Identification of A Ring-Hydroxylating Dioxygenases Capable of Anthracene and Benz[a]anthracene Oxidization from <b><i>Rhodococcus</i></b> sp. P14

Nowadays, contamination of soil and marine sediments by polycyclic aromatic hydrocarbons (PAHs) has become a serious problem all over the world. <i>Rhodococcus</i> sp. P14 was isolated from sediments with crude oil contaminate and showed degradation ability on various PAHs. The genome of <i>Rhodococcus</i> sp. P14 was sequenced. A gene cluster encoding a ring-hydroxylating dioxygenase Baa related to PAH degradation was identified by bioinformatics. The expression level of gene <i>baaA</i> was increased when P14 was cultured with anthracene, pyrene, phenanthrene, or benz[a]­anthracene as the single carbon source. The recombinant protein Baa was overexpressed in <i>E. coli</i> BL21 (DE3). Further investigations on the recombinant protein Baa in <i>E. coli</i> demonstrated that it was able to oxidize anthracene and benz [a]anthracene, resulting in 9,10-dihydroxyanthracene and 7, 12-dihydroxybenz[a]anthracene as metabolites, respectively. These results indicate that Baa plays an important role in PAH degradation in <i>Rhodococcus</i> sp. P14 and Baa has potential application in the bioremediation of PAHs in the contaminated environment.