Xylella fastidiosa is a xylem-dwelling, insect-transmitted, gamma-proteobacterium that causes diseases in many plants, including grapevine, citrus, periwinkle, almond, oleander, and coffee. X. fastidiosa has an unusually broad host range, has an extensive geographical distribution throughout the American continent, and induces diverse disease phenotypes. Previous molecular analyses indicated three distinct groups of X. fastidiosa isolates that were expected to be genetically divergent. Here we report the genome sequence of X. fastidiosa (Temecula strain), isolated from a naturally infected grapevine with Pierce's disease (PD) in a wine-grapegrowing region of California. Comparative analyses with a previously sequenced X. fastidiosa strain responsible for citrus variegated chlorosis (CVC) revealed that 98% of the PD X. fastidiosa Temecula genes are shared with the CVC X. fastidiosa strain 9a5c genes. Furthermore, the average amino acid identity of the open reading frames in the strains is 95.7%. Genomic differences are limited to phage-associated chromosomal rearrangements and deletions that also account for the strain-specific genes present in each genome. Genomic islands, one in each genome, were identified, and their presence in other X. fastidiosa strains was analyzed. We conclude that these two organisms have identical metabolic functions and are likely to use a common set of genes in plant colonization and pathogenesis, permitting convergence of functional genomic strategies.Different microorganisms are able to survive in and to colonize plant water-conductive vessels (xylem). The result of this association is either beneficial or detrimental to the plant host.Of the latter, an example is the association of Xylella fastidiosa (38) with diverse plant hosts. X. fastidiosa is a fastidious, insecttransmitted, xylem-inhabiting bacterium known to cause several economically important diseases of both monocotyledonous and dicotyledonous plants (14,17,29). These diseases include Pierce's disease (PD) of grapevine and citrus variegated chlorosis (CVC), which have rather distinct symptoms and geographical distributions.PD, caused by certain strains of X. fastidiosa, is characterized by wilted, shriveled, raisin-like fruit and scorched leaves that detach, leaving bare petioles attached to the canes (37). The bark of affected canes may lignify or mature irregularly, leaving

Background: Cyanobacterial taxonomy has experimented considerable changes due to the exploration of previously uninvestigated regions as well as the introduction of molecular tools. Challenges arose when strains collected from agricultural areas, salt waters and dry limestone did not reveal remarkable morphological differences and had a high level of similarity in the phylogeny of 16S rDNA gene sequences. The aim of the present investigation was to fingerprint members of the genera Calothrix and Nostoc based on the repetitive DNA sequences, as molecular markers for the detection of phylogenetic affinities and molecular diversity. Methods: In this research, through a polyphasic approach, the differences in morphological and genotypic features of different strains were investigated. Bacteria free cyanobacterial clones were prepared followed by morphological characterization, genomic DNA extraction and PCR with 16S rRNA, ERIC, STRR1a and HIP primers. Then the phylogenetic analyses of partial 16S rRNA genes and fingerprints were performed. Results: The results showed each marker producing unique and strain-specific banding pattern, thus highlighting the efficiency of this technique in the assessment of proximity between closely related cyanobacterial strains isolated from different climatic/geographic regions and habitats. Conclusions: This case is the first documented genomic fingerprinting from seven close cyanobacterial strains in Iran.