Strains L10T, L108 and CIP I-2052 were originally obtained from Me tert-Bu ether (MTBE)-contaminated groundwater and from a wastewater treatment plant, resp. All share the ability to grow on tert-butanol, an intermediate of MTBE degrdn. Cells are strictly aerobic, motile by a polar flagellum and exhibit strong pili formation. Poly b-hydroxybutyrate (PHB) granules are formed. The DNA G + C content is 69-70.5 mol% and the main ubiquinone is Q-8. The major cellular fatty acids are 16:1 cis-9 and 16:0 and the only hydroxy fatty acid is 10:0 3-OH. The major phospholipids are phosphatidylethanolamine (PE) 16:1/16:1 and phosphatidylglycerol 16:0/16:1. A significant amt. of PE 17:0/16:1 is present. The 16S rRNA gene sequences of these strains are almost identical and form a sep. line of descent in the Rubrivivax-Roseateles-Leptothrix-Ideonella-Aquabacterium branch of the Betaproteobacteria with 97 % similarity to 16S rRNA genes of the type strains of Rubrivivax gelatinosus, Leptothrix mobilis and Ideonella dechloratans. However, physiol. properties, DNA-DNA relatedness values and the phospholipid and cellular fatty acid profiles distinguish the novel isolates from the three closely related genera. Therefore, it is concluded that strains L10T, L108 and CIP I-2052 represent a new genus and novel species for which the name Aquincola tertiaricarbonis gen. nov., sp. nov., is proposed. The type strain is strain L10T (= DSM 18512T = CIP 109243T).