Proposal of Hymenobacter norwichensis sp. nov., classification of ‘Taxeobacter ocellatus’, ‘Taxeobacter gelupurpurascens’ and ‘Taxeobacter chitinovorans’ as Hymenobacter ocellatus sp. nov., Hymenobacter gelipurpurascens sp. nov. and Hymenobacter chitinivorans sp. nov., respectively, and emended description of the genus Hymenobacter Hirsch et al. 1999

Abstract

Two airborne bacterial isolates, NS/2 and NS/50T, were examined in order to determine their taxonomic position. Their almost complete 16S rRNA gene sequences shared 95.9 % similarity. Sequence comparisons demonstrated that their next relatives are species of the genus Hymenobacter (93.6–95.7 % similarity) and the strains ‘Taxeobacter chitinovorans’ Txc1T, ‘Taxeobacter gelupurpurascens’ Txg1T and ‘Taxeobacter ocellatus’ Myx 2105T (90.5–96.4 %). Phylogenetic calculations indicated that these five strains together with the three recognized Hymenobacter species form a separate line of descent within the family ‘Flexibacteraceae’. Isolates NS/2 and NS/50T, as well as ‘Taxeobacter chitinovorans’ Txc1T, ‘Taxeobacter gelupurpurascens’ Txg1T and ‘Taxeobacter ocellatus’ Myx 2105T, possessed the characteristics of the genus Hymenobacter, the quinone system menaquinone MK-7 and a polyamine pattern with the major polyamine being sym-homospermidine. Each of the five strains had complex, unique polar lipid profiles, with phosphatidylethanolamine and several unknown aminophospho-, amino-, phospho-, glyco- and polar lipids of which several compounds were also found in established Hymenobacter species. All the strains studied possessed fatty acids characteristic of Hymenobacter species, including major acids iso-C15 : 0, anteiso-C15 : 0, C16 : 1 ω5c, summed feature 3 (C16 : 1 ω7c/iso-C15 : 0 2-OH) and summed feature 4 (iso-C17 : 1 I/anteiso-C17 : 1 B). The five strains could be distinguished from each other and from the three established species of the genus Hymenobacter based on relatively low 16S rRNA gene sequence similarities (<97 %), unique polar lipids and differing fatty acid profiles and physiological characteristics. In conclusion, the description of four novel species of the genus Hymenobacter appears to be justified, for which the names Hymenobacter norwichensis sp. nov. (type strain NS/50T=LMG 21876T=DSM 15439T), Hymenobacter chitinivorans sp. nov. (type strain Txc1T=LMG 21951T=DSM 11115T), Hymenobacter gelipurpurascens sp. nov. (type strain Txg1T=LMG 21873T=DSM 11116T) and Hymenobacter ocellatus sp. nov. (type strain Myx 2105T=Txo1T=LMG 21873T=DSM 11117T) are proposed. For strain NS/2, a description only is provided without proposal of a name because its status as a novel species was not demonstrated unambiguously.