Characterization of filamentous Eikelboom type 021N bacteria and description of Thiothrix disciformis sp. nov. and Thiothrix flexilis sp. nov.

The phenotypic and genotypic characteristics of 15 strains of Eikelboom type 021 N bacteria isolated from wastewater treatment plants were investigated. The strains shared many characters with Thiothrix species. However, the Eikelboom type 021N bacteria had only 88.3-92.0% 16S rDNA sequence similarity to members of the Thiothrix nivea group, including T. nivea, 'Thiothrix ramosa', Thiothrix unzii and Thiothrix fructosivorans, and were differentiated from them in sugar utilization and other properties, suggesting that the Eikelboom type 021N bacteria belong to species distinct from the T. nivea group. The 15 Eikelboom type 021N bacteria that were investigated were divided into three distinct groups (I to III) on the basis of their genotypic and phenotypic characteristics. The creation of two novel species is proposed, Thiothrix disciformis sp. nov. for the group I strains (type strain B3-1T = JCM 11364T = DSM 14473T) and Thiothrix flexilis sp. nov. for the group III strains (type strain EJ2M-BT = JCM 11135T = DSM 14609T). Thiothrix eikelboomii AP3T was included in group II and shared many characters with the other group II strains. The inclusion of all group II strains within the species T. eikelboomii is proposed,together with emendation of the description of T. eikelboomii.