Catabolism of the groundwater micropollutant 2,6-dichlorobenzamide beyond 2,6-dichlorobenzoate is plasmid encoded in Aminobacter sp MSH1

T'Syen, J.; Raes, B.; Horemans, B.; Tassoni, R.; Leroy, B.; Lood, C.; ... ; Springael, D. (2018)

Article / Letter to editor

Aminobacter sp. MSH1 uses the groundwater micropollutant 2,6-dichlorobenzamide (BAM) as sole source of carbon and energy. In the first step, MSH1 converts BAM to 2,6-dichlorobenzoic acid (2,6-DCBA) by means of the BbdA amidase encoded on the IncP-1 beta plasmid pBAM1. Information about the genes and degradation steps involved in 2,6-DCBA metabolism in MSH1 or any other organism is currently lacking. Here, we show that the genes for 2,6-DCBA degradation in strain MSH1 reside on a second catabolic plasmid in MSH1, designated as pBAM2. The complete sequence of pBAM2 was determined revealing that it is a 53.9 kb repABC family plasmid. The 2,6-DCBA catabolic genes on pBAM2 are organized in two main clusters bordered by IS elements and integrase genes and encode putative functions like Rieske mono-/dioxygenase, meta-cleavage dioxygenase, and reductive dehalogenases. The putative mono-oxygenase encoded by the bbdD gene was shown to convert 2,6-DCBA to 3-hydroxy-2,6-dichlorobenzoate (3-OH-2,6-DCBA). 3-OH-DCBA was degraded by wild-type MSH1 and not by a pBAM2-free MSH1 variant indicating that it is a likely intermediate in the pBAM2-encoded DCBA catabolic pathway. Based on the activity of BbdD and the putative functions of the other catabolic genes on pBAM2, a metabolic pathway for BAM/2,6-DCBA in strain MSH1 was suggested.

• All authors: T'Syen, J.; Raes, B.; Horemans, B.; Tassoni, R.; Leroy, B.; Lood, C.; Noort, V. van; Lavigne, R.; Wattiez, R.; Kohler, H.P.E.; Springael, D.
• Date: 2018-09-01
• Volume: 102
• Pages: 7963 - 7979
• DOI: doi:10.1007/s00253-018-9189-9