Oligoflexus tunisiensis gen. nov., sp. nov., a Gram-negative, aerobic, filamentous bacterium of a novel proteobacterial lineage, and description of Oligoflexaceae fam. nov., Oligoflexales ord. nov. and Oligoflexia classis nov.

<jats:p>A phylogenetically novel proteobacterium, strain Shr3<jats:sup>T</jats:sup>, was isolated from sand gravels collected from the eastern margin of the Sahara Desert. The isolation strategy targeted bacteria filterable through 0.2-µm-pore-size filters. Strain Shr3<jats:sup>T</jats:sup> was determined to be a Gram-negative, aerobic, non-motile, filamentous bacterium. Oxidase and catalase reactions were positive. Strain Shr3<jats:sup>T</jats:sup> showed growth on R2A medium, but poor or no growth on nutrient agar, trypticase soy agar and standard method agar. The major isoprenoid quinone was menaquinone-7. The dominant cellular fatty acids detected were C<jats:sub>16 : 1</jats:sub>ω5<jats:italic>c</jats:italic> and C<jats:sub>16 : 0</jats:sub>, and the primary hydroxy acid present was C<jats:sub>12 : 0</jats:sub> 3-OH. The DNA G+C content was 54.0 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain Shr3<jats:sup>T</jats:sup> was affiliated with an uncultivated lineage of the phylum <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="phylum" xlink:type="simple"> <jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.808" xlink:type="simple"> <jats:italic>Proteobacteria</jats:italic> </jats:ext-link> </jats:named-content>; the nearest known type strain, with 83 % sequence similarity, was <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="species" xlink:type="simple"> <jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.3522" xlink:type="simple"> <jats:italic>Desulfomicrobium orale</jats:italic> </jats:ext-link> </jats:named-content> DSM 12838<jats:sup>T</jats:sup> in the class <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="class" xlink:type="simple"> <jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.3456" xlink:type="simple"> <jats:italic>Deltaproteobacteria</jats:italic> </jats:ext-link> </jats:named-content>. The isolate and closely related environmental clones formed a novel class-level clade in the phylum <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="phylum" xlink:type="simple"> <jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.808" xlink:type="simple"> <jats:italic>Proteobacteria</jats:italic> </jats:ext-link> </jats:named-content> with high bootstrap support (96–99 %). Based on these results, the novel class <jats:italic>Oligoflexia</jats:italic> classis nov. in the phylum <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="phylum" xlink:type="simple"> <jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.808" xlink:type="simple"> <jats:italic>Proteobacteria</jats:italic> </jats:ext-link> </jats:named-content> and the novel genus and species <jats:italic>Oligoflexus tunisiensis</jats:italic> gen. nov., sp. nov. are proposed for strain Shr3<jats:sup>T</jats:sup>, the first cultivated representative of the <jats:italic>Oligoflexia</jats:italic>. The type strain of <jats:italic>Oligoflexus tunisiensis</jats:italic> is Shr3<jats:sup>T</jats:sup> ( = JCM 16864<jats:sup>T</jats:sup> = NCIMB 14846<jats:sup>T</jats:sup>). We also propose the subordinate taxa <jats:italic>Oligoflexales</jats:italic> ord. nov. and <jats:italic>Oligoflexaceae</jats:italic> fam. nov. in the class <jats:italic>Oligoflexia</jats:italic>.</jats:p>