S93: Characterization of the xplA genomic island in RDX degrading bacteria

The extensive use of the royal demolition explosive RDX (Hexahydro-1, 3, 5-trinitro-1, 3, 5-triazine) in military operations has resulted in heavy contamination of vast areas of land.  RDX is toxic and classified as a potential human carcinogen. The widespread pollution with RDX is of concern as RDX is recalcitrant to degradation and highly mobile in the soil contaminating drinking water supplies.  Rhodococcus rhodochrous 11Y was isolated for its ability to use RDX as a sole source of nitrogen degrading RDX to less toxic compounds. Since the first discovery of R. rhodochrous 11Y, a number of bacteria from different geographical regions belonging to the Corynebacterineae were isolated for their ability to degrade RDX. Interestingly, all these bacteria have in common a highly conserved genomic island harbouring xplA and B, spanning a region of 15 kb.  However, the occurrence of these bacteria in contaminated soils is not sufficient for remediation purposes, possibly caused by low activity or insufficient numbers. In order to understand the regulation of the gene cluster and improve bacteria for bioremediation, we characterized the RDX degrading genomic island knocking out target genes in R.  rhodochrous 11Y.  So far our results have shown that the RDX degrading capacity is lost and reduced in xplA and xplB knock out mutants, respectively.  Whereas, knocking out the genes encoding a permease AroP and a putative regulatory protein MarR, located upstream of xplA, has not shown any significant effects on RDX degradation. Studies on other target genes are currently ongoing.