Picolinic acid (PA) is a typical mono-carboxylated pyridine derivative produced by human/animals or microorganisms which could be served as nutrients for bacteria. Most Bordetella strains are pathogens causing pertussis or respiratory disease in humans and/or various animals. Previous studies indicated that Bordetella strains harbor the PA degradation pic gene cluster. However, the degradation of PA by Bordetella strains remains unknown. In this study, a reference strain of genus Bordetella, B. bronchiseptica RB50, was investigated. The organization of pic gene cluster of strain RB50 was found to be similar with that of Alcaligenes faecalis, in which the sequence similarities of each Pic proteins are between 60% to 80% except for PicB2 (47% similarity). The 3,6-dihydroxypicolinic acid (3,6DHPA) decarboxylase gene (BB0271, designated as picCRB50) of strain RB50 was synthesized and over-expressed in E. coli BL21(DE3). The PicCRB50 showed 75% amino acid similarities against known PicC from Alcaligenes faecalis. The purified PicCRB50 can efficiently transform 3,6DHPA to 2,5-dihydroxypyridine. The PicCRB50 exhibits optimal activities at pH 7.0, 35 °C, and the Km and kcat values of PicCRB50 for 3,6DHPA were 20.41 ± 2.60 μM and 7.61 ± 0.53 S-1, respectively. The present study provided new insights into the biodegradation of PA by pathogens of Bordetella spp.
Keywords: Bordetella bronchiseptica RB50; biodegradation; decarboxylase; pathogen; picolinic acid.