FIG 3 .

Unguided genomic DNA transformations demonstrate that the mosaic mtrRCDE region causes increased azithromycin resistance. The 28Bl azithromycin-susceptible recipient strain was transformed with gDNA from mosaic mtr donor strains and selected on plates containing 0.38 to 1 µg/ml azithromycin. Genomic sequencing revealed the boundaries of recombined DNA that azithromycin-resistant transformants had inherited from mosaic donor strains (red bars) in the 28Bl background, as identified by SNP homology using the FA1090 reference genome as a scaffold. The only genomic region that was consistently inherited from donor strains in the transformant cell lines encompassed mtrRCDE for both the N. meningitidis (GCGS0276) and N. lactamica-like (GCGS0402 and GCGS0834) mtr mosaics. Average in vitro recombination tract lengths were 9.5 ± 1.4 kb for strain GCGS0276 (n = 4), 24.3 ± 3.6 kb for GCGS0834 (n = 9), and 31.4 ± 6.0 kb for GCGS0402 (n = 8). The locations of all DNA uptake sequences (DUS) (black circles), as well as the mtr locus (white box), are mapped in reference to the FA1090 strain.