Bandi C, Damiani G, Magrassi L, Grigolo A, Fani R, Sacchi L
Istituto di Patologia Generale Veterinaria, Università di Milano, Italy.
Proc Biol Sci. 1994 Jul 22;257(1348):43-8. doi: 10.1098/rspb.1994.0092.
Animal cells are the sole habitat for a variety of bacteria. Molecular sequence data have been used to position a number of these intracellular microorganisms in the overall scheme of eubacterial evolution. Most of them have been classified as proteobacteria or chlamydiae. Here we present molecular evidence placing an intracellular symbiont among the flavobacteria-bacteroides. This microorganism inhabits specialized cells in the cockroach fat body and has been described as a mutualistic endosymbiont of uncertain phylogenetic position. The small subunit ribosomal DNA of these bacteria was analysed after polymerase chain reaction amplification to investigate their phylogeny. The endosymbionts of five species of cockroaches were found to make up a coherent group with no close relatives within the eubacterial phylum defined by the flavobacteria. In addition, the relationships among the endosymbionts, as revealed by DNA sequence data, appeared to be congruent with the host taxonomic relationships. Based on the host fossil record, a tentative calibration of the nucleotide substitution rate for the cockroach flavobacteria gave results congruent with those obtained for the aphid endosymbiotic proteobacteria.
动物细胞是多种细菌的唯一栖息地。分子序列数据已被用于在真细菌进化的总体框架中确定许多这些细胞内微生物的位置。它们中的大多数已被归类为变形菌或衣原体。在这里，我们提供了分子证据，表明一种细胞内共生体属于黄杆菌-拟杆菌类群。这种微生物栖息在蟑螂脂肪体的特化细胞中，被描述为一种系统发育位置不确定的互利共生内共生体。在聚合酶链反应扩增后，对这些细菌的小亚基核糖体DNA进行了分析，以研究它们的系统发育。发现五种蟑螂的内共生体在由黄杆菌定义的真细菌门内组成了一个连贯的类群，没有近亲。此外，DNA序列数据揭示的内共生体之间的关系似乎与宿主分类关系一致。基于宿主化石记录，对蟑螂黄杆菌核苷酸替代率的初步校准结果与蚜虫内共生变形菌的结果一致。
