title: The thuEFGKAB operon of rhizobia and agrobacterium tumefaciens codes for transport of trehalose, maltitol, and isomers of sucrose and their assimilation through the formation of their 3-keto derivatives.
abstract: The thu operon (thuEFGKAB) in Sinorhizobium meliloti codes for transport and utilization functions of the disaccharide trehalose. Sequenced genomes of members of the Rhizobiaceae reveal that some rhizobia and Agrobacterium possess the entire thu operon in similar organizations and that Mesorhizobium loti MAFF303099 lacks the transport (thuEFGK) genes. In this study, we show that this operon is dedicated to the transport and assimilation of maltitol and isomers of sucrose (leucrose, palatinose, and trehalulose) in addition to trehalulose, not only in S. meliloti but also in Agrobacterium tumefaciens. By using genetic complementation, we show that the thuAB genes of S. meliloti, M. loti, and A. tumefaciens are functionally equivalent. Further, we provide both genetic and biochemical evidence to show that these bacteria assimilate these disaccharides by converting them to their respective 3-keto derivatives and that the thuAB genes code for this ketodisaccharide-forming enzyme(s). Formation of 3-ketotrehalose in real time in live S. meliloti is shown through Raman spectroscopy. The presence of an additional ketodisaccharide-forming pathway(s) in A. tumefaciens is also indicated. To our knowledge, this is the first report to identify the genes that code for the conversion of disaccharides to their 3-ketodisaccharide derivatives in any organism.
authors.affiliation: Institute for Arctic and Marine Biology, University of Tromsø, Tromsø, Norway.
authors.forename: Osei Yaw
authors.initials: OY
authors.lastname: Ampomah
authors.forename: Anna
authors.initials: A
authors.lastname: Avetisyan
authors.forename: Espen
authors.initials: E
authors.lastname: Hansen
authors.forename: Johan
authors.initials: J
authors.lastname: Svenson
authors.forename: Thomas
authors.initials: T
authors.lastname: Huser
authors.forename: John Beck
authors.initials: JB
authors.lastname: Jensen
authors.forename: T V
authors.initials: TV
authors.lastname: Bhuvaneswari
mesh_terms: D016960:Agrobacterium tumefaciens / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D001711:Biotransformation; D005816:Genetic Complementation Test; D008320:Maltose / Q000031:analogs & derivatives* / Q000378:metabolism; D053858:Metabolic Networks and Pathways / Q000235:genetics; D009876:Operon; D016962:Sinorhizobium meliloti / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013059:Spectrum Analysis, Raman; D013395:Sucrose / Q000378:metabolism*; D013402:Sugar Alcohols / Q000378:metabolism*; D014199:Trehalose / Q000378:metabolism*
chemical_list: D013402:Sugar Alcohols; D013395:Sucrose; D008320:Maltose; D014199:Trehalose; C010745:maltitol