猪附红细胞体16S rRNA基因的序列测定和系统进化分析

从确诊为猪附红细胞体感染的猪场，无菌采集血样，抽提猪附红细胞体基因组DNA，采用真细菌的通用引物进行16S rRNA基因扩增，对扩增产物进行克隆和测序。从3个地理位置不同的猪场均成功地扩增出长度为1469bp的核苷酸序列。系统进化分析表明，3个猪场样品所测序列一致性达99．52％以上，具有相同的基因型，但与国外报道的猪附红细胞体Illinois株同源性为95％，属于同一基因群，但基因型不同；所有种类的附红细胞体和血巴尔通氏体组成同一进化分支，这类血营养菌与支原体科，支原体属的病原最靠近(75％)，而与立克次氏体目的病原较远(70％)。上述研究证实，广东所流行的猪附红细胞体是一种新基因型的猪附红细胞体，建议命名为猪附红细胞体广东株型；为反映进化关系，猪附红细胞体和其它血营养菌应划归于支原体科的支原体属。

Sequencing and Phylogenetic Analysis of the 16S rRNA Gene of Eperythrozoon suis

The Eperythrozoon suis genomic DNA was extracted from blood samples with Eperythrozoon infection based on the light and electron microscopic examinations. The 16S rRNA gene was amplified by using the universal eubacterial primers. The PCR product was cloned and sequenced. A sequence of 1 469 base-pair(bp) was obtained from each of the three naturally infected pigs at the different pig farm. Each of the three sequences was compared to that derived from GenBank using BLASTn, and the closest sequence was 16S rRNA gene of E. suis Illinois strain, with a similarity of 95%. These findings suggested that the E.suis isolated from pigs in Guangdong, China is a new genetype E. suis. The phylogenetic analysis based on the 16S rRNA genes sequences of E.suis Guangdong strain and other related organisms, including Eperythrozoon and Haemobartonella, some species of Mycoplasmatales and Rickettsiales in GenBank database, showed that all species in Eperythrozoon and haemobartonella formed a separate and distinct phylogenetic branch, these haemotrophic bacteria were more closely related to Mycoplasma spp.in Mycoplasmatales (75%)than to Anaplasma, Bartonella and Ehrlichia spp in Rickettsiales (70%). Our results indicated that Eperythrozoon and Haemobartonella genera should be reclassified in Mycoplasma genus of Mycoplasmatales to reflect their actual phylogenetic relations.