Aromatoleum gen. nov., a novel genus accommodating the phylogenetic lineage including Azoarcus evansii and related species, and proposal of Aromatoleum aromaticum sp. nov., Aromatoleum petrolei sp. nov., Aromatoleum bremense sp. nov., Aromatoleum toluolicum sp. nov. and Aromatoleum diolicum sp. nov.

Comparative 16S rRNA gene sequence analysis and major physiological differences indicate two distinct sublineages within the genus Azoarcus: the Azoarcus evansii lineage, comprising Azoarcus evansii (type strain KB740(T)=DSM 6898(T)=CIP 109473(T)=NBRC 107771(T)), Azoarcus buckelii (type strain U120(T)=DSM 14744(T)=LMG 26916(T)), Azoarcus anaerobius (type strain LuFRes1(T)=DSM 12081(T)=LMG 30943(T)), Azoarcus tolulyticus (type strain Tol-4(T)=ATCC 51758(T)=CIP 109470(T)), Azoarcus toluvorans (type strain Td21(T)=ATCC 700604(T)=DSM 15124(T)) and Azoarcus toluclasticus (type strain MF63(T)=ATCC 700605(T)), and the Azoarcus indigens lineage, comprising Azoarcus indigens (type strain VB32(T)=ATCC 51398(T)=LMG 9092(T)), Azoarcus communis (type strain SWub3(T)=ATCC 51397(T)=LMG 9095(T)) and Azoarcus olearius (type strain DQS-4(T)=BCRC 80407(T)=KCTC 23918(T)=LMG 26893(T)). Az. evansii lineage members have remarkable anaerobic degradation capacities encompassing a multitude of alkylbenzenes, aromatic compounds and monoterpenes, often involving novel biochemical reactions. In contrast, Az. indigens lineage members are diazotrophic endophytes lacking these catabolic capacities. It is proposed that species of the Az. evansii lineage should be classified in a novel genus, Aromatoleum gen. nov. Finally, based on the literature and new growth, DNA-DNA hybridization and proteomic data, the following five new species are proposed: Aromatoleum aromaticum sp. nov. (type strain EbN1(T)=DSM 19018(T)=LMG 30748(T) and strain pCyN1=DSM 19016=LMG 31004), Aromatoleum petrolei sp. nov. (type strain ToN1(T)=DSM 19019(T)=LMG 30746(T)), Aromatoleumbremense sp. nov. (type strain PbN1(T)=DSM 19017(T)=LMG 31005(T)), Aromatoleum toluolicum sp. nov. (type strain T-T=DSM 19020(T)=LMG 30751(T)) and Aromatoleum diolicum sp. nov. (type strain 22Lin(T)=DSM 15408(T)=LMG 30750(T)).