Zhang_2010_World.J.Microbiol.Biotechnol_26_665

A novel degradation pathway of chloroaniline in Diaphorobacter sp. PCA039 entails initial hydroxylation. A novel gene cluster (pca), involved in the degradation of p-chloroaniline, was identified from Diaphorobacter sp. PCA039 capable of utilizing p-chloroaniline as sole carbon, nitrogen and energy source for growth. There were 29 ORFs in the pca cluster, in the order of pcaTRKLMNOPR D C I U R D C U EFGXJHYWZI I QS. Based on sequence analysis, they were putatively identified as encoding a multicomponent phenol-hydroxylating oxygenase (pcaKLMNOP), two extradiol ring-cleavage dioxygenases, transcriptional regulatory proteins, enzymes mediating chlorocatechol degradation, and transportation functions. The genes pcaKLMNOP exhibited significant sequence identity (94%) to those of phenol hydroxylases (PH) from other bacteria, inferring that they might encode a multicomponent PH. This PH activity was also functionally characterized with the recombinant strain E. coli TOP10-S201 showing only PH activity, indicating that the degradation of p-chloroaniline by strain PCA039 was initiated by hydroxylation instead of normal dioxygenation. The other nineteen genes, pcaR D C I U R D C U EFGXJHYWZI I , encode for further degradation of p-chloroaniline to intermediates of the TCA-cycle and transposases. RT-PCR revealed that the hydrolytic (pcaF) and dehydrogenetic pathways (pcaE, pcaH), the two degrading branches, are both necessary for complete degradation of aniline, p-chloroaniline, phenol and also 4-aminophenol; and of the two C23O sets, PcaRDCU and PcaRDCU, PcaC1 is produced in the degradation of above four substrates, while PcaC2 is only expressed in p-chloroaniline degradation, suggesting that both C23O sets are needed for complete degradation of p-chloroaniline.