Although the microbial degradation of the six isomers of dimethylphenol has been extensively studied, the genetic and biochemical mechanisms of 2,6-DMP degradation remain unclear. This study identified the genes responsible for the initial step in the 2,6-DMP catabolic pathway in M. neoaurum B5-4.

Due to the extensive use of chloroacetanilide herbicides over the past 60 years, bacteria have evolved catabolic pathways to mineralize these compounds. In the upstream catabolic pathway, chloroacetanilide herbicides are transformed into the two common metabolites 2-methyl-6-ethylaniline (MEA) and 2,6-diethylaniline (DEA) through -dealkylation and amide hydrolysis. The pathway downstream of MEA is initiated by the hydroxylation of aromatic rings, followed by its conversion to a substrate for ring cleavage after several steps. Most of the key genes in the pathway have been identified. However, the genes involved in the initial hydroxylation step of MEA are still unknown. As a special aniline derivative, MEA cannot be transformed by the aniline dioxygenases that have been characterized. DE-13 can completely degrade MEA and use it as a sole carbon source for growth. In this work, an MEA degradation-deficient mutant of DE-13 was isolated. MEA catabolism genes were predicted through comparative genomic analysis. The results of genetic complementation and heterologous expression demonstrated that the products of and are responsible for the initial step of MEA degradation in DE-13. MeaXY is a two-component flavoprotein monooxygenase system that catalyzes the hydroxylation of MEA and DEA using NADH and flavin mononucleotide (FMN) as cofactors. Nuclear magnetic resonance (NMR) analysis confirmed that MeaXY hydroxylates MEA and DEA at the -position. Transcription of was enhanced remarkably upon induction of MEA or DEA in DE-13. Additionally, and were highly conserved among other MEA-degrading sphingomonads. This study fills a gap in our knowledge of the biochemical pathway that carries out mineralization of chloroacetanilide herbicides in sphingomonads. Much attention has been paid to the environmental fate of chloroacetanilide herbicides used for the past 60 years. Microbial degradation is considered an important mechanism in the degradation of these compounds. Bacterial degradation of chloroacetanilide herbicides has been investigated in many recent studies. Pure cultures or consortia able to mineralize these herbicides have been obtained. The catabolic pathway has been proposed, and most key genes involved have been identified. However, the genes responsible for the initiation step (from MEA to hydroxylated MEA or from DEA to hydroxylated DEA) of the downstream pathway have not been reported. The present study demonstrates that a two-component flavin-dependent monooxygenase system, MeaXY, catalyzes the -hydroxylation of MEA or DEA in sphingomonads. Therefore, this work finds a missing link in the biochemical pathway that carries out the mineralization of chloroacetanilide herbicides in sphingomonads. Additionally, the results expand our understanding of the degradation of a special kind of aniline derivative.

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A novel Gram-positive, fluoroglycofen-degrading bacterium, designated cmg86(T), was isolated from herbicide contaminated soil collected from Tongjing, Jiangsu province, China. Strain cmg86(T) was found to be aerobic, motile, endospore-forming rods. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain cmg86(T) belongs to the genus Lysinibacillus and showed the highest sequence similarity to Lysinibacillus meyeri DSM 25057(T) (97.9 %) and Lysinibacillus odysseyi KCTC 3961(T) (96.6 %). The cell-wall peptidoglycan type was determined to be A4α (L-Lys-D-Asp), which is consistent with the cell-wall characteristics of the genus Lysinibacillus. The predominant respiratory quinones were identified as menaquinone-7 (MK-7, 89.5 %) and meanaquinone-6 (MK-6, 8.9 %), and the major fatty acids were identified as iso-C15:0, anteiso-C15:0 and antesio-C17:0. The major polar lipids were found to be phosphatidylglycerol, diphosphatidylglycerol and phosphatidylethanolamine. The genomic DNA G+C content of strain cmg86(T) was determined to be 37.6 mol%. The results of this study support the conclusion that strain cmg86(T) represents a novel species of the genus Lysinibacillus for which the name and Lysinibacillus fluoroglycofenilyticus sp. nov. is proposed. The type strain is cmg86(T) (=KCTC 33183(T) = CCTCC AB 2013247(T)).