Draft Genome Sequence Of 11399, A Transformable Citrus-pathogenic Strain Of Xylella Fastidiosa

The draft genome of Xylella fastidiosa subsp. pauca strain 11399, a transformable citrus-pathogenic strain, is reported here. The 11399 genome size is 2,690,704 bp and has a G+C content of 52.7%. The draft genome of 11399 reveals the absence of four type I restriction-modification system genes. © 2016 Niza et al.4

The Atp-dependent Rna Helicase Hrpb Plays An Important Role In Motility And Biofilm Formation In Xanthomonas Citri Subsp. Citri

Background: RNA helicases are enzymes that catalyze the separation of double-stranded RNA (dsRNA) using the free energy of ATP binding and hydrolysis. DEAD/DEAH families participate in many different aspects of RNA metabolism, including RNA synthesis, RNA folding, RNA-RNA interactions, RNA localization and RNA degradation. Several important bacterial DEAD/DEAH-box RNA helicases have been extensively studied. In this study, we characterize the ATP-dependent RNA helicase encoded by the hrpB (XAC0293) gene using deletion and genetic complementation assays. We provide insights into the function of the hrpB gene in Xanthomonas citri subsp. citri by investigating the roles of hrpB in biofilm formation on abiotic surfaces and host leaves, cell motility, host virulence of the citrus canker bacterium and growth in planta. Results: The hrpB gene is highly conserved in the sequenced strains of Xanthomonas. Mutation of the hrpB gene (Δ;hrpB) resulted in a significant reduction in biofilms on abiotic surfaces and host leaves. Δ;hrpB also exhibited increased cell dispersion on solid medium plates. Δ;hrpB showed reduced adhesion on biotic and abiotic surfaces and delayed development in disease symptoms when sprayed on susceptible citrus leaves. Quantitative reverse transcription-PCR assays indicated that deletion of hrpB reduced the expression of four type IV pili genes. The transcriptional start site of fimA (XAC3241) was determined using rapid amplification of 5′-cDNA Ends (5′RACE). Based on the results of fimA mRNA structure predictions, the fimA 5′ UTR may contain three different loops. HrpB may be involved in alterations to the structure of fimA mRNA that promote the stability of fimA RNA. Conclusions: Our data show that hrpB is involved in adherence of Xanthomonas citri subsp. citri to different surfaces. In addition, to the best of our knowledge, this is the first time that a DEAH RNA helicase has been implicated in the regulation of type IV pili in Xanthomonas. © 2016 Granato et al.16

Conserved genetic defense response against X. fastidiosa subsp. pauca in olive and citrus

X. fastidiosa subsp. pauca causes diseases in citrus and olive plants. Fortunately, there are citrus species and olive varieties more tolerant to X. fastidiosa and therefore good genotypes to search for genetic sources of resistance. Following this approach, global gene expression analyses were recently achieved using Citrus reticulata cv. Ponkan and Olea europaea cv. Leccino allowing the identification of potential genes involved in plant defense response. Thus, the objective of this work was to identify key genes involved in common genetic defense responses that could be further explored to get resistant varieties. Overall we identified two main mechanisms for both plant species: i. Bacteria recognition and ii. Cell wall fortification. The former involve the expression of patternrecognition receptors, which recognize pathogen molecular patterns and trigger cell defense responses. Some of these receptors belong to the LRR-XII group which contains cell surface immune receptors. The latter involves downregulation of genes in tolerant host such as expansin, pectate lyases and polygalacturonases, related with cell wall expansion and degradation. This suggests that in tolerant hosts, plant cell recognizes X. fastidiosa and reprograms the cell wall development to impair its colonization through the xylem vessels. Therefore these genes represent good candidates to be explored aiming their use in breeding and/or genetic engineering program. Giampetruzzi A., Morelli M., Saponari M., Loconsole G., Chiumenti M., Boscia D., Savino V.N., Martelli G.P. & Saldarelli P. 2016. Transcriptome profiling of two olive cultivars in response to infection by the CoDiRO strain of Xylella fastidiosa subsp. pauca. BMC Genomics 17:475. Rodrigues C.M., De Souza A.A., Takita M.A., Kishi L.T. & Machado M.A. 2013. RNA-Seq analysis of Citrus reticulata in the early stages of Xylella fastidiosa infection reveals auxin-related genes as a defense response. BMC Genomics 14: 676

Global Expression Profile Of Biofilm Resistance To Antimicrobial Compounds In The Plant-pathogenic Bacterium Xylella Fastidiosa Reveals Evidence Of Persister Cells

Investigations of biofilm resistance response rarely focus on plant-pathogenic bacteria. Since Xylella fastidiosa is a multihost plant-pathogenic bacterium that forms biofilm in the xylem, the behavior of its biofilm in response to antimicrobial compounds needs to be better investigated. We analyzed here the transcriptional profile of X. fastidiosa subsp. pauca in response to inhibitory and subinhibitory concentrations of copper and tetracycline. Copper-based products are routinely used to control citrus diseases in the field, while antibiotics are more widely used for bacterial control in mammals. The use of antimicrobial compounds triggers specific responses to each compound, such as biofilm formation and phage activity for copper. Common changes in expression responses comprise the repression of genes associated with metabolic functions and movement and the induction of toxin-antitoxin systems, which have been associated with the formation of persister cells.Ourresults also show that these cells were found in the population at a ca. 0.05% density under inhibitory conditions for bothantimicrobial compounds and that pretreatment with subinhibitory concentration of copper increases this number. No previousreport has detected the presence of these cells in X. fastidiosa population, suggesting that this could lead to a multidrugtolerance response in the biofilm under a stressed environment. This is a mechanism that has recently become the focusof studies on resistance of humanpathogenic bacteria to antibiotics and, based on our data, it seems to be more broadlyapplicable. © 2012, American Society for Microbiology.1941745614569Aakra, A., Transcriptional response of Enterococcus faecalis V583 to erythromycin (2005) Antimicrob. 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Environ. Microbiol., 76, pp. 4250-4259Correia, F.F., Kinase activity of overexpressed HipA is required for growth arrest and multidrug tolerance in Escherichia coli (2006) J. Bacteriol., 188, pp. 8360-8367Costerton, J.W., Lewandowski, Z., Caldwell, D.E., Korber, D., Lappin, S., Microbial biofilms (1995) Annu. Rev. Microbiol., 49, pp. 711-745Davis, M.J., French, J.W., Schaad, N.W., Axenic culture of the bacteria associated with phony disease of peach and plum scald (1981) Curr. Microbiol., 5, pp. 311-316Denou, E., The role of prophage for genome diversification within a clonal lineage of Lactobacillus johnsonii: characterizationof the defective prophage LJ771 (2008) J. Bacteriol., 190, pp. 5806-5813Souza, A.A.D., Takita, M.A., Pereira, E.O., Coletta-Filho, H.D., Machado, M.A., Expression of pathogenicity-related genes of Xylella fastidiosa in vitro and in planta (2005) Curr. Microbiol., 50, pp. 223-228Goh, E.B., Transcriptional modulation of bacterial gene expression by subinhibitory concentrations of antibiotics (2002) Proc. Natl. Acad.Sci.U. S. A., 99, pp. 17025-17030Guilhabert, M.R., Kirkpatrick, B.C., Identification of Xylella fastidiosa antivirulence genes: hemagglutinin adhesins contribute to X (2005) fastidiosa biofilm maturation and colonization and attenuate virulence. Mol. Plant-Microbe Interact., 18, pp. 856-868Hong, S.H., Wang, X., O'connor, H.F., Benedik, M.J., Wood, T.K., Bacterial persistence increases as environmental fitness decreases (2012) Microbial Biotechnol., , doi:10.1111/j.1751-7915.2011.00327.xKasari, V., Kurg, K., Margus, T., Tenson, T., Kaldalu, N., The Escherichia coli mqsR and ygiT genes encode a new toxin-antitoxin pair (2010) J. Bacteriol., 192, pp. 2908-2919Keren, I., Shah, D., Spoering, A., Kaldalu, N., Lewis, K., Specialized persister cells and the mechanism of multidrug tolerance in Escherichia coli (2004) J. 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A., 103, pp. 19484-19489Mah, T.C., O'toole, G.A., Mechanisms of biofilm resistance to antimicrobial agents (2001) Trends Microbiol., 9, pp. 34-39Mitchell, H.L., Treponema denticola biofilm-induced expression of a bacteriophage, toxin-antitoxin systems and transposases (2010) Microbiology, 156, pp. 774-788Newman, K.L., Almeida, R.P.P., Purcell, A.H., Lindow, S.E., Use of a green fluorescent strain for analysis of Xylella fastidiosa colonization of Vitis vinifera (2003) Appl. Environ. Microbiol., 69, pp. 7319-7327Provvedi, R., Boldrin, F., Falciani, F., Palu, G., Manganelli, R., Global transcriptional response to vancomycin in Mycobacterium tuberculosis (2009) Microbiology, 155, pp. 1093-1102Rodrigues, C.M., Copper resistance of biofilm cells of the plant pathogen Xylella fastidiosa (2008) Appl. Microbiol. 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Microbiol., 71, pp. 8491-8499Schumacher, M.A., Molecular mechanisms of HipA-mediated multidrug tolerance and its neutralization by HipB (2009) Science, 323, pp. 396-401Sevin, E.W., Barloy-Hubler, F., RASTA-Bacteria: a web-based tool for identifying toxin-antitoxin loci in prokaryotes (2007) Genome Biol., 8, pp. R155Shah, D., Persisters: a distinct physiological state of Escherichia coli (2003) BMC Microbiol., 6, p. 53. , doi:10.1186/1471-2180-6-53Simpson, A.J.G., The genome sequence of the plant pathogen Xylella fastidiosa (2000) Nature, 40, pp. 151-159Teitzel, G.M., Parsek, M.R., Heavy metal resistance of biofilm and planktonic Pseudomonas aeruginosa (2003) Appl. Environ. Microbiol., 69, pp. 2313-2320Voegel, T.M., Warren, G.J., Matsumoto, A., Igo, M.M., Kirkpatrick, B.C., Localization and characterization of Xylella fastidiosa hemagglutinin adhesins (2010) Microbiology, 156, p. 2172Voloudakis, A.E., Reignier, T.M., Cooksey, D.A., Regulation of resistance to copper in Xanthomonas axonopodis pv (2005) vesicatoria. App. Environ.Microbiol., 71, pp. 782-789Wang, X., Wood, T.K., Toxin/Antitoxin systems influence biofilm and persister cell formation and the general stress response (2010) Appl. Environ.Microbiol., 77, pp. 5577-558

Copper Resistance Of Biofilm Cells Of The Plant Pathogen Xylella Fastidiosa

Xylella fastidiosa is a phytopathogen that causes diseases in different plant species. The development of disease symptoms is associated to the blockage of the xylem vessels caused by biofilm formation. In this study, we evaluated the sensitivity of biofilm and planktonic cells to copper, one of the most important antimicrobial agents used in agriculture. We measured the exopolysaccharides (EPS) content in biofilm and planktonic cells and used real-time reverse transcription polymerase chain reaction to evaluate the expression of the genes encoding proteins involved in cation/multidrug extrusion (acrA/B, mexE/czcA, and metI) and others associated with different copper resistance mechanisms (copB, cutA1, cutA2, and cutC) in the X. fastidiosa biofilm formed in two different media. We confirmed that biofilms are less susceptible to copper than planktonic cells. The amount of EPS seems to be directly related to the resistance and it varies according to the media where the cells are grown. The same was observed for gene expression. Nevertheless, some genes seem to have a greater importance in biofilm cells resistance to copper. Our results suggest a synergistic effect between diffusion barriers and other mechanisms associated with bacterial resistance in this phytopathogen. 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Expression Of Xylella Fastidiosa Rpff In Citrus Disrupts Signaling In Xanthomonas Citri Subsp. Citri And Thereby Its Virulence

Xylella fastidiosa and Xanthomonas citri subsp. citri, that cause citrus variegated chlorosis (CVC) and citrus canker diseases, respectively, utilize diffusible signal factor (DSF) for quorum sensing. DSF, produced by RpfF, are similar fatty acids in both organisms, although a different set of genes is regulated by DSF in each species. Because of this similarity, Xylella fastidiosa DSF might be recognized and affect the biology of Xanthomonas citri. Therefore, transgenic Citrus sinensis and Carrizo citrange plants overexpressing the Xylella fastidiosa rpfF were inoculated with Xanthomonas citri and changes in symptoms of citrus canker were observed. X. citri biofilms formed only at wound sites on transgenic leaves and were thicker; however, bacteria were unable to break through the tissue and form pustules elsewhere. Although abundant growth of X. citri occurred at wound sites on inoculated transgenic leaves, little growth was observed on unwounded tissue. Genes in the DFS-responsive core in X. citri were downregulated in bacteria isolated from transgenic leaves. DSF-dependent expression of engA was suppressed in cells exposed to xylem sap from transgenic plants. Thus, altered symptom development appears to be due to reduced expression of virulence genes because of the presence of antagonists of DSF signaling in X. citri in rpfF-expressing plants.271112411252An, G., Ebert, P.R., Miltra, A., Ha, S.B., Binary vectors (1988) Plant Molecular Biology Manual, A3, pp. 1-19. , S. B. Gelvin, R. A. Schilperoort, and D. P. S. Verma, eds. Kluwer, Dordrecht, The NetherlandsBeaulieu, E.D., Ionescu, M., Chatterjee, S., Yokota, K., Trauner, D., Lindow, S., (2013) Characterization of a Diffusible Signaling Factor (DSF) from Xylella Fastidiosa, , mBio 4:e00539-12Brunings, A.M., Gabrieal, D.W., Xanthomonas citri: Breaking the surface (2003) Mol. 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