The para-Nitrophenol Catabolic Gene Cluster is Responsible for 2-Chloro-4-nitrophenol Degradation in Burkholderia sp. Strain SJ98

Min J, Zhang JJ, Zhou NY. 

Appl Environ Microbiol. 2014 Aug 1. pii: AEM.02093-14.

Abstract

　　Burkholderia sp. strain SJ98 (DSM 23195) utilizes 2-chloro-4-nitrophenol (2C4NP) or para-nitrophenol (PNP) as a sole source of carbon and energy. Here, by genetic and biochemical analyses, a 2C4NP catabolic pathway different from those of all other 2C4NP utilizers was identified with chloro-1,4-benzoquinone (CBQ) as an intermediate. Reverse transcription PCR analysis showed that all the pnp genes in pnpABA1CDEF cluster were located in a single operon, significantly different from the genetic organization of all other previously reported PNP degradation gene clusters in which the structural genes were located in three different operons. All the Pnp proteins were purified to homogeneity as His-tagged proteins. PnpA, a PNP 4-monooxygenase, was found to be able to catalyze the monooxygenation of 2C4NP to CBQ. PnpB, a 1,4-benzoquinone (BQ) reductase, has the ability to catalyze the reduction of CBQ to chlorohydroquinone (CHQ). Moreover, PnpB is also able to enhance PnpA activity in vitro in the converstion of 2C4NP to CBQ. Genetic analyses indicated that pnpA plays an essential role in both 2C4NP and PNP degradations by gene knockout and complementation. In addition to be responsible for the lower pathway of PNP catabolism, PnpCD, PnpE and PnpF were also found to be likely involved in that of 2C4NP catabolism. These results indicated that the catabolism of 2C4NP and PNP share the same gene cluster in strain SJ98. The findings fill a gap in our understanding of the microbial degradation of 2C4NP at molecular and biochemical levels. 

http://aem.asm.org/content/early/2014/07/28/AEM.02093-14.short