Growth curves of strains PAK, PAK(aph), and PAK(hpaA) as well as those of strain PAK(hpaA) containing pWC011 (hpaA clone) or pWC014 (control) in M63 medium supplemented with 10 mM 4-HPA as the sole carbon source or left untreated. Group A includes strains PAK, PAK(aph), and PAK(hpaA)/pWC011 in M63 medium with 4-HPA. Group B includes strains PAK, PAK(aph), and PAK(hpaA)/pWC011 in M63 medium without 4-HPA and also strains PAK(hpaA) and PAK(hpaA)/WC014 in M63 medium with and without 4-HPA.