Figure 4

Poor correlation between PA14-pathogenicity genes and virulence in other strains. (a) C. elegans survival curves in the presence of 19 P. aeruginosa strains and OP50 (an E. coli control). The names of each strain tested are sorted according to the rank order of virulence, from most virulent at the top to the least virulent at the bottom, as determined by examining the time required to kill 50% of the nematodes. Black brackets indicate strains with indistinguishable virulence. Strain names are followed by the strain source and color-coded by strain source, as shown in panel b. Strain CF27 is not shown in this dataset; however, a similar experiment places its rank order virulence between strains E2 and S36004 (indicated by a black arrow). The same relative rank orders were obtained in two additional experiments. (b) Dendrogram representing the relatedness of 20 P. aeruginosa strains based on the presence or absence of genes as assayed by genomic DNA hybridizations to a custom microarray. Hierarchical clustering analysis was performed using the city-block distance metric. The name of each strain is shown, along with the source of the strain (UTI, urinary tract infection; CF, cystic fibrosis respiratory infection; env, environmental isolate), and the rank order virulence of each strain as determined in panel a (1, most virulent; 20, least virulent). Strains with indistinguishable virulence were given a tied rank order (also see Table 2). (c) Presence or absence of PA14 virulence genes in additional isolates. Data for each strain tested is presented in columns. Strains are arranged in order from left to right in order of decreasing virulence, in the same order as shown in panel a; column headers refer to the 20 strain numbers used in Table 2. Columns with no gaps between them represent groups of strains with indistinguishable virulence (strains 4 and 5; strains 8, 9 and 10; and strains 14, 15 and 16). Genes assayed are represented as rows, with adjacent rows representing ORFs present within a given gene cluster (PA14 region names shown on the left are abbreviated to remove the 'PA14' prefix). Each gene is described as present (blue), absent (yellow), or indeterminate (red). The positions of mutations resulting in reduced virulence in PA14 are indicated by lines to the right; numbers in black refer to entries in Table 3, and red numbers in parenthesis indicate the Spearman's rank correlation coefficients between presence or absence of the gene in other strains and their rank order virulence ratings.