The phylogeny of environmental P. aeruginosa isolates. A maximum likelihood tree was generated from core genome alignments following removal of sequences under the influence of recombination. Isolates in red are exoU+, those in blue are exoS+, and the isolate in green is exoS−/exoU−. Reference strains PA14 (exoU+) and C-NN2 (clone c, exoS+) and three previously sequenced environmental isolates, M18 (Wu et al., 2011b), F9676 (Shi et al., 2015), and USDA-ARS-USMARC-41639 (Winsor et al., 2016), are shown in black.