and a nonfunctional restriction endonuclease.

FEMS Microbiol Lett. 2007 May 4;

Authors: Yu YJ, Yang MT

A novel restriction-modification (R-M) system, designated as xveIIRM, from chromosomal DNA of the Xanthomonas campestris pv. vesicatoria strain 7-1 (Xcv7-1) was cloned and characterized. The xveIIRM genes involved in this R-M system are aligned in a tail-to-tail orientation and overlapped by 12 base pairs. XveII methyltransferase gene could encode a 299-amino acid protein (M.XveII) with an estimated mass of 33.7 kDa and was classified to be a member of beta-class of m4C-MTase. M.XveII methylates the second cytosine of the 5'-CCCGGG-3' recognition sequence. The predicted amino acid sequence of the intact XveII endonuclease shared 41.9% identity with SmaI. However, a premature TAA translation termination codon was found in the open reading frame of xveIIR and expected to encode an 18.3 kDa truncated protein. The sequence data are consistent with observation of this study that no SmaI-like restriction activity could be detected in the cell extract of Xcv7-1.

PMID: 17488332 [PubMed - as supplied by publisher]

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Recombinant Expression and Purification of Functional XorII, a Restriction Endonuclease from Xanthomonas oryzae pv. oryzae.

J Microbiol. 2007 Apr;45(2):175-8

Authors: Hwang DK, Cho JY, Chae YK

An endonuclease from Xanthomonas oryzae pathovar oryzae KACC 10331, XorII, was recombinantly produced in Escherichia coli using a T7 system. XorII was purified using a combination of ion exchange and immobilized metal affinity chromatography (IMAC). An optimized washing protocol was carried out on an IMAC in order to obtain a high purity product. The final amount of purified XorII was approximately 2.5 mg/L of LB medium. The purified recombinant XorII was functional and showed the same cleavage pattern as PvuI. The enzyme activity tested the highest at 25 degrees in 50 mM NaCl, 10 mM Tris-HCl, 10 mM MgCl2, and 1 mM dithiothreitol at a pH of 7.9.

PMID: 17483805 [PubMed - in process]

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Antibacterial phenolic compounds from the spines of Gleditsia sinensis Lam.

Nat Prod Res. 2007 May;21(4):283-91

Authors: Zhou L, Li D, Wang J, Liu Y, Wu J

This study was to isolate antibacterial compounds from Gleditsia sinensis Lam. spines through bioassay-guided fractionation (against a Gram-positive bacterium Xanthomonas vesicatoria and a Gram-negative bacterium Bacillus subtilis). The crude ethanol extract of G. sinensis spines was partitioned sequentially with solvents of increasing polarity. The ethyl acetate fraction, which exhibited the most significant antibacterial activities among all the solvent fractions, was further separated by column chromatograph, yielding seven phenolic compounds including ethyl gallate (1) and caffeic acid (7), and five flavonoids, dihydrokaempferol (2), eriodictyol (3), quercetin (4), 3,3',5',5,7-pentahydroflavanone (5) and (-)-epicatechin (6). Compounds 4, 5 and 7 showed moderate inhibitory activities against both bacterial species, with compound 7 having the lowest minimal inhibitory concentration (MIC) of 0.125 mg mL(-1), while compounds 1 and 2 showed a weak inhibitory activity only against B. subtilis (MIC 1.00 mg mL(-1)), and compounds 3 and 6 showed insignificant activity against the two bacteria.

PMID: 17479415 [PubMed - in process]

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Repeat domain diversity of avrBs3/pthA-like genes in Ralstonia solanacearum strains and association with host preferences in the field.

Appl Environ Microbiol. 2007 Apr 27;

Authors: Heuer H, Yin YN, Xue QY, Smalla K, Guo JH

Genes homologous to avrBs3 of Xanthomonas were detected in 309 strains of Ralstonia solanacearum biovars 3, 4 and 5, but not 1 or 2. A statistically significant association between the originating plant species and internal repeats of the gene was found. Sequences of repeats, and variation between nearly clonal strains revealed evidence for frequent recombination.

PMID: 17468277 [PubMed - as supplied by publisher]

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DSF-dependent cell-cell signaling and virulence in the nosocomial pathogen Stenotrophomonas maltophilia.

J Bacteriol. 2007 Apr 27;

Authors: Fouhy Y, Scanlon K, Schouest K, Crossman L, Avison MB, Ryan RP, Dow JM

The genome of Stenotrophomonas maltophilia encodes a cell-cell signaling system that is highly related to the diffusible signal factor (DSF)-dependent system of the phytopathogen Xanthomonas campestris. Here we show that in S. maltophilia, DSF signaling controls factors contributing to virulence and antibiotic resistance of this important nosocomial pathogen.

PMID: 17468254 [PubMed - as supplied by publisher]

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[Analysis of Nonenzymic Source of Superoxide Anion in Pathogenic Xanthomonas oryzae pv. oryzae.]

Zhi Wu Sheng Li Yu Fen Zi Sheng Wu Xue Xue Bao. 2007 Apr;33(2):146-52

Authors: Li X, Li HY, Feng HQ, Wang JS

With electron spin resonance and chemical assay, the production of superoxide anion in the Xanthomonas oryzae pv. oryzae strain OS-14 suspension is extracellularly localized. It was found that superoxide anion produced in the filtrate. It was confirmed that peptide or enzyme did not contribute to the production of superoxide anion in the filtrate of OS-14. Organic acids were shown to be the primary source of superoxide anion produced in the filtrate of OS-14. These results indicated that non-enzymic molecules might be another source of superoxide anion produced by Xanthomonas oryzae pv. oryzae, in addition to enzymes, which suggested the multiform generation of superoxide anion.

PMID: 17452800 [PubMed - in process]

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Ecological impact of solar ultraviolet-B (UV-B: 320-290 nm) radiation on Corynebacterium aquaticum and Xanthomonas sp. colonization on tea phyllosphere in relation to blister blight disease incidence in the field.

Lett Appl Microbiol. 2007 May;44(5):513-9

Authors: Gunasekera TS, Paul ND

Aims: To assess the effects of solar UV-B radiation on phyllosphere bacteria of tea leaves in relation to blister blight disease in the field. Methods and Results: The effects of UV-B radiation on the phyllosphere microbiology of tea (Camellia sinensis) were studied in contrasting wet and dry seasons at a tropical site. Wavelength-selective filters were used to separate the effects of UV-B from those of other factors. Bacterial populations were quantified in relation to the incidence of blister blight disease. Attenuation of UV-B increased the survival of Xanthomonas sp. when populations were not water limited, and increased the incidence of blister blight, but had no effect on Corynebacterium aquaticum. Conclusions: The effects of solar UV-B on phyllosphere bacteria were substantial but depended on both species and interactions with other environmental variables. Xanthomonas sp. was more sensitive to UV-B than C. aquaticum, but this did not result in differences in population density under high radiation conditions (dry season), but only in the wet season when other factors were not limiting. Significance and Impact of the Study: The role of UV-B on leaf surface microbiology in the tropics is marked but depends on other conditions, and the contrasting UV-B responses of different organisms can be masked by other limiting factors.

PMID: 17451518 [PubMed - in process]

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Isolation and characterization of a xanthan-degrading Microbacterium sp. strain XT11 from garden soil.

J Appl Microbiol. 2007 May;102(5):1362-71

Authors: Qian F, An L, Wang M, Li C, Li X

Aims: Isolation and characterization of the xanthan-degrading Microbacterium sp. XT11. Methods and Results: The bacterial isolate XT11, capable of fragmenting xanthan, has been isolated from soil sample. Morphological and biochemical analyses, as well as 16S rRNA gene sequence comparisons, demonstrated that strain XT11 should be grouped in the genus Microbacterium, and represented a new member in this family. Xanthan could be degraded by the xanthan-degrading enzyme released from strain XT11. It has been shown that xantho-oligosaccharides fragmented from xanthan had both elicitor activity and antibacterial effect against Xanthomonas campestris pv. campestris. Conclusions: The xanthan-degrading enzyme produced by the newly isolated XT11 could fragment xanthan to form oligosaccharides. Significance and Impact of the Study: Xanthan-degrading products would be useful for potential application in the control of black rot of cruciferous plants caused by X. campestris pv. campestris and, as an oligosaccharide elicitor, in making these plants resistant to disease.

PMID: 17448171 [PubMed - in process]

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Detection of Xanthomonas oryzae pv. oryzae in Seeds Using a Specific TaqMan Probe.

Mol Biotechnol. 2007 Feb;35(2):119-28

Authors: Zhao WJ, Zhu SF, Liao XL, Chen HY, Tan TW

Xanthomonas oryzae pv. oryzae is the pathogen that causes bacterial leaf blight in rice. Bacterial leaf blight is the main cause for severe rice underproduction in many countries. However, with conventional methods it is difficult to quickly and reliably distinguish this pathogen from other closely related pathogenic bacteria, especially X. oryzae pv. oryzicola, the causal organism of bacterial leaf streak in rice. We have developed a novel and highly sensitive real-time method for the identification of this specific bacteria based on a TaqMan probe. This probe is designed to recognize the sequence of a putative siderophore receptor gene cds specific to X. oryzae pv. oryzae, and can be identified from either a bacterial culture or naturally infected rice seeds and leaves in only 2 h. The sensitivity of the method is 100 times higher than that of the current polymerase chain reaction (PCR) gel electrophoresis method for diagnosis.

PMID: 17435277 [PubMed - in process]