Frankia saprophytica sp. nov., an atypical, non-infective (Nod–) and non-nitrogen fixing (Fix–) actinobacterium isolated from Coriaria nepalensis root nodules

Strain CN3T, a Coriaria nepalensis isolate, appears to form hyphae and sporangia typical of members fo the genus Frankia . However, it failed to form vesicles, to reduce acetylene and to induce nodules on its original host plant. A polyphasic approach was used here to determine the taxonomic status of strain CN3T. The 16S rRNA gene sequence of strain CN3T showed the highest sequence identity with Frankia asymbiotica type strain M16386T (99.4 %). Digital DNA–DNA hybridization between strains CN3T and M16386T was 25.7 %, which is clearly below the accepted cut-off point of 70 %. The G+C content of DNA was 71.8 mol%. Whole-cell hydrolysates of strain CN3T were rich in meso-diaminopimelic acid. Cell-wall sugars were composed of galactose, glucose, mannose, rhamnose and traces of ribose. The polar lipid profile contained phosphatidylinositol, phosphatidylglycerol, diphosphatidylglycerol, phosphoglycolipids, phospholipid, six uncharacterized glycolipids and two uncharacterized lipids. The predominant menaquinone (>25 %) was MK-9(H6). Major fatty acids (>15 %) of strain CN3T consisted of iso-C16 : 0, C17 : 1ω8c and C15 : 0. Based on 16S rRNA gene phylogeny, genome sequence analysis and phenotypic results, strain CN3T (=DSM 105290T=CECT 9314T) is proposed to represent the type strain of a novel species, Frankia saprophytica sp. nov.