Effect of fetal and adult bovine serum on pyocyanin production in Pseudomonas aeruginosa isolated from clinical and soil samples

Objectives Pyocyanin is a blue-greenish redox-active pigment, produced by Pseudomonas aeruginosa, with a wide range of biological and biotechnological applications. Pyocyanin biosynthesis is regulated by the quorum-sensing (QS) system in which the expression of QS genes and QS-controlled virulence genes may be affected by serum as a complex medium. In the current study, effects of adult bovine serum (ABS) and fetal bovine serum (FBS) on the production of pyocyanin were examined in order to develop it. Materials and Methods The presence of pyocyanin-producing specific genes and proteins in clinical and soil isolates of P. aeruginosa was confirmed using PCR and SDS-PAGE. Isolates were inoculated to media containing different concentrations of complement-active/-inactivated ABS or FBS and pyocyanin concentration was measured by spectrophotometry. Extracted pigment was characterized by using UV-Visible spectrophotometry. Titration of ABS antibodies against studied isolates was performed by the tube agglutination test. Results Adding ABS to P. aeruginosa culture medium decreased pyocyanin production compared to the control, while its production increased in FBS-containing media (113.21±2.581 vs. 55.26±0.827 μg.ml-1 and 126.80±2.036 vs. 30.56±0.382 μg.ml-1 of C11 and E8 pyocyanin concentration in the presence of 10% FBS vs. control, respectively). Conclusion In this study, due to the presence of inhibitors such as complement proteins and antibodies in ABS samples, the use of FBS devoid of antibodies was effective to increase pyocyanin production in studied isolates.