Frankia umida sp. nov., isolated from root nodules of Alnus glutinosa L.

strain Ag45/Mut15 was isolated from a root nodule of growing in a swamp at lake Grossensee, Germany. The strain forms root nodules on , in which it produces hyphae and clusters of N-fixing vesicles. N-fixing vesicles are also produced in nitrogen-free growth medium, in addition to hyphae and sporangia. The whole-cell hydrolysates of strain Ag45/Mut15 contained -diaminopimelic acid in the peptidoglycan and ribose, xylose, mannose, glucose, galactose and a trace of rhamnose as cell-wall sugars. The major polar lipids were phosphatidylglycerol, phosphatidylinositol, diphosphatidylglycerol and glyco-phospholipid. The predominant (>20 %) menaquinones were MK-9(H) and MK-9(H). The major fatty acid profile (>10 %) consisted of iso-C, C ω8 and C. Pairwise 16S rRNA gene distances showed that strain Ag45/Mut15 was most closely related to CpI1 and Frankia nodulisporulans with 16S rRNA gene similarity values of 0.001335 substitutions per site. An multilocus sequence analysis phylogeny based on , , , and amino acid sequences positioned the strain within cluster 1 of - and -nodulating species, close to F. nodulisporulans AgTrS and ARgP5. The digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values between the studied strain Ag45/Mut15 and all validly named species were below the defined threshold for prokaryotic species demarcation. F. nodulisporulans AgTrS, which cannot be cultivated , was found to be the closest phylogenetic neighbour to strain strain Ag45/Mut15 with dDDH and ANI values of 61.8 and 97 %, respectively. Strain Ag45/Mut15 was not able to sporulate in nodule tissues like strain AgTrS.Phenotypic, physiological and phylogenomic analyses confirmed the assignment of strain Ag45/Mut15 (=DSM 114737=LMG 326O1) to a novel species, with Ag45/Mut15 as type strain, for which the name sp. nov. is proposed.