Summary We morphologically and molecularly characterized segmented filamentous bacteria (SFB) associated with Rhigonema sp. nematodes in millipede hindguts. Seventy-three Riukiaria sp. millipedes were collected from a broad-leaf forest in Japan, and nematodes were excised from the millipede’s hindguts. The occurrence rate of SFB associated with nematodes was 24 % (10/41) for males, 47 % (14/30) for females, and 100 % (2/2) for juveniles. Genomic DNA was extracted from four SFB-rich nematode heads, and we obtained 40 bacterial clones via analysis of nearly full-length 16S rDNA gene sequences. At the phylum level, Firmicutes, Proteobacteria, and Verrucomicrobia accounted for 55 %, 40 %, and 5 % of SFB, respectively. In Firmicutes, Clostridiaceae (28 %) and Lachnospiraceae (15 %) were the dominant groups. Our sequences were divided into seven and three subclades between Firmicutes and Proteobacteria in the phylogenetic tree. In the Firmicutes clade, eight sequences were classified as Lachnospiraceae with a bootstrap value >83 %. A phylogenetic tree involving known uncultured Lachnospiraceae sequences characterized the phylogenetic position of SFB associated with nematodes. Our results suggest that the association of SFB with nematode bodies was probably incidental and that SFB are not always present in millipede hindguts. Our bacterial groups corresponded to those of arthropod hindgut, and SFB associated with nematodes were inferred to belong to Lachnospiraceae. Because the Lachnospiraceae sequences obtained in this study showed specific lineages that differed from all the known deposited sequence data, these groups may be unique to Riukiaria sp.

中文翻译：

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与Rhigonema sp.相关的分段丝状细菌的首次报告。（线虫科：Rhigonematidae）栖息在 Riukiaria sp. 的后肠。（双足纲：木虱科）

总结我们从形态学和分子学上表征了与 Rhagonema sp. 相关的分段丝状细菌 (SFB)。千足虫后肠中的线虫。七十三 Riukiaria sp。从日本的阔叶林中收集千足虫，从千足虫的后肠中切除线虫。与线虫相关的SFB发生率为雄性24%（10/41），雌性47%（14/30），幼虫100%（2/2）。从四个富含 SFB 的线虫头中提取基因组 DNA，我们通过分析几乎全长的 16S rDNA 基因序列获得了 40 个细菌克隆。在门水平上，厚壁菌门、变形菌门和疣微菌门分别占 SFB 的 55%、40% 和 5%。在厚壁菌门中，梭菌科 (28%) 和毛螺菌科 (15%) 是优势群。我们的序列在系统发育树中分为厚壁菌门和变形菌门之间的七个和三个亚分支。在厚壁菌门进化枝中，8 个序列被归类为毛螺菌科，引导值 >83%。涉及已知未培养的毛螺科序列的系统发育树表征了与线虫相关的 SFB 的系统发育位置。我们的结果表明 SFB 与线虫体的关联可能是偶然的，并且 SFB 并不总是存在于千足虫后肠中。我们的细菌群对应于节肢动物后肠的细菌群，与线虫相关的 SFB 被推断为属于​​毛螺科。由于本研究中获得的毛螺菌科序列显示出与所有已知的沉积序列数据不同的特定谱系，