The genome sequence of Xylella fastidiosa, a xylem-limited bacterium causing plant diseases, has been fully sequenced. The genome consists of a 2,679,305-base-pair circular chromosome with 52.7% GC content and two plasmids of 51,158 bp and 1,285 bp. Of the 2,904 predicted coding regions, 47% have putative functions. The bacterium has efficient metabolic functions, utilizing sugars as an energy and carbon source, supporting survival in nutrient-poor xylem sap. Pathogenicity mechanisms include toxins, antibiotics, ion sequestration, and interactions with other bacteria and host cells. Many of these proteins are also found in animal and human pathogens, indicating conserved pathogenic mechanisms. At least 83 genes are bacteriophage-derived, suggesting horizontal gene transfer. Citrus variegated chlorosis (CVC), caused by X. fastidiosa, affects orange trees, with symptoms including leaf variegation and gum-like material. The strain 9a5c, derived from a 1992 isolate, produces CVC symptoms in citrus and other plants. The genome contains genes for various metabolic pathways, including energy metabolism, small molecule metabolism, and transport-related proteins. The bacterium can synthesize a wide range of cofactors and prosthetic groups, including biotin, folic acid, and coenzyme A. The genome encodes proteins involved in adhesion, including EPS and fimbriae, which are likely important for bacterial clumping and adhesion to xylem walls. The bacterium also has genes for adhesins, which may help in binding to plant or insect cell surfaces. The genome contains genes for various transport systems, including ABC transporters and a phosphotransferase system, which are essential for nutrient uptake. The genome also includes prophages, which may contribute to the evolution and transfer of virulence factors. The bacterium lacks avirulence genes, which are typically involved in host-specific pathogenicity. This suggests that X. fastidiosa's pathogenicity may not require host cell infection, as it is transmitted by insect vectors. The complete genome sequence provides insights into the molecular mechanisms of X. fastidiosa pathogenicity and its ability to survive in the xylem. The sequence also allows for comparative studies between plant and animal pathogens at the whole-genome level. The genome has been deposited in GenBank with accession numbers AE003849 (chromosome), AE003850 (pXF1.3), and AE003851 (pXF51). The study was conducted by a network of 34 biology laboratories and one bioinformatics centre in São Paulo, Brazil.The genome sequence of Xylella fastidiosa, a xylem-limited bacterium causing plant diseases, has been fully sequenced. The genome consists of a 2,679,305-base-pair circular chromosome with 52.7% GC content and two plasmids of 51,158 bp and 1,285 bp. Of the 2,904 predicted coding regions, 47% have putative functions. The bacterium has efficient metabolic functions, utilizing sugars as an energy and carbon source, supporting survival in nutrient-poor xylem sap. Pathogenicity mechanisms include toxins, antibiotics, ion sequestration, and interactions with other bacteria and host cells. Many of these proteins are also found in animal and human pathogens, indicating conserved pathogenic mechanisms. At least 83 genes are bacteriophage-derived, suggesting horizontal gene transfer. Citrus variegated chlorosis (CVC), caused by X. fastidiosa, affects orange trees, with symptoms including leaf variegation and gum-like material. The strain 9a5c, derived from a 1992 isolate, produces CVC symptoms in citrus and other plants. The genome contains genes for various metabolic pathways, including energy metabolism, small molecule metabolism, and transport-related proteins. The bacterium can synthesize a wide range of cofactors and prosthetic groups, including biotin, folic acid, and coenzyme A. The genome encodes proteins involved in adhesion, including EPS and fimbriae, which are likely important for bacterial clumping and adhesion to xylem walls. The bacterium also has genes for adhesins, which may help in binding to plant or insect cell surfaces. The genome contains genes for various transport systems, including ABC transporters and a phosphotransferase system, which are essential for nutrient uptake. The genome also includes prophages, which may contribute to the evolution and transfer of virulence factors. The bacterium lacks avirulence genes, which are typically involved in host-specific pathogenicity. This suggests that X. fastidiosa's pathogenicity may not require host cell infection, as it is transmitted by insect vectors. The complete genome sequence provides insights into the molecular mechanisms of X. fastidiosa pathogenicity and its ability to survive in the xylem. The sequence also allows for comparative studies between plant and animal pathogens at the whole-genome level. The genome has been deposited in GenBank with accession numbers AE003849 (chromosome), AE003850 (pXF1.3), and AE003851 (pXF51). The study was conducted by a network of 34 biology laboratories and one bioinformatics centre in São Paulo, Brazil.