Nick G, Paget E, Simonet P, Moiroud A, Normand P
Laboratoire d'Ecologie Microbienne du Sol, Bat. 741, URA CNRS 1450, Université Lyon I, Villeurbanne, France.
Mol Ecol. 1992 Oct;1(3):175-81. doi: 10.1111/j.1365-294x.1992.tb00173.x.
Repeated attempts at isolating the Frankia endophyte of Coriaria spp. have not yielded infective microbial cultures that could fulfil Koch's postulates. In order to circumvent the critical isolation step, nodule endophytes of Coriaria were characterized directly by means of specific amplification of nodule DNA (PCR) followed by sequencing of part of the 16S rDNA gene. Three closely related sequences were obtained from nodules originating from France, Mexico and New Zealand, containing unique sequences different from all other Frankia strains characterized so far. The sequences obtained were closest (with 5 or 6 substitutions) to those of Frankia alni and those of Casuarina-infective Frankia strains, respectively. Two nucleotides unique to the Coriaria endophyte sequences were used to define specific primers, resulting in a hybridization test that could discriminate between Frankia DNAs originating from Coriaria nodules and those recovered from all cultured Frankia strains tested. The endophytes of Coriaria thus appear to form a distinct Frankia lineage.
多次尝试分离马桑属植物的内生弗兰克氏菌均未获得能满足科赫法则的有感染力的微生物培养物。为了规避关键的分离步骤，直接通过对根瘤DNA进行特异性扩增（PCR），随后对16S rDNA基因的部分序列进行测序，对马桑属植物的根瘤内生菌进行了表征。从来自法国、墨西哥和新西兰的根瘤中获得了三个密切相关的序列，这些序列包含与迄今所表征的所有其他弗兰克氏菌菌株不同的独特序列。所获得的序列分别与桤木弗兰克氏菌和能感染木麻黄的弗兰克氏菌菌株的序列最为接近（有5个或6个替换位点）。马桑属植物内生菌序列特有的两个核苷酸被用于设计特异性引物，从而进行杂交试验，该试验能够区分源自马桑属植物根瘤的弗兰克氏菌DNA和从所有测试的培养弗兰克氏菌菌株中回收的DNA。因此，马桑属植物的内生菌似乎形成了一个独特的弗兰克氏菌谱系。
