T4SS pili encoded by Haemophilus spp. genomic islands. Presented are transmission electron micrographs of negatively stained samples, showing presence of type IV secretion system (T4SS) dependent pili (arrows) in the Haemophilus spp. strains harboring genomic islands. Three parent Haemophilus spp. strains with the highest conjugation transfer frequencies harboring genomic islands (a) ICEHin1056, (b) ICEHin299, and (c) ICEHpaT3T1 were shown to produce the T4SS pilus. Moreover, H. influenzae strain Rd harboring genomic islands (d) ICEHin1056, (e) ICEHin299, (f) ICEHin2866, (g) ICEHpa8f, (h) and ICEHpaT3T1 produced T4SS pili, thus providing experimental evidence of the activity of T4SS encoded by these genomic islands. Bars represent 100 nm. B, bacterium; ICE, integrative and conjugative element.