Bacteria belonging to the genus Paraburkholderia are capable of establishing symbiotic relationships with plants belonging to the Fabaceae (=Leguminosae) family and fixing the atmospheric nitrogen in specialized structures in the roots called nodules, in a process known as biological nitrogen fixation (BNF). In the nodulation and BNF processes several bacterial symbiotic genes are involved, but the relations between symbiotic, core genes and host specificity are still poorly studied and understood in Paraburkholderia. In this study, eight strains of nodulating nitrogen-fixing Paraburkholderia isolated in Brazil, together with described species and other reference strains were used to infer the relatedness between core (16S rDNA, recA) and symbiotic (nod, nif, fix) genes. The diversity of genes involved in the nodulation (nodAC) and nitrogen fixation (nifH) abilities was investigated. Only two groups, one containing three Paraburkholderia species symbionts of Mimosa, and another one with P. ribeironis strains presented similar phylogenetic patterns in the analysis of core and symbiotic genes. In three other groups events of horizontal gene transfer of symbiotic genes were detected. Paraburkholderia strains with available genomes were used in the complementary analysis of nifHDK and fixABC and confirmed well-defined phylogenetic positions of symbiotic genes. In all analyses of nod, nif and fix genes the strains were distributed into five clades with high bootstrap support, allowing the proposal of five symbiovars in nodulating nitrogen-fixing Paraburkholderia, designated as mimosae, africana, tropicalis, atlantica and piptadeniae. Phylogenetic inferences within each symbiovar are discussed.

属于副鞭毛菌属的细菌能够与属于豆科（豆科）的植物建立共生关系，并将大气中的氮固定在称为根瘤的根中的特殊结构中，这一过程称为生物固氮（BNF）。在结瘤和BNF过程中，涉及多个细菌共生基因，但是在Paraburkholderia中，共生，核心基因和宿主特异性之间的关系仍然缺乏研究和了解。在这项研究中，使用八种在巴西分离的结瘤固氮副枝假单胞菌菌株，描述的物种和其他参考菌株来推断核心（16S rDNA，recA）和共生（nod，nif，fix）基因。研究了参与结瘤（nodAC）和固氮（nifH）能力的基因的多样性。只有两组，其中一组含三个含羞草的巴拉伯霍尔德菌属共生体，另一组带有P. ribeironis菌株，在核心和共生基因分析中表现出相似的系统发育模式。在其他三个组中，检测到共生基因水平基因转移的事件。具有可用基因组的旁侧持球菌菌株用于nifHDK和fixABC的互补分析并确定了共生基因的明确系统发育位置。在对nod，nif和fix基因进行的所有分析中，将菌株分配到五个具有高引导带支持的进化枝中，从而提出了五个共生体在定氮固氮副毛虫中的提议，分别称为含羞草，非洲人，热带人，大西洋人和美人鱼。讨论了每个共生体内的系统发育推论。