Embrapa Soja, C.P. 231, 86001-970 Londrina, Paraná, Brazil; Departamento de Microbiologia, Universidade Estadual de Londrina, C.P. 10011, 86057-970 Londrina, Paraná, Brazil; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, SBN, Quadra 2, Bloco L, Lote 06, Edifício Capes, 70.040-020 Brasília, Distrito Federal, Brazil.
Embrapa Soja, C.P. 231, 86001-970 Londrina, Paraná, Brazil; Conselho Nacional de Desenvolvimento Científico e Tecnológico, SHIS QI 1 Conjunto B, Blocos A, B, C e D, Lago Sul, 71605-001 Brasília, Distrito Federal, Brazil.
Syst Appl Microbiol. 2020 Nov;43(6):126151. doi: 10.1016/j.syapm.2020.126151. Epub 2020 Oct 14.
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 Paraburkholderia 属的细菌能够与豆科 (= Leguminosae)家族的植物建立共生关系，并在被称为根瘤的专门结构中固定大气氮，这一过程称为生物固氮 (BNF)。在结瘤和 BNF 过程中，涉及到几个细菌共生基因，但 Paraburkholderia 中共生、核心基因和宿主特异性之间的关系仍研究和理解甚少。在这项研究中，从巴西分离出的 8 株固氮结瘤 Paraburkholderia 菌株与描述的物种和其他参考菌株一起，用于推断核心（16S rDNA、recA）和共生（nod、nif、fix）基因之间的亲缘关系。调查了参与结瘤（nodAC）和固氮（nifH）能力的基因多样性。只有两个组，一组包含三个含羞草共生的 Paraburkholderia 物种，另一组含有 P. ribeironis 菌株，在核心和共生基因分析中呈现出相似的系统发育模式。在另外三个组中，检测到了共生基因的水平基因转移事件。具有可用基因组的 Paraburkholderia 菌株用于 nifHDK 和 fixABC 的互补分析，并证实了共生基因的明确系统发育位置。在 nod、nif 和 fix 基因的所有分析中，菌株被分为五个具有高自举支持的分支，允许在固氮结瘤 Paraburkholderia 中提出五个共生变种，分别命名为 mimosae、africana、tropicalis、atlantica 和 piptadeniae。讨论了每个共生变种内的系统发育推断。
