Biodegradation of 2-bromonitrobenzene by Pseudomonas stutzeri ZWLR2-1

Halonitrobenzenes are highly harmful to human health and the environment. Among them, chloronitrobenzenes have been reported to be degraded by several bacterial strains. However, till date, the biodegradation of bromonitrobenzenes has not been reported for any pure bacterial culture. In this study, 2-bromonitrobenzene was found to be utilized by the 2-chloronitrobenzene utilizer Pseudomonas stutzeri ZWLR2-1 as the sole source of carbon, nitrogen and energy for growth, with nitrite release. The nitroaromatic dioxygenase CnbAaAbAcAd from strain ZWLR2-1 converted 2-bromonitrobenzene to 3-bromocatechol with concomitant nitrite release. CnbC exhibited 3-bromocatechol 1,2-dioxygenase activity. The identity of 3-bromocatechol was confirmed by Liquid Chromatograph-Mass Spectrometer (LC-MS), in comparison with authentic 3-bromocatechol. These results demonstrated that the cnb cluster of Pseudomonas stutzeri ZWLR2-1 is responsible for the biodegradation of both 2-chloronitrobenzene and 2-bromonitrobenzene, providing yet another example of a bacterium having rapidly evolved a pathway to utilize multiple xenobiotics.