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Master thesis

Microbial adaptations towards utilisation of the explosive RDX in soil

Abstract : The extensive use of the explosive compound hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) has resulted in the contamination of land and groundwater. Its low sorption coefficient makes RDX a priority since it has been classified as a class C possible human carcinogen. In almost 60 years, many bacteria belonging to the Actinomycetales have adapted to degrade RDX such as Rhodococcus rhodochrous 11Y, Microbacterium sp. MA1, Williamsia sp. EG1 and Gordonia sp. KTR9. The xplA and xplB genes which code for a unique cytochrome P450 fused to a flavodoxin and its reductase catalyse the reductive denitration and subsequently ring cleavage of RDX. The xplA/xplB genes are present in all of these isolates and are highly conserved. Nevertheless, single amino acid mutations are the reason of the inactivity of XplB in MA1 and KTR9. A surprising fusion of XplB to a glutamine synthetase in KTR9 seems to form a massive oligomer which could be part of a new regulation pathway of xplA. Homologous xplA sequences recently released were found from Gordonia terrae strain NBRC100016 and Gordonia isoprenivorans. Gt-XplA from G. terrae is the second cytochrome P450 fused to a flavodoxin to be discovered. Moreover it is surrounded by homologues xplA cluster’s genes. Site directed mutagenesis of key amino acids from the active site allowed these enzymes the ability to degrade RDX, providing insights of the origin of xplA/xplB.
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Master thesis
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Submitted on : Thursday, April 19, 2018 - 9:48:14 AM
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  • HAL Id : hal-01770484, version 1



Nicolas Grosjean. Microbial adaptations towards utilisation of the explosive RDX in soil. Microbiology and Parasitology. 2015. ⟨hal-01770484⟩



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