AaPAL expression in different growth conditions of A. actinomycetemcomitans. Strains D7S (wild-type, lane 1), D7SS (spontaneous smooth-colony variant of D7S, lane 2), and D7SS-p (pal-deficient mutant of D7SS, lane 3) were cultured in various nutritional and atmospheric conditions (for details, see Materials and Methods). Bacterial whole cell protein preparations (10 μg/well) were subjected to immunoblot analysis with anti-AaPAL peptide antiserum. The OMP preparations from the strains D7SS (lane 4) and D7SS-p (lane 5) were used as a positive and a negative control, respectively. CO2: CO2-enriched air (5%); BA: blood agar; TSA: trypticase soy agar.