Frankia colletiae sp. nov., a nitrogen-fixing actinobacterium isolated from Colletia cruciata

Abstract

A nitrogen-fixing actinobacterium strain (Cc1.17T) isolated from a root nodule of Colletia cruciata was subjected to polyphasic taxonomic studies. The strain was characterized by the presence of meso-diaminopimelic acid in its peptidoglycan, galactose, glucose, mannose, rhamnose, ribose and xylose as cell-wall sugars, phosphatidylinositol, diphosphatidylglycerol, glycophospholipids, phosphatidylglycerol, glycophospholipid and uncharacterized lipids as its polar lipids, and C16:0, iso-C16:0, C17: 1 ω9 and C18:1 ω9 as major fatty acids (>10%). Strain Cc1.17T showed 16S rRNA gene sequence similarities of 97.4–99.8% to validly named Frankia species. Phylogenetic trees based on 16S rRNA gene and genome sequences placed strain Cc1.17T in a new lineage within the genus Frankia. Digital DNA–DNA hybridization and average nucleotide identity values between strain Cc1.17T and its closest phylogenomic neighbours were well below the thresholds recommended for prokaryotic species delineation. Therefore, strain Cc1.17T (=DSM 43829T=CECT 9313T) merits recognition as the type strain of a new species for which the name Frankia colletiae sp. nov. is proposed.