Comparison of genomic sequences and virulence functions of two Xanthomonas strains. Xanthomonas campestris

Xanthomonas campestris pv. campestris. This organism is the causative agent of crucifer black rot disease, which has an enormous impact on worldwide agriculture. Comparison of these two strains reveals different pathogenic properties on host plants, with ATCC 33913 showing wak virulence on cabbage and radish plants. Comparison of the two genomes expected to show differences in their content. A surprising finding was a massive chromosomal inversion between the two strains that appears to have occurred due to recombination between two insertion sequences (IS1478). Other strain-specific differences included single-nucleotide polymorphisms (3548) in 498 genes, insertions and deletions, and strain-specific chromosomal islands which appear to have been acquired by horizontal gene transfer as inferred by the presence of phage-specific proteins and a difference in GC-content and codon usage. Strain 8004 has two type IV secretion proteins, XC2031 and XC2040, and some transport proteins, XC2405, XC2294, and SC2295 that are specific for that strain. A number of transposition mutants were used to identify virulence functions. A total of 75 nonredundant mutants were obtained, some in what are presumably virulence-related genes (39) and some in intergenic regions that may have affected regulation of downsteam genes (11).