Natural communities Ion Channel Ligand Library clinical trial of microbes associated with chronic infections such as colonization of the cystic fibrosis lung are often highly diverse [10–13]. We also measured the degree of ecological similarity among strains, using commercially available BIOLOG plates that contain 95 different carbon substrates, and show that ecological similarity can decrease with genetic distance. This result is consistent with the idea that toxin production is not favoured among genetically divergent strains because of a lack of resource competition. Pyocins and Pseudomonas aeruginosa P. aeruginosa produces a wide variety of toxins

and among the most interesting, in part because they are known to be highly specific in their action,

are bacteriocins called pyocins. They are costly to produce because Tipifarnib they are released by cell lysis of a fraction of the producer population. Pyocins are proteinaceous compounds that are classified into three groups (R-, F-, and S-type), with multiple sub-types within each group that attach to different potential receptors in target strains [5, 14, 15]. PA01 is known to produce all three pyocins while PA14 produces only R- and F-type pyocins [4]. Genes coding for production of all pyocins are located on the chromosome and are clustered with genes coding for resistance to the same pyocins. Genomic studies have suggested the presence of more pyocins [16–19], both from the S- and R-types. In addition, a recently developed genome-mining tool for bacteriocins has revealed the general existence of yet to be characterized bacteriocins in several bacterial species [20]. Other toxins produced by P. aeruginosa include virulence factors such as exotoxin A, PCN and Y as well as membrane vesicles [21–23]. The clinical strains in our study come from a multi-centre Canadian study of the epidemiology of chronic P. aeruginosa infections of CF patients [24], see Methods. C-X-C chemokine receptor type 7 (CXCR-7) Chronic infection with P. aeruginosa occurs in 60-70% of Canadian adults with CF [25]. After confirmation using standard techniques that the isolates were P. aeruginosa (Methods), genetic distance among all

strains was estimated by comparing banding patterns of a full genome digest using pulsed field gel electrophoresis, PFGE [26–30]. We also confirmed that genetic distance correlates with the degree of overlap in resource use, measured by the ability of strains to metabolize 95 different carbon substrates found on commercially available Biolog plates. Results and discussion We measured the level of inhibition by anticompetitor toxins by spotting a dilution series of a cell free extract collected from 48 h old P. aeruginosa PA01 or PA14 culture onto a lawn of one of 55 different clinical isolates growing on a solid surface. The natural isolates differ in their genetic distance to the producing strain; genetic distance is quantified using full genome digests.