Morphologies of ancestor and TMP-SMX-adapted endpoint isolates. The strain adapted in the bioreactor, MDA3349, demonstrated dramatic morphological diversity upon adaptation to TMP-SMX, while flask transfer-adapted strains MDA0897 and MDA3732 looked uniform after adaptation. In contrast to the endpoint isolates from serial-transfer experiments, bioreactor isolates were frequently sensitive to TMP-SMX, suggesting an ability to persist within the well-established biofilms of the bioreactor.