Fig 2.

Type IV pili are required for PA14 PIP infection. (A) PIP zone of clearing on strain PA14 with resistant strains growing within the lysis zone (white arrow). (B) PIP causes no zone of clearing on the PA14 spontaneous resistance mutant PA14-PIP^R. (C) PA14-PIP^R carrying the plasmid pUCP20 is resistant to PIP. (D) Introduction of the pilB complementation plasmid pUCP20-pilB into PA14-PIP^R restored sensitivity to PIP. Note: the size of the zones of clearing does not indicate relative susceptibilities, as the images in panels A and B were taken at a higher magnification to allow visualization of resistant colonies in panel A.