Frankia torreyi sp. nov., the first actinobacterium of the genus Frankia Brunchorst 1886, 174AL isolated in axenic culture


Strain CpI1T was, in 1978, the first isolate of the genus Frankia to be obtained from Comptonia peregrina root nodules. In this study, a polyphasic approach was performed to identify the taxonomic position of strain CpI1T among the members of the genus Frankia. The strain contains meso-diaminopimelic acid as the diagnostic diamino acid and galactose, glucose, mannose, rhamnose, ribose and xylose as cell wall sugars. The polar lipids were found to consist of phosphatidylinositol, diphosphatidylglycerol, glycophospholipids, phosphatidylglycerol, an aminophospholipid and unidentified phospholipids and lipids. The predominant menaquinone was identified as MK-9 (H8), while the major fatty acid are iso-C16:0 and C17:1ω 8c. The 16S rRNA gene sequence identity varies from 97.4 to 99.6% with the type strains of currently described Frankia species. Phylogenetic analyses based on 16S rRNA gene sequences and multi-locus sequence analysis (MLSA) using atp1, ftsZ, dnaK, gyrA and secA gene sequences showed that strain CpI1T is closely related to Frankia alni ACN14aT. The genome size of strain CpI1T is 7.6 Mb with a digital DNA G+C content of 72.4%. Digital DNA:DNA hybridization (values between strain CpI1T and its close phylogenetic relative F. alni ACN14aT was 44.1%, well below the threshold of 70% for distinguishing between bacterial genomic species. Based on the phenotypic, phylogenetic and genomic data, strain CpI1T (= DSM44263T = CECT9035T) warrants classification as the type strain of a novel species, for which the name Frankia torreyi sp. nov. is proposed.


Molecular, Cellular and Biomedical Sciences

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Antonie van Leeuwenhoek



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